Sample records for kev auroral electrons

  1. Field aligned currents and the auroral spectrum below 1 keV

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.

    1973-01-01

    Measurements during auroral events were conducted with the aid of detectors flown aboard three Nike-Tomahawk rocket flights. The detectors used to measure the auroral spectrum below 1 keV consisted of electrostatic analyzers positioned in the rocket to measure particles moving up and down the magnetic field lines. The analyzers measured electrons and protons simultaneously during a given sweep.

  2. Electron currents associated with an auroral band

    NASA Technical Reports Server (NTRS)

    Spiger, R. J.; Anderson, H. R.

    1975-01-01

    Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed.

  3. Low-Altitude Satellite Measurements of Pulsating Auroral Electrons

    NASA Technical Reports Server (NTRS)

    Samara, M.; Michell, R. G.; Redmon, R. J.

    2015-01-01

    We present observations from the Defense Meteorological Satellite Program and Reimei satellites, where common-volume high-resolution ground-based auroral imaging data are available. These satellite overpasses of ground-based all-sky imagers reveal the specific features of the electron populations responsible for different types of pulsating aurora modulations. The energies causing the pulsating aurora mostly range from 3 keV to 20 keV but can at times extend up to 30 keV. The secondary, low-energy electrons (<1 keV) are diminished from the precipitating distribution when there are strong temporal variations in auroral intensity. There are often persistent spatial structures present inside regions of pulsating aurora, and in these regions there are secondary electrons in the precipitating populations. The reduction of secondary electrons is consistent with the strongly temporally varying pulsating aurora being associated with field-aligned currents and hence parallel potential drops of up to 1 kV.

  4. Auroral electron distribution function

    NASA Technical Reports Server (NTRS)

    Kaufmann, R. L.; Dusenbery, P. B.; Thomas, B. J.; Arnoldy, R. L.

    1978-01-01

    During a rocket flight over an active aurora, electron velocity distribution is studied in the 15-25 keV range. The results are then compared to optical observations made by all-sky cameras and a television system. A broad plateau produced by downcoming electrons was observed. Smaller plateaus were seen when the rocket was south of arcs evident in all-sky camera photographs. By extending to higher energies when the rocket passed out of auroral forms, the plateaus appeared to broaden. When the rocket left an arc or entered weak diffuse auroral structures, the plateaus shrank as the more energetic portions faded. When field-aligned rays were observed within the arcs, the plateau's high-velocity cutoff was found to fluctuate. The results indicate that the auroral plasma was very unstable above the rocket. It is suggested that plateaus are produced as an unstable plasma evolves toward a quasi-equilibrium state.

  5. Development and performance of a suprathermal electron spectrometer to study auroral precipitations

    NASA Astrophysics Data System (ADS)

    Ogasawara, Keiichi; Grubbs, Guy; Michell, Robert G.; Samara, Marilia; Stange, Jason L.; Trevino, John A.; Webster, James; Jahn, Jörg-Micha

    2016-05-01

    The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3-20 keV range for APDs, and 7 keV resolution for >20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker Flat Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.

  6. Development and performance of a suprathermal electron spectrometer to study auroral precipitations.

    PubMed

    Ogasawara, Keiichi; Grubbs, Guy; Michell, Robert G; Samara, Marilia; Stange, Jason L; Trevino, John A; Webster, James; Jahn, Jörg-Micha

    2016-05-01

    The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3-20 keV range for APDs, and 7 keV resolution for >20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker Flat Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.

  7. Development and Performance of a Suprathermal Electron Spectrometer to Study Auroral Precipitations

    NASA Technical Reports Server (NTRS)

    Ogasawara, Keiichi; Grubbs, Guy, II; Michell, Robert G.; Samara, Maria; Stange, Jason L.; Trevino, John A.; Webster, James; Jahn, Jorg-Micha

    2016-01-01

    The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3-20 keV range for APDs, and 7 keV resolution for greater than 20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker F1at Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.

  8. Development and performance of a suprathermal electron spectrometer to study auroral precipitations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ogasawara, Keiichi, E-mail: kogasawara@swri.edu; Stange, Jason L.; Trevino, John A.

    2016-05-15

    The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3−20 keV range for APDs, and 7 keV resolution for >20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation tomore » read-out and analyze the detector signals. MESP was launched from Poker Flat Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.« less

  9. Rocket measurements of electrons in a system of multiple auroral arcs

    NASA Technical Reports Server (NTRS)

    Boyd, J. S.; Davis, T. N.

    1977-01-01

    A Nike-Tomahawk rocket was launched into a system of auroral arcs northward of Poker Flat Research Range, Fairbanks, Alaska. The pitch-angle distribution of electrons was measured at 2.5, 5, and 10 keV and also at 10 keV on a separating forward section of the payload. The auroral activity appeared to be the extension of substorm activity centered to the east. The rocket crossed a westward-propagating fold in the brightest band. The electron spectrum was relatively hard through most of the flight, showing a peak in the range from 2.5 to 10 keV in the weaker aurora and below 5 keV in the brightest arc. The detailed structure of the pitch-angle distribution suggested that, at times, a very selective process was accelerating some electrons in the magnetic field direction, so that a narrow field-aligned component appeared superimposed on a more isotropic distribution. It is concluded that this process could not be a near-ionosphere field-aligned potential drop, although the more isotropic component may have been produced by a parallel electric field extending several thousand kilometers along the field line above the ionosphere.

  10. Very low frequency waves stimulated by an electron accelerator in the auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Holtet, J. A.; Pran, B. K.; Egeland, A.; Grandal, B.; Jacobsen, T. A.; Maehlum, B. N.; Troim, J.

    1981-01-01

    The sounding rocket, Polar 5, carrying a 10 keV electron accelerator in a mother-daughter configuration and other diagnostic instruments, was launched into a slightly disturbed ionosphere with weak auroral activity on February 1, 1976 from Northern Norway to study VLF wave phenomena. The rocket trajectory crossed two auroral regions: one, between 86 and 111 s flight time, and a secondary region between 230 and 330 s. The daughter, carrying the accelerator, was separated axially from the mother in a forward direction at an altitude of 90 km. The VLF experiment, carried by the mother payload, recorded both electromagnetic and electrostatic waves. The receiving antenna was an electric dipole, 0.3 m tip-to-tip, oriented 90 degrees to the rocket spin axis. The onboard particle detector recorded increased electron fluxes in the two auroral regions. A double peaked structure was observed in the fluxes of 4-5 and 12-27 keV electrons within the northern auroral form. The number density of thermal plasma varied during the flight, with maximum density within the main auroral region. To the north of this aurora a slow, steady decrease in the density was observed, with no enhancement in the region of the second aurora.

  11. Analysis of auroral particle fluxes

    NASA Technical Reports Server (NTRS)

    Chappell, C. R.

    1972-01-01

    The physical processes which describe the interaction of auroral electrons with the atmosphere appear to be more complex than just the Coulomb scattering of the incident primary electrons with a subsequent loss of energy. The comparison of the measured backscattered electron spectra with spectra predicted using a theoretical scattering calculation has led to a discrepancy for energies below about 1 to 2 keV. It was found that the very high ratio (100%) of backscattered to incident fluxes for these energies could be most reasonably explained by a parallel downward-directed electric field which prevents these lower energy electrons from entering the atmospheric scattering region. This parallel field with potential drop of about 1 keV is thought to have its origin in waveparticle interactions in the turbulent auroral ionosphere.

  12. Observations of waves artificially stimulated by an electron beam inside a region with auroral precipitation

    NASA Technical Reports Server (NTRS)

    Grandal, B.; Troim, J.; Maehlum, B.; Holtet, J. A.; Pran, B.

    1980-01-01

    Observations of waves stimulated by artificial injection inside an auroral arc by an electron accelerator mounted on the POLAR 5 sounding rocket are presented. The accelerator produced a pulsed electron beam with currents up to 130 mA and energies up to 10 keV; emissions after the end of beam injection were generated by perturbations in the ambient plasma near the accelerator during beam injection. These emissions were independent of the electron beam direction along the geomagnetic field. The high frequency emission observed after beam injection correlated with the passage through an auroral arc; the low frequency emissions after beam injection were concentrated in two bands below the lower hybrid frequency.

  13. Electron Pitch Angle Distributions Along Field Lines Connected to the Auroral Region from 25 to 1.2 RJ Measured by the Jovian Auroral Distributions Experiment-Electrons (JADE-E) on Juno

    NASA Astrophysics Data System (ADS)

    Allegrini, F.; Bagenal, F.; Bolton, S. J.; Bonfond, B.; Chae, K.; Clark, G. B.; Connerney, J. E. P.; Ebert, R. W.; Gladstone, R.; Hue, V.; Hospodarsky, G. B.; Kim, T. K. H.; Kurth, W. S.; Levin, S.; Louarn, P.; Mauk, B.; McComas, D. J.; Pollock, C. J.; Ranquist, D. A.; Reno, M. L.; Saur, J.; Szalay, J.; Thomsen, M. F.; Valek, P. W.; Wilson, R. J.

    2017-12-01

    The Jovian Auroral Distributions Experiment (JADE) on Juno provides critical in situ measurements of electrons and ions needed to understand the plasma distributions and processes that fill the Jovian magnetosphere and ultimately produce Jupiter's bright and dynamic aurora. JADE is an instrument suite that includes two essentially identical electron sensors (JADE-Es) and a single ion sensor (JADE-I). JADE-E measures electron energy distributions from 0.1 to 100 keV and provides detailed electron pitch angle distributions (PAD) at 7.5° resolution. Juno's trajectories in the northern hemisphere have allowed JADE to sample electron energy and pitch angle distributions on field lines connected to the auroral regions from as close as 1.2 RJ all the way to distances greater than 25 RJ. Here, we report on the evolution of these distributions. Specifically, the PADs change from mostly uniform at distances greater than 20 RJ, to butterfly from 18 to 12 RJ, to field aligned or pancake, depending on the energy, closer to Jupiter. Below 1.5 RJ, electron beams and loss cones are observed.

  14. Echo 2 - Observations at Fort Churchill of a 4-keV peak in low-level electron precipitation

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.; Hendrickson, R. A.; Winckler, J. R.

    1975-01-01

    The Echo 2 rocket flight launched from Fort Churchill, Manitoba, offered the opportunity to observe high-latitude low-level electron precipitation during quiet magnetic conditions. Although no visual aurora was evident at the time of the flight, an auroral spectrum sharply peaked at a few keV was observed to have intensities from 1 to 2 orders of magnitude lower than peaked spectra typically associated with bright auroral forms. There is a growing body of evidence that relates peaked electron spectra to discrete aurora. The Echo 2 observations show that whatever the mechanism for peaking the electron spectrum in and above discrete forms, it operates over a range of precipitation intensities covering nearly 3 orders of magnitude down to subvisual or near subvisual events.

  15. Sounding rocket study of auroral electron precipitation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McFadden, J.P.

    1985-01-01

    Measurement of energetic electrons in the auroral zone have proved to be one of the most useful tools in investigating the phenomena of auroral arc formation. This dissertation presents a detailed analysis of the electron data from two sounding rocket campaigns and interprets the measurements in terms of existing auroral models. The Polar Cusp campaign consisted of a single rocket launched from Cape Parry, Canada into the afternoon auroral zone at 1:31:13 UT on January 21, 1982. The results include the measurement of a narrow, magnetic field aligned electron flux at the edge of an arc. This electron precipitation wasmore » found to have a remarkably constant 1.2 eV temperature perpendicular to the magnetic field over a 200 to 900 eV energy range. The payload also made simultaneous measurements of both energetic electrons and 3-MHz plasma waves in an auroral arc. Analysis has shown that the waves are propagating in the upper hybrid band and should be generated by a positive slope in the parallel electron distribution. A correlation was found between the 3-MHz waves and small positive slopes in the parallel electron distribution but experimental uncertainties in the electron measurement were large enough to influence the analysis. The BIDARCA campaign consisted of two sounding rockets launched from Poker Flat and Fort Yukon, Alaska at 9:09:00 UT and 9:10:40 UT on February 7, 1984.« less

  16. Energetic electron precipitation and auroral morphology at the substorm recovery phase

    NASA Astrophysics Data System (ADS)

    Oyama, S. I.; Kero, A.; Rodger, C. J.; Clilverd, M. A.; Yoshizumi, M.; Partamies, N.; Turunen, E. S.; Tero, R.; Verronen, P. T.; Saito, S.

    2017-12-01

    It is well known that auroral patterns at the substorm recovery phase are characterized by diffuse or patch structures with intensity pulsation. According to satellite measurements and simulation studies, the precipitating electrons associated with these aurorae can reach or exceed energies of a few hundred keV through resonant wave-particle interactions in the magnetosphere. However, because of difficulty of simultaneous measurements, the dependency of energetic electron precipitation (EEP) on auroral morphological changes in the mesoscale has not been investigated to date. In order to study this dependency, we have analyzed data from the European Incoherent Scatter (EISCAT) radar, the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) riometer, collocated cameras, ground-based magnetometers, the Van Allen Probe satellites, Polar Operational Environmental Satellites (POES), and the Antarctic-Arctic Radiation-belt (Dynamic) Deposition-VLF Atmospheric Research Konsortium (AARDDVARK). Here we undertake a detailed examination of two case studies. The selected two events suggest that the highest energy of EEP on those days occurred with auroral patch formation from post-midnight to dawn, coinciding with the substorm onset at local midnight. Measurements of the EISCAT radar showed ionization as low as 65 km altitude, corresponding to EEP with energies of about 500 keV. Enhancements of the deep ionospheric ionization induced by the EEP modify the chemical-reaction balance involving atmospheric minor species such as NOx and HOx. These species may cause reduction in the ozone density at the ionization altitude or the lower region where these species are transported by the vertical convection in the dynamics. Since the EEP is a typical phenomenon at the substorm recovery phase, the ozone density depletion may be a frequent signature although our understanding has not yet reached the maturity of the mechanism behind these evidences. This presentation will discuss the

  17. Changes in the Martian atmosphere induced by auroral electron precipitation

    NASA Astrophysics Data System (ADS)

    Shematovich, V. I.; Bisikalo, D. V.; Gérard, J.-C.; Hubert, B.

    2017-09-01

    Typical auroral events in the Martian atmosphere, such as discrete and diffuse auroral emissions detected by UV spectrometers onboard ESA Mars Express and NASA MAVEN, are investigated. Auroral electron kinetic energy distribution functions and energy spectra of the upward and downward electron fluxes are obtained by electron transport calculations using the kinetic Monte Carlo model. These characteristics of auroral electron fluxes make it possible to calculate both the precipitation-induced changes in the atmosphere and the observed manifestations of auroral events on Mars. In particular, intensities of discrete and diffuse auroral emissions in the UV and visible wavelength ranges (Soret et al., 2016; Bisikalo et al., 2017; Gérard et al., 2017). For these conditions of auroral events, the analysis is carried out, and the contribution of the fluxes of precipitating electrons to the heating and ionization of the Martian atmosphere is estimated. Numerical calculations show that in the case of discrete auroral events the effect of the residual crustal magnetic field leads to a significant increase in the upward fluxes of electrons, which causes a decrease in the rates of heating and ionization of the atmospheric gas in comparison with the calculations without taking into account the residual magnetic field. It is shown that all the above-mentioned impact factors of auroral electron precipitation processes should be taken into account both in the photochemical models of the Martian atmosphere and in the interpretation of observations of the chemical composition and its variations using the ACS instrument onboard ExoMars.

  18. Artificial stimulation of auroral electron acceleration by intense field aligned currents

    NASA Technical Reports Server (NTRS)

    Holmgren, G.; Bostrom, R.; Kelley, M. C.; Kintner, P. M.; Lundin, R.; Bering, E. A.; Sheldon, W. R.; Fahleson, U. V.

    1979-01-01

    A cesium-doped high explosion was detonated at 165 km altitude in the auroral ionosphere during quiet conditions. An Alfven wave pulse with a 200-mV/m electric field was observed, with the peak occurring 135 ms after the explosion at a distance of about 1 km. The count rate of fixed energy 2-keV electron detectors abruptly increased at 140 ms, peaked at 415 ms, and indicated a downward field-aligned beam of accelerated electrons. An anomalously high-field aligned beam of backscattered electrons was also detected. The acceleration is interpreted as due to production of an electrostatic shock or double layer between 300 and 800 km altitude. The structure was probably formed by an instability of the intense field-aligned currents in the Alfven wave launched by the charge-separation electric field due to the explosion.

  19. Excitation of whistler waves by reflected auroral electrons

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Dillenburg, D.; Ziebell, L. F.; Freund, H. P.

    1983-01-01

    Excitation of electron waves and whistlers by reflected auroral electrons which possess a loss-cone distribution is investigated. Based on a given magnetic field and density model, the instability problem is studied over a broad region along the auroral field lines. This region covers altitudes ranging from one quarter of an earth radius to five earth radii. It is found that the growth rate is significant only in the region of low altitude, say below the source region of the auroral kilometric radiation. In the high altitude region the instability is insignificant either because of low refractive indices or because of small loss cone angles.

  20. Acceleration of auroral electrons in parallel electric fields

    NASA Technical Reports Server (NTRS)

    Kaufmann, R. L.; Walker, D. N.; Arnoldy, R. L.

    1976-01-01

    Rocket observations of auroral electrons are compared with the predictions of a number of theoretical acceleration mechanisms that involve an electric field parallel to the earth's magnetic field. The theoretical models are discussed in terms of required plasma sources, the location of the acceleration region, and properties of necessary wave-particle scattering mechanisms. We have been unable to find any steady state scatter-free electric field configuration that predicts electron flux distributions in agreement with the observations. The addition of a fluctuating electric field or wave-particle scattering several thousand kilometers above the rocket can modify the theoretical flux distributions so that they agree with measurements. The presence of very narrow energy peaks in the flux contours implies a characteristic temperature of several tens of electron volts or less for the source of field-aligned auroral electrons and a temperature of several hundred electron volts or less for the relatively isotropic 'monoenergetic' auroral electrons. The temperature of the field-aligned electrons is more representative of the magnetosheath or possibly the ionosphere as a source region than of the plasma sheet.

  1. Energy flux and characteristic energy of an elemental auroral structure

    NASA Technical Reports Server (NTRS)

    Lanchester, B. S.; Palmer, J. R.; Rees, M. H.; Lummerzheim, D.; Kaila, K.; Turunen, T.

    1994-01-01

    Electron density profiles acquired with the EISCAT radar at 0.2 s time resolution, together with TV images and photometric intensities, were used to study the characteristics of thin (less than 1 km) auroral arc structures that drifted through the field of view of the instruments. It is demonstrated that both high time and space resolution are essential for deriving the input parameters of the electron flux responsible for the elemental auroral structures. One such structure required a 400 mW/sq m (erg/sq cm s) downward energy flux carried by an 8 keV monochromatic electron flux equivalent to a current density of 50 micro Angstrom/sq m.

  2. The auroral current circuit and field-aligned currents observed by FAST

    NASA Astrophysics Data System (ADS)

    Elphic, R. C.; Bonnell, J. W.; Strangeway, R. J.; Kepko, L.; Ergun, R. E.; McFadden, J. P.; Carlson, C. W.; Peria, W.; Cattell, C. A.; Klumpar, D.; Shelley, E.; Peterson, W.; Moebius, E.; Kistler, L.; Pfaff, R.

    FAST observes signatures of small-scale downward-going current at the edges of the inverted-V regions where the primary (auroral) electrons are found. In the winter pre-midnight auroral zone these downward currents are carried by upward flowing low- and medium-energy (up to several keV) electron beams. FAST instrumentation shows agreement between the current densities inferred from both the electron distributions and gradients in the magnetic field. FAST data taken near apogee (˜4000-km altitude) commonly show downward current magnetic field deflections consistent with the observed upward flux of ˜109 electrons cm-2 s-1, or current densities of several µA m-2. The electron, field-aligned current and electric field signatures indicate the downward currents may be associated with “black aurora” and auroral ionospheric cavities. The field-aligned voltage-current relationship in the downward current region is nonlinear.

  3. Electrodynamic response of the middle atmosphere to auroral pulsations

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Croskey, C. L.; Hale, L. C.; Mitchell, J. D.; Barcus, J. R.

    1990-01-01

    The MAC/EPSILON observational campaign encompassed the use of two Nike Orion rocket payloads which studied the effects of auroral energetics on the middle atmosphere. While one payload was launched during the recovery phase of a moderate magnetic substorm, during fairly stable auroral conditions, the other was launched during highly active postbreakup conditions during which Pc5 pulsations were in progress. The energetic radiation of the first event was composed almost entirely of relativistic electrons below 200 keV, while that of the second was dominated by much softer electrons whose high X-ray fluxes exceeded the cosmic ray background as an ionizing source down to below 30 km.

  4. The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs

    NASA Astrophysics Data System (ADS)

    Dahlgren, H.; Semeter, J. L.; Marshall, R. A.; Zettergren, M.

    2013-07-01

    High-resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures of the corresponding energy dispersions are more commonly known as field-aligned bursts. In this paper, observations of auroral flames obtained at 50 frames/s with a scientific-grade Complementary Metal Oxide Semiconductor (CMOS) sensor (30° × 30° field of view, 30 m resolution at 120 km) are used to provide insight into the nature of the precipitating electrons similar to high-resolution particle detectors. Thanks to the large field of view and high spatial resolution of this system, it is possible to obtain a first-order estimate of the temporal evolution in altitude of the volume emission rate from a single sensor. The measured volume emission rates are compared with the sum of modeled eigenprofiles obtained for a finite set of electron beams with varying energy provided by the TRANSCAR auroral flux tube model. The energy dispersion signatures within each auroral ray can be analyzed in detail during a fraction of a second. The evolution of energy and flux of the precipitation shows precipitation spanning over a large range of energies, with the characteristic energy dropping from 2.1 keV to 0.87 keV over 0.2 s. Oscillations at 2.4 Hz in the magnetic zenith correspond to the period of the auroral flames, and the acceleration is believed to be due to Alfvenic wave interaction with electrons above the ionosphere.

  5. Field-aligned currents and the auroral electrojet

    NASA Technical Reports Server (NTRS)

    Cahill, L. J.; Potter, W. E.; Kintner, P. M.; Arnoldy, R. L.; Choy, L. W.

    1974-01-01

    A Nike Tomahawk with fields and particles payload was launched on Nov. 18, 1970, over a strong westward electrojet current and auroral forms moving rapidly to the east. Electron fluxes moving up and down the magnetic field lines were measured. Upward-moving electrons below 1-keV energy were dominant and were equivalent to a net downward electric current that fluctuated between .2 and .6 microamp/sq m during the flight above 130 km. As the rocket traversed this broad region of downward electric current over and to the north of the auroral forms, the horizontal electric field slowly rotated from east to west. The magnetic measurements indicate that the westward electrojet was a horizontal sheet of current several hundred kilometers in north-south extent.

  6. Observations of Interchange Between Acceleration and Thermalization Processes in Auroral Electrons. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Pongratz, M. B.

    1972-01-01

    The results of high time-resolution measurements of energetic electrons in an auroral break up are presented. Electrons with energies from 500 eV to over 100 keV and pitch angles from 0 to 150 deg were detected with two detectors onboard sounding rocket 18:63 UE. Complete energy spectra were taken every 0.1 seconds. The procedure for cleaning and activating the BeCu dynodes of a small, rugged, high gain electron multiplier is described. A theoretical study of the energy-angular response of a spherical plate electrostatic analyzer is compared to experimental results. An energy spectrum unfolding technique which does not require the assumption of a histogram-type energy spectrum is presented. A method of determining sounding rocket orientation from the output of a single magnetometer is described.

  7. The relationship between diffuse auroral and plasma sheet electron distributions near local midnight

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schumaker, T.L.; Gussenhoven, M.S.; Hardy, D.A.

    1989-08-01

    A study of the relationship between diffuse auroral and plasma sheet electron distributions in the energy range from 50 eV to 20 keV in the midnight region was conducted using data from the P78-1 and SCATHA satellites. From 1 1/2 years of data, 14 events were found where the polar-orbiting P78-1 satellite and the near-geosynchronous SCATHA satellite were approximately on the same magnetic field line simultaneously, with SCATHA in the plasma sheet and P78-1 in the diffuse auroral region. For all cases the spectra from the two satellites are in good quantitative agreement. For 13 of the 14 events themore » pitch angle distribution measured at P78-1 was isotropic for angles mapping into the loss cone at the SCATHA orbit. For one event the P78-1 electron flux decreased with pitch angle toward the field line direction. At SCATHA the distributions outside the loss cone were most commonly butterfly or pancake, although distributions peaked toward the field line were sometimes observed at energies below 1 keV. Electron distributions, as measured where there is isotropy within the loss cone but anisotropy outside the loss cone, are inconsistent with current theories for the scattering of cone for the distribution measured at SCATHA, the electron precipitation lifetimes were calculated for the 14 events. Because the distributions are anisotropic at pitch angles away from the loss cone, the calculated lifetimes significantly exceed the lifetimes in the limit when the flu is isotropic at all pitch angles. The computed precipitation lifetimes are found to be weakly dependent on magnetic activity. The average lifetimes exceed those for the case of isotropy at all pitch angles by a factor between 2 and 3 for {ital Kp}{le}2 and approximately 1.5 for {ital Kp}{gt}2. {copyright} American Geophysical Union 1989« less

  8. Field-aligned particle currents near an auroral arc.

    NASA Technical Reports Server (NTRS)

    Choy, L. W.; Arnoldy, R. L.; Potter, W.; Kintner, P.; Cahill, L. J., Jr.

    1971-01-01

    A Nike-Tomahawk rocket equipped to measure electric and magnetic fields and charged particles from a few eV to several hundred keV energy was flown into an auroral band on April 11, 1970. The purpose of this flight was to obtain evidence of the low-energy electrons and protons that constitute a field-aligned sheet current, and also to obtain the magnetic signature of such a current and the electric field in and near the auroral-arc electric current system. Particular attention was given to a sudden increase in the field-aligned current associated with a prior sudden increase in the electric field and a sudden change in the magnetic field, all occurring near the edge of a visual auroral arc. Data obtained are discussed and analyzed; they present an important contribution to the problem of mapping of atmospheric auroral phenomena to the magnetospheric equatorial plane.

  9. Accaleration of Electrons of the Outer Electron Radiation Belt and Auroral Oval Dynamics

    NASA Astrophysics Data System (ADS)

    Antonova, Elizaveta; Ovchinnikov, Ilya; Riazantseva, Maria; Znatkova, Svetlana; Pulinets, Maria; Vorobjev, Viachislav; Yagodkina, Oksana; Stepanova, Marina

    2016-07-01

    We summarize the results of experimental observations demonstrating the role of auroral processes in the formation of the outer electron radiation belt and magnetic field distortion during magnetic storms. We show that the auroral oval does not mapped to the plasma sheet proper (region with magnetic field lines stretched in the tailward direction). It is mapped to the surrounding the Earth plasma ring in which transverse currents are closed inside the magnetosphere. Such currents constitute the high latitude continuation of the ordinary ring current. Mapping of the auroral oval to the region of high latitude continuation of the ordinary ring current explains the ring like shape of the auroral oval with finite thickness near noon and auroral oval dynamics during magnetic storms. The auroral oval shift to low latitudes during storms. The development of the ring current produce great distortion of the Earth's magnetic field and corresponding adiabatic variations of relativistic electron fluxes. Development of the asymmetric ring current produce the dawn-dusk asymmetry of such fluxes. We analyze main features of the observed processes including formation of sharp plasma pressure profiles during storms. The nature of observed pressure peak is analyzed. It is shown that the observed sharp pressure peak is directly connected with the creation of the seed population of relativistic electrons. The possibility to predict the position of new radiation belt during recovery phase of the magnetic storm using data of low orbiting and ground based observations is demonstrated.

  10. The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae

    NASA Technical Reports Server (NTRS)

    Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Waite, J. H.; Cravens, T.; Ford, P.

    2007-01-01

    The discovery in XMM-Newton X-ray data of X-ray emission above 2 keV from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

  11. Electron acceleration in downward auroral field-aligned currents

    NASA Astrophysics Data System (ADS)

    Cran-McGreehin, Alexandra P.; Wright, Andrew N.

    2005-10-01

    The auroral downward field-aligned current is mainly carried by electrons accelerated up from the ionosphere into the magnetosphere along magnetic field lines. Current densities are typically of the order of a few μ Am-2, and the associated electrons are accelerated to energies of several hundred eV up to a few keV. This downward current has been modeled by Temerin and Carlson (1998) using an electron fluid. This paper extends that model by describing the electron populations via distribution functions and modeling all of the F region. We assume a given ion density profile, and invoke quasi-neutrality to solve for the potential along the field line. Several important locations and quantities emerge from this model: the ionospheric trapping point, below which the ionospheric population is trapped by an ambipolar electric field; the location of maximum E∥, of the order of a few mVm-1, which lies earthward of the B/n peak; the acceleration region, located around the B/n peak, which normally extends between altitudes of 500 and 3000 km; and the total potential increase along the field line, of the order of a few hundred V up to several kV. The B/n peak is found to be the central factor determining the altitude and magnitude of the accelerating potential required. Indeed, the total potential drop is found to depend solely on the equilibrium properties in the immediate vicinity of the B/n peak.

  12. The first year of observations of Jupiter's magnetosphere from Juno's Jovian Auroral Distributions Experiment (JADE)

    NASA Astrophysics Data System (ADS)

    Valek, P. W.; Allegrini, F.; Angold, N. G.; Bagenal, F.; Bolton, S. J.; Chae, K.; Connerney, J. E. P.; Ebert, R. W.; Gladstone, R.; Kim, T. K. H.; Kurth, W. S.; Levin, S.; Louarn, P.; Loeffler, C. E.; Mauk, B.; McComas, D. J.; Pollock, C. J.; Reno, M. L.; Szalay, J. R.; Thomsen, M. F.; Weidner, S.; Wilson, R. J.

    2017-12-01

    Juno observations of the Jovian plasma environment are made by the Jovian Auroral Distributions Experiment (JADE) which consists of two nearly identical electron sensors - JADE-E - and an ion sensor - JADE-I. JADE-E measures the electron distribution in the range of 100 eV to 100 keV and uses electrostatic deflection to measure the full pitch angle distribution. JADE-I measures the composition separated energy per charge in the range of 10 eV / q to 46 keV / q. The large orbit - apojove 110 Rj, perijove 1.05 Rj - allows JADE to periodically cross through the magnetopause into the magnetosheath, transverse the outer, middle, and inner magnetosphere, and measures the plasma population down to the ionosphere. We present here in situ plasma observations of the Jovian magnetosphere and topside ionosphere made by the JADE instrument during the first year in orbit. Dawn-side crossings of the plasmapause have shown a general dearth of heavy ions except during some intervals at lower magnetic latitudes. Plasma disk crossings in the middle and inner magnetosphere show a mixture of heavy and light ions. During perijove crossings at high latitudes when Juno was connected to the Io torus, JADE-I observed heavy ions with energies consistent with a corotating pickup population. In the auroral regions the core of the electron energy distribution is generally from about 100 eV when on field lines that are connected to the inner plasmasheet, several keVs when connected to the outer plasmasheet, and tens of keVs when Juno is over the polar regions. JADE has observed upward electron beams and upward loss cones, both in the north and south auroral regions, and downward electron beams in the south. Some of the beams are of short duration ( 1 s) implying that the magnetosphere has a very fine spatial and/or temporal structure within the auroral regions. Joint observations with the Waves instrument have demonstrated that the observed loss cone distributions provide sufficient growth rates

  13. Modulation of auroral electron fluxes in the frequency range 50 kHz to 10 MHz

    NASA Technical Reports Server (NTRS)

    Spiger, R. J.; Murphree, J. S.; Anderson, H. R.; Loewenstein, R. F.

    1976-01-01

    A sounding rocket-borne electron detector of high time resolution is used to search for modulation of auroral electron fluxes in the frequency range 50 kHz to 10 MHz and energy range 5-7 keV. Data were telemetered to ground via a 93-kHz subcarrier. A cross-correlation analysis of the data collected indicates low-level modulation near the detection threshold of the instrument. Two U-1 events are observed which are interpreted as indications of modulation. The two modulation events occur during a period of increasing flux for a region marking the boundary between two current sheets detected by the payload magnetometer. The strongest argument against interference contamination is the lack of any observable modulation at times other than those mentioned in the study.

  14. Electron precipitation in the post midnight sector of the auroral zones. [on the Explorer 40 satellite

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Saflekos, N. A.; Ackerson, K. L.

    1975-01-01

    Comprehensive measurements of the angular distributions and energy spectra of electron intensities with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported. These are for the post-midnight sector of the auroral zones during the high-intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for energetic electrons with E greater than 45 keV were examined. No evidences of maxima in the differential energy spectra or of strongly field-aligned currents which are indicative of quasi-static electric fields aligned parallel to the geomagnetic field were found. Precipitation of low-energy electron intensities fluctuated on time scales greater than 2 seconds as viewed at the satellite position. This precipitation was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone.

  15. Simultaneous total electron content and all-sky camera measurements of an auroral arc

    NASA Astrophysics Data System (ADS)

    Kintner, P. M.; Kil, H.; Deehr, C.; Schuck, P.

    2002-07-01

    We present an example of Global Positioning System (GPS) derived total electron content (TEC) and all-sky camera (ASC) images that show increases of TEC by ~10 × 1016 electrons m-2 (10 TEC units) occurring simultaneously with auroral light in ASC images. The TEC example appears to be an E region density enhancement produced by two discrete auroral arcs occurring in the late morning auroral oval at 1000 LT. This suggests that GPS signal TEC measurements can be used to detect individual auroral arcs and that individual discrete auroral arcs are responsible for some high-latitude phase scintillations. The specific auroral feature detected was a poleward moving auroral form believed to occur in the polar cap where the ionosphere is convecting antisunward. The magnitude of the rate of change of TEC (dTEC/dt) is comparable to that previously reported. However, the timescales associated with the event, the order of 1 min, suggest that the data sampling technique commonly used by chain GPS TEC receivers (averaging and time decimation) will undersample E region TEC perturbations produced by active auroral displays. The localized nature of this example implies that L1 ranging errors of at least 1.6 m will be introduced by auroral arcs into systems relying on differential GPS for navigation or augmentation. Although the TEC and auroral arcs presented herein occurred in the late morning auroral oval, we expect that the effects of discrete auroral arcs on GPS TEC and subsequent ranging errors should occur at all local times. Furthermore, GPS receivers can be used to detect individual discrete arcs.

  16. The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae

    NASA Technical Reports Server (NTRS)

    Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Gladstone, G. R.; Waite, J. H.; Cravens, T.; Ford, P.

    2007-01-01

    The discovery in XMM-Newton X-ray data of X-ray emission above 2 keY from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

  17. Validation of Ground-based Optical Estimates of Auroral Electron Precipitation Energy Deposition

    NASA Astrophysics Data System (ADS)

    Hampton, D. L.; Grubbs, G. A., II; Conde, M.; Lynch, K. A.; Michell, R.; Zettergren, M. D.; Samara, M.; Ahrns, M. J.

    2017-12-01

    One of the major energy inputs into the high latitude ionosphere and mesosphere is auroral electron precipitation. Not only does the kinetic energy get deposited, the ensuing ionization in the E and F-region ionosphere modulates parallel and horizontal currents that can dissipate in the form of Joule heating. Global models to simulate these interactions typically use electron precipitation models that produce a poor representation of the spatial and temporal complexity of auroral activity as observed from the ground. This is largely due to these precipitation models being based on averages of multiple satellite overpasses separated by periods much longer than typical auroral feature durations. With the development of regional and continental observing networks (e.g. THEMIS ASI), the possibility of ground-based optical observations producing quantitative estimates of energy deposition with temporal and spatial scales comparable to those known to be exhibited in auroral activity become a real possibility. Like empirical precipitation models based on satellite overpasses such optics-based estimates are subject to assumptions and uncertainties, and therefore require validation. Three recent sounding rocket missions offer such an opportunity. The MICA (2012), GREECE (2014) and Isinglass (2017) missions involved detailed ground based observations of auroral arcs simultaneously with extensive on-board instrumentation. These have afforded an opportunity to examine the results of three optical methods of determining auroral electron energy flux, namely 1) ratio of auroral emissions, 2) green line temperature vs. emission altitude, and 3) parametric estimates using white-light images. We present comparisons from all three methods for all three missions and summarize the temporal and spatial scales and coverage over which each is valid.

  18. SA13B-1900 Auroral Charging of the International Space Station

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Chandler, Michael O.; Wright, Kenneth H., Jr.

    2011-01-01

    Electrostatic potential variations of the International Space Station (ISS) relative to the space plasma environment are dominated by interaction of the negatively grounded 160 volt US photovoltaic power system with the plasma environment in sunlight and inductive potential variations across the ISS structure generated by motion of the vehicle across the Earth's magnetic field. Auroral charging is also a source of potential variations because the 51.6? orbital inclination of ISS takes the vehicle to sufficiently high magnetic latitudes to encounter precipitating electrons during geomagnetic storms. Analysis of auroral charging for small spacecraft or isolated insulating regions on ISS predict rapid charging to high potentials of hundreds of volts but it has been thought that the large capacitance of the entire ISS structure on the order of 0.01 F will limit frame potentials to less than a volt when exposed to auroral conditions. We present three candidate auroral charging events characterized by transient ISS structure potentials varying from approximately 2 to 17 volts. The events occur primarily at night when the solar arrays are unbiased and cannot therefore be due to solar array current collection. ISS potential decreases to more negative values during the events indicating electron current collection and the events are always observed at the highest latitudes along the ISS trajectory. Comparison of the events with integral >30 keV electron flux measurements from NOAA TIROS spacecraft demonstrate they occur within regions of precipitating electron flux at levels consistent with the energetic electron thresholds reported for onset of auroral charging of the DMSP and Freja satellites. In contrast to the DMSP and Freja events, one of the ISS charging events occur in sunlight.

  19. A Comparative Study of Spectral Auroral Intensity Predictions From Multiple Electron Transport Models

    NASA Astrophysics Data System (ADS)

    Grubbs, Guy; Michell, Robert; Samara, Marilia; Hampton, Donald; Hecht, James; Solomon, Stanley; Jahn, Jorg-Micha

    2018-01-01

    It is important to routinely examine and update models used to predict auroral emissions resulting from precipitating electrons in Earth's magnetotail. These models are commonly used to invert spectral auroral ground-based images to infer characteristics about incident electron populations when in situ measurements are unavailable. In this work, we examine and compare auroral emission intensities predicted by three commonly used electron transport models using varying electron population characteristics. We then compare model predictions to same-volume in situ electron measurements and ground-based imaging to qualitatively examine modeling prediction error. Initial comparisons showed differences in predictions by the GLobal airglOW (GLOW) model and the other transport models examined. Chemical reaction rates and radiative rates in GLOW were updated using recent publications, and predictions showed better agreement with the other models and the same-volume data, stressing that these rates are important to consider when modeling auroral processes. Predictions by each model exhibit similar behavior for varying atmospheric constants, energies, and energy fluxes. Same-volume electron data and images are highly correlated with predictions by each model, showing that these models can be used to accurately derive electron characteristics and ionospheric parameters based solely on multispectral optical imaging data.

  20. Scaled Experiment to Investigate Auroral Kilometric Radiation Mechanisms in the Presence of Background Electrons

    NASA Astrophysics Data System (ADS)

    McConville, S. L.; Ronald, K.; Speirs, D. C.; Gillespie, K. M.; Phelps, A. D. R.; Cross, A. W.; Bingham, R.; Robertson, C. W.; Whyte, C. G.; He, W.; King, M.; Bryson, R.; Vorgul, I.; Cairns, R. A.; Kellett, B. J.

    2014-05-01

    Auroral Kilometric Radiation (AKR) emissions occur at frequencies ~300kHz polarised in the X-mode with efficiencies ~1-2% [1,2] in the auroral density cavity in the polar regions of the Earth's magnetosphere, a region of low density plasma ~3200km above the Earth's surface, where electrons are accelerated down towards the Earth whilst undergoing magnetic compression. As a result of this magnetic compression the electrons acquire a horseshoe distribution function in velocity space. Previous theoretical studies have predicted that this distribution is capable of driving the cyclotron maser instability. To test this theory a scaled laboratory experiment was constructed to replicate this phenomenon in a controlled environment, [3-5] whilst 2D and 3D simulations are also being conducted to predict the experimental radiation power and mode, [6-9]. The experiment operates in the microwave frequency regime and incorporates a region of increasing magnetic field as found at the Earth's pole using magnet solenoids to encase the cylindrical interaction waveguide through which an initially rectilinear electron beam (12A) was accelerated by a 75keV pulse. Experimental results showed evidence of the formation of the horseshoe distribution function. The radiation was produced in the near cut-off TE01 mode, comparable with X-mode characteristics, at 4.42GHz. Peak microwave output power was measured ~35kW and peak efficiency of emission ~2%, [3]. A Penning trap was constructed and inserted into the interaction waveguide to enable generation of a background plasma which would lead to closer comparisons with the magnetospheric conditions. Initial design and measurements are presented showing the principle features of the new geometry.

  1. Local-time survey of plasma at low altitudes over the auroral zones.

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Ackerson, K. L.

    1972-01-01

    Local-time survey of the low-energy proton and electron intensities precipitated into the earth's atmosphere over the auroral zones during periods of magnetic quiescence. This survey was constructed by selecting a typical individual satellite crossing of this region in each of eight local-time sectors from a large library of similar observations with the polar-orbiting satellite Injun 5. The trapping boundary for more-energetic electron intensities, E greater than 45 keV, was found to be a 'natural coordinate' for delineating the boundary between the two major types of lower-energy, 50 less than or equal to E less than or equal to 15,000 eV, electron precipitation commonly observed over the auroral zones at low altitudes. Poleward of this trapping boundary inverted 'V' electron precipitation bands are observed in all local-time sectors. These inverted 'V' electron bands in the evening and midnight sectors are typically more energetic and have greater latitudinal widths than their counterparts in the noon and morning sectors. In general, the main contributors to the electron energy influx into the earth's atmosphere over the auroral zones are the electron inverted 'V' precipitation poleward of the trapping boundary in late evening, the plasma-sheet electron intensities equatorward of this boundary in early morning, and both of these precipitation events near local midnight.

  2. Auroral x-ray imaging from high- and low-Earth orbit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McKenzie, D.L.; Gorney, D.J.; Imhof, W.L.

    Observations of bremsstrahlung x rays emitted by energetic electrons impacting the Earth's atmosphere can be used for remotely sensing the morphology, intensity, and energy spectra of electron precipitation from the magnetosphere. The utility of the technique is derived from the broad energy range of observable x rays (2 to > 100 KeV), the simple emission process, the large x-ray mean free path in the atmosphere, and negligible background. Two auroral x-ray imagers, developed for future spaceflights, are discussed. The Polar Ionospheric X-Ray Imaging Experiment is scheduled for launch on the NASA International Solar-Terrestrial Physics/Global Geospace Science program POLAR satellite inmore » 1994. The POLAR orbit, with an apogee and perigee of 9 and 1.8 R[sub e] (Earth radii), respectively, affords the opportunity to image the aurora from a high altitude above the north pole continuously for several hours. The Magnetospheric Atmospheric X-Ray Imaging Experiment (MAXIE) was launched aboard the NOAA-I satellite on August 8, 1993. The 800-km polar orbit passes over both the northern and southern auroral zones every 101 min. MAXIE will be capable of obtaining multiple images of the same auroral region during a single satellite orbit. The experimental approaches used to exploit these very different orbits for remote sensing of the Earth's auroral zones are emphasized.« less

  3. Auroral electrojets and evening sector electron dropouts at synchronous orbit

    NASA Technical Reports Server (NTRS)

    Erickson, K. N.; Winckler, J. R.

    1973-01-01

    Evidence is presented in support of the concept that, during magnetospheric substorms, ionospheric auroral electrojet currents are directly coupled to the proton partial ring current in the outer magnetosphere. It has been found that for sufficiently isolated substorms the timing of the start of the electron dropout and of its maximum depression is in good agreement with the start and maximum of electrojet activity as indicated by the auroral electrojet index. This correlation suggests a direct coupling between the electrojet currents and the proton partial ring current.

  4. Coordinated measurements of auroral processes at Saturn from the Cassini spacecraft and HST

    NASA Astrophysics Data System (ADS)

    Mitchell, D. G.; Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.; Krupp, N.; Saur, J.; Mauk, B. A.; Carbary, J. F.; Krimigis, S. M.; Brandt, P. C.; Dougherty, M. K.; Clarke, J. T.; Nichols, J. D.; Gerard, J.; Grodent, D.; Pryor, W. R.; Bunce, E. J.; Crary, F. J.

    2008-12-01

    One of the primary Cassini mission objectives at Saturn is to characterize Saturn's aurora-its spatial morphology, associated particle energization, radio wave generation, and magnetospheric currents, relationship with solar wind pressure and magnetic field, and its large scale mapping to the magnetosphere. By design, the Cassini orbital tour included high inclination and low periapsis orbits late in the prime mission specifically to address many of these topics. In this presentation, we will provide a snapshot of the current state of our investigation into the relationship between magnetospheric measurements of particles and fields, and the aurora. For in situ data, we will show measurements of upward traveling light ion conics (~30 keV to 200 keV), often accompanied by electron beams (<20 keV to ~1 MeV) and enhanced broadband noise (10 Hz to a few kHz), throughout the outer magnetosphere on field lines that nominally map from well into the polar cap (dipole L > 50) to well into the closed field region (dipole L < 10). Sometimes the particle phenomena and the broadband noise occur in pulses of roughly five-minute duration, separated by tens of minutes. At other times they are relatively steady over an hour or more. Magnetic signatures associated with some of the pulsed events are consistent with field aligned current structures. Correlative observations of solar wind (Cassini) and aurora (HST) have established a strong relationship between solar wind pressure and auroral activity (brightness) (Crary et al., Nature, 2005; Clarke et al., JGR, 2008). A similar correspondence between bright auroral arcs and ring current ion acceleration will be shown here. So while some auroral forms seem to be associated with the open/closed field boundary (i.e. in the cusp-Bunce et al., JGR, 2008), we also demonstrate that under some magnetospheric conditions for which protons and oxygen ions are accelerated once per Saturn magnetosphere rotation at a preferred local time between

  5. Problem of Auroral Oval Mapping and Multiscale Auroral Structures

    NASA Astrophysics Data System (ADS)

    Antonova, Elizaveta; Stepanova, Marina; Kirpichev, Igor; Vovchenko, Vadim; Vorobjev, Viachislav; Yagodkina, Oksana

    The problem of the auroral oval mapping to the equatorial plane is reanalyzed taking into account the latest results of the analysis of plasma pressure distribution at low altitudes and at the equatorial plane. Statistical pictures of pressure distribution at low latitudes are obtained using data of DMSP observations. We obtain the statistical pictures of pressure distribution at the equatorial plane using data of THEMIS mission. Results of THEMIS observations demonstrate the existence of plasma ring surrounding the Earth at geocentric distances from ~6 till ~12Re. Plasma pressure in the ring is near to isotropic and its averaged values are larger than 0.2 nPa. We take into account that isotropic plasma pressure is constant along the field line and that the existence of field-aligned potential drops in the region of the acceleration of auroral electrons leads to pressure decrease at low altitudes. We show that most part of quite time auroral oval does not map to the real plasma sheet. It maps to the surrounding the Earth plasma ring. We also show that transverse currents in the plasma ring are closed inside the magnetosphere forming the high latitude continuation of the ordinary ring current. The obtained results are used for the explanation of ring like form of the auroral oval. We also analyze the processes of the formation of multiscale auroral structures including thin auroral arcs and discuss the difficulties of the theories of alfvenic acceleration of auroral electrons.

  6. Observation of auroral secondary electrons in the Jovian magnetosphere

    NASA Technical Reports Server (NTRS)

    Mcnutt, Ralph L., Jr.; Bagenal, Fran; Thorne, Richard M.

    1990-01-01

    Localized enhancements in the flux of suprathermal electrons were observed by the Voyager 1 Plasma Science instrument near the outer boundary of the Io plasma torus between L = 7.5 and l = 10. This localization, which occurs within the general region of hot electrons noted by Sittler and Strobel (1987), and the spectral characteristics of the observed electrons are consistent with secondary (backscattered) electron production by intense Jovian auroral energetic particle precipitation and support the hypothesis that such electrons may contribute to the processes that heat the plasma in this region of the magnetosphere.

  7. E and F region study of the evening sector auroral oval - A Chatanika/Dynamics Explorer 2/NOAA 6 comparison

    NASA Technical Reports Server (NTRS)

    Senior, C.; Sharber, J. R.; Winningham, J. D.; De La Beaujardiere, O.; Heelis, R. A.; Evans, D. S.; Sugiura, M.; Hoegy, W. R.

    1987-01-01

    Simultaneous data from the Chatanika radar and the DE 2 and NOAA 6 satellites are used to study the typical behavior of the winter evening-sector auroral plasma during moderate and steady magnetic activity. The equatorward edge of the auroral E layer, of the region 2 field-aligned currents, and of the region of intense convection are colocated. The auroral E layer extends several degrees south of the equatorward edge of the keV electron precipitation from the CPS. Although the main trough and ionization channel are embedded in a region of intense electric field where the plasma flows sunward at high speed, the flux tubes associated with these two features have different time histories. The midlatitude trough is located south of the region of electron precipitation, above a proton aurora. The ionization channel marks the poleward edge of the main trough and is colocated with the equatorward boundary of the electron precipitation from the central plasma sheet.

  8. The Structure and Properties of 0.1 - 100 keV Electron Distributions Over Jupiter's Polar Aurora Region and their Contribution to Polar Aurora Emissions

    NASA Astrophysics Data System (ADS)

    Ebert, R. W.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Chae, K.; Connerney, J. E. P.; Clark, G. B.; Gladstone, R.; Hue, V.; Kurth, W. S.; Levin, S.; Louarn, P.; Mauk, B.; McComas, D. J.; Paranicas, C.; Saur, J.; Reno, C.; Szalay, J. R.; Thomsen, M. F.; Valek, P. W.; Weidner, S.; Wilson, R. J.

    2017-12-01

    In addition to the main emissions in the north and south, Jupiter's auroral emissions also include polar, satellite-related, and other features. Here we present observations from Juno's Jovian Auroral Distributions Experiment (JADE) of 0.1 - 100 keV electrons in Jupiter's polar aurora region during the spacecraft's northern and southern polar passes bounding PJ1 (27 August 2016), PJ3 (11 December 11 2016), PJ4 (2 February 2017), PJ5 (27 March 2017), PJ6 (19 May 2017), and PJ7 (11 July 2017). Specifically, we focus on the spatial structure, energy and pitch angle distributions, and energy flux and spectra of these electrons. The observations reveal regions containing magnetic field aligned beams of bi-directional electrons having broad energy distributions interspersed between beams of upward electrons with narrow, peaked energy distributions, regions void of these electrons, and regions dominated by penetrating radiation, with penetrating radiation being most common. The electrons show evidence of acceleration via parallel electric fields (inverted-V structures) and via stochastic processes (bi-directional distributions). The inverted-V structures identified to date were observed from 1.4 - 2.9 RJ and had spatial scales of 100s to 1000s of kilometers along Juno's trajectory. The upward energy flux of the electron distributions was typically greater than the downward energy flux and their contribution to producing Jupiter's polar aurora emissions will be discussed.

  9. Double structure of ionospheric conductivity in the midnight auroral oval during a substorm

    NASA Astrophysics Data System (ADS)

    Kotikov, A. L.; Shishkina, E. M.; Troshichev, O. A.; Sergienko, T. I.

    1995-02-01

    Measurements of precipitating particles on board Defense Meteorological Satellite Program (DMSP) F7 spacecraft are used to analyze the distribution of ionospheric conductance in the midnight auroral zone during substorms. The distribution is compared with the meridional profile of ionospheric currents calculated from magnetic data from the Kara meridional chain. Two regions of high Hall conductance are found; one of them is the traditional auroral zone, at latitudes 64-68 deg, and the other is a narrow band at latitudes 70-73 deg. The position of high conductance zones is in agreement with the location of the intense westward currents. The accelerated particle population is typical of electrons E(sub e) greater than 5 keV in the high conductance region.

  10. Retraction: Using the Medipix3 detector for direct electron imaging in the range 60 keV to 200 keV in electron microscopy Retraction: Using the Medipix3 detector for direct electron imaging in the range 60 keV to 200 keV in electron microscopy

    NASA Astrophysics Data System (ADS)

    Mir, J. A.; Plackett, R.; Shipsey, I.; dos Santos, J. M. F.

    2018-01-01

    The paper "Using the Medipix3 detector for direct electron imaging in the range 60keV to 200keV in electron microscopy" by J.A. Mir, R. Plackett, I. Shipsey and J.M.F. dos Santos has been retracted following the authors' request on the basis of the existence of a disagreement about the ownership of the data, to prevent conflict between collaborators.

  11. The Role of the Auroral Processes in the Formation of the Outer Electron Radiation Belt

    NASA Astrophysics Data System (ADS)

    Stepanova, M. V.; Antonova, E. E.; Pinto, V. A.; Moya, P. S.; Riazantseva, M.; Ovchinnikov, I.

    2016-12-01

    The role of the auroral processes in the formation of the outer electron radiation belt during storms is analyzed using the data of RBSP mission, low orbiting satellites and ground based observations. We analyze fluxes of the low energy precipitating ions using data of the Defense Meteorological Satellite Program (DMSP). The location of the auroral electrojet is obtained from the IMAGE magnetometer network, and of the electron distribution in the outer radiation belt from the RBSP mission. We take into account the latest results on the auroral oval mapping in accordance with which the most part of the auroral oval maps not to the plasma sheet. It maps into the surrounding the Earth plasma ring in which transverse currents are closed inside the magnetosphere. Such currents constitute the high latitude continuation of the ordinary ring current. The development of the ring current and its high latitude continuation generates strong distortion of the Earth's magnetic field and corresponding adiabatic variation of the relativistic electron fluxes. This adiabatic variation should be considered for the analysis of the processes of the acceleration of relativistic electrons and formation of the outer radiation belt. We also analyze the plasma pressure profiles during storms and demonstrate the formation of sharp plasma pressure peak at the equatorial boundary of the auroral oval. It is shown that the observed this peak is directly connected to the creation of the seed population of relativistic electrons. We discuss the possibility to predict the position of new radiation belt during recovery phase of the magnetic storm using data of low orbiting and ground based observations.

  12. Auroral and photoelectron fluxes in cometary ionospheres

    NASA Astrophysics Data System (ADS)

    Bhardwaj, A.; Haider, S. A.; Spinghal, R. P.

    1990-05-01

    The analytical yield spectrum method has been used to ascertain photoelectron and auroral electron fluxes in cometary ionospheres, with a view to determining the effects of cometocentric distances, solar zenith angle, and solar minimum and maximum conditions. Auroral electron fluxes are thus calculated for monoenergetic and observed primary electron spectra; auroral electrons are found to make a larger contribution to the observed electron spectrum than EUV-generated photoelectrons. Good agreement is established with extant theoretical works.

  13. Energy of auroral electrons and Z mode generation

    NASA Technical Reports Server (NTRS)

    Krauss-Varban, D.; Wong, H. K.

    1990-01-01

    The present consideration of Z-mode radiation generation, in light of observational results indicating that the O mode and second-harmonic X-mode emissions can prevail over the X-mode fundamental radiation when suprathermal electron energy is low, gives attention to whether the thermal effect on the Z-mode dispersion can be equally important, and whether the Z-mode can compete for the available free-energy source. It is found that, under suitable circumstances, the growth rate of the Z-mode can be substantial even for low suprathermal auroral electron energies. Growth is generally maximized for propagation perpendicular to the magnetic field.

  14. Anomalous auroral electron distributions due to an artificial ion beam in the ionosphere

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Arnoldy, R. L.; Kaufmann, R. L.; Cahill, L. J., Jr.; Kintner, P. M.; Walker, D. N.

    1982-01-01

    Results are reported for the perturbation of the auroral ionosphere by the operation of an ion gun which injected about 100 mA of 25-eV Ar(+) ions at upgoing pitch angles over a discrete auroral arc. The major effects observed were the excitation of intense broadband electric field fluctuations at zero-10 kHz, and the appearance of streaming and isotropic heating in different parts of superthermal electron velocity space. A scenario is explored in which electron runaway or streaming is expected between the trapping speed and the critical velocity for cyclotron interactions with the waves, where the streaming electrons carry the current that would be carried by thermals or energetic electrons in the absence of the waves. A current of about 1.0 microA/sq m is carried by the streaming electrons. The gun-associated electrons were anomalous in the sense that their anisotropy was the opposite of that observed in the natural aurora.

  15. The Jovian Auroral Distributions Experiment (JADE) on the Juno Mission to Jupiter

    NASA Astrophysics Data System (ADS)

    McComas, D. J.; Alexander, N.; Allegrini, F.; Bagenal, F.; Beebe, C.; Clark, G.; Crary, F.; Desai, M. I.; De Los Santos, A.; Demkee, D.; Dickinson, J.; Everett, D.; Finley, T.; Gribanova, A.; Hill, R.; Johnson, J.; Kofoed, C.; Loeffler, C.; Louarn, P.; Maple, M.; Mills, W.; Pollock, C.; Reno, M.; Rodriguez, B.; Rouzaud, J.; Santos-Costa, D.; Valek, P.; Weidner, S.; Wilson, P.; Wilson, R. J.; White, D.

    2017-11-01

    The Jovian Auroral Distributions Experiment (JADE) on Juno provides the critical in situ measurements of electrons and ions needed to understand the plasma energy particles and processes that fill the Jovian magnetosphere and ultimately produce its strong aurora. JADE is an instrument suite that includes three essentially identical electron sensors (JADE-Es), a single ion sensor (JADE-I), and a highly capable Electronics Box (EBox) that resides in the Juno Radiation Vault and provides all necessary control, low and high voltages, and computing support for the four sensors. The three JADE-Es are arrayed 120∘ apart around the Juno spacecraft to measure complete electron distributions from ˜0.1 to 100 keV and provide detailed electron pitch-angle distributions at a 1 s cadence, independent of spacecraft spin phase. JADE-I measures ions from ˜5 eV to ˜50 keV over an instantaneous field of view of 270∘×90∘ in 4 s and makes observations over all directions in space each 30 s rotation of the Juno spacecraft. JADE-I also provides ion composition measurements from 1 to 50 amu with m/Δ m˜2.5, which is sufficient to separate the heavy and light ions, as well as O+ vs S+, in the Jovian magnetosphere. All four sensors were extensively tested and calibrated in specialized facilities, ensuring excellent on-orbit observations at Jupiter. This paper documents the JADE design, construction, calibration, and planned science operations, data processing, and data products. Finally, the Appendix describes the Southwest Research Institute [SwRI] electron calibration facility, which was developed and used for all JADE-E calibrations. Collectively, JADE provides remarkably broad and detailed measurements of the Jovian auroral region and magnetospheric plasmas, which will surely revolutionize our understanding of these important and complex regions.

  16. Generation of auroral kilometric radiation and the structure of auroral acceleration region

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Kan, J. R.; Wu, C. S.

    1980-01-01

    Generation of auroral kilometric radiation (AKR) in the auroral acceleration region is studied. It is shown that auroral kilometric radiation can be generated by backscattered electrons trapped in the acceleration region via a cyclotron maser process. The parallel electric field in the acceleration region is required to be distributed over 1-2 earth radii. The observed AKR frequency spectrum can be used to estimate the altitude range of the auroral acceleration region. The altitudes of the lower and upper boundaries of the acceleration region determined from the AKR data are respectively approximately 2000 and 9000 km.

  17. Infrared Auroral Emissions Driven by Resonant Electron Impact Excitation of NO Molecules

    NASA Astrophysics Data System (ADS)

    Campbell, L.; Brunger, M. J.; Petrovic, Z. Lj.; Jelisavcic, M.; Panajotovic, R.; Buckman, S. J.

    2004-05-01

    Although only a minor constituent of the earth's upper atmosphere, nitric oxide (NO) plays a major role in infrared auroral emissions due to radiation from vibrationally excited (NO*) states. The main process leading to the production of these excited molecules was thought to be chemiluminescence, whereby excited nitrogen atoms interact with oxygen molecules to form vibrationally excited nitric oxide (NO*) and atomic oxygen. Here we show evidence that a different production mechanism for NO*, due to low energy electron impact excitation of NO molecules, is responsible for more than 30% of the NO auroral emission near 5 μm.

  18. Statistical Comparisons of Meso- and Small-Scale Field-Aligned Currents with Auroral Electron Acceleration Mechanisms from FAST Observations

    NASA Astrophysics Data System (ADS)

    Dombeck, J. P.; Cattell, C. A.; Prasad, N.; Sakher, A.; Hanson, E.; McFadden, J. P.; Strangeway, R. J.

    2016-12-01

    Field-aligned currents (FACs) provide a fundamental driver and means of Magnetosphere-Ionosphere (M-I) coupling. These currents need to be supported by local physics along the entire field line generally with quasi-static potential structures, but also supporting the time-evolution of the structures and currents, producing Alfvén waves and Alfvénic electron acceleration. In regions of upward current, precipitating auroral electrons are accelerated earthward. These processes can result in ion outflow, changes in ionospheric conductivity, and affect the particle distributions on the field line, affecting the M-I coupling processes supporting the individual FACs and potentially the entire FAC system. The FAST mission was well suited to study both the FACs and the electron auroral acceleration processes. We present the results of the comparisons between meso- and small-scale FACs determined from FAST using the method of Peria, et al., 2000, and our FAST auroral acceleration mechanism study when such identification is possible for the entire ˜13 year FAST mission. We also present the latest results of the electron energy (and number) flux ionospheric input based on acceleration mechanism (and FAC characteristics) from our FAST auroral acceleration mechanism study.

  19. Electron Velocity Shear Instability in the Auroral Ionosphere.

    DTIC Science & Technology

    1982-06-25

    function of order .1 ~e y Le’ L 0, Vde - - (ve /2ae) Xn n/ax, Z is the plasma dispersion function and Z’( ) = dZ/d . The ion response X is simply...and 2 current. systems in the auroral ionosphere [lijima and Potemra, 19761 and to electron current return current regions in solar flares [Knight and... SYSTEMS (OS) -TE IS CDP:ES) or.XCCS SYSTE.. ENGLNEERING ORG DIRECTOR WASHINGTON, D.C. 20305 DEFENSE NUCLEAR AGENCY OICY ATTN R. CRAWFORDi,.’, WASHINGTION

  20. Precipitating auroral electrons and lower thermospheric nitric oxide densities: SNOE, POLAR, SAMPEX, and NOAA/POES Comparisons for Geomagnetic Storms in 1998-2001

    NASA Astrophysics Data System (ADS)

    Baker, D. N.; Fisher, T. A.; Barth, C. A.; Mankoff, K. D.; Kanekal, S. G.; Bailey, S. M.; Petrinec, S. M.; Luhmann, J. G.; Mason, G. M.; Mazur, J. E.; Evans, D. S.

    2002-05-01

    Nitric oxide (NO) densities measured at altitudes between 97 and 150 km have been acquired using the UVS sensor onboard the Student Nitric Oxide Explorer (SNOE) spacecraft during the years 1998-2001. These data are compared with energetic electron fluxes (E>25 keV) measured concurrently using a sensitive sensor system (LICA) onboard the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) spacecraft. Geomagnetic storm intervals are examined to determine altitude and latitude variations of NO density as it compares to energetic electron precipitation. A broader statistical analysis is then carried out using daily averages of peak NO densities (at 106 km altitudes) and electron intensities measured by SAMPEX/LICA and by the TED sensor system onboard the NOAA/Polar Orbiting Environmental Satellite (POES) spacecraft. We also use the PIXIE instrument onboard POLAR to obtain global views of 2-12 keV x-rays emanating from the upper atmosphere. This gives a broad synoptic measure of relatively low-energy electron precipitation into the atmosphere. Latitude versus time displays of the UVS, PIXIE, LICA and TED data show excellent temporal and spatial correlations of the data sets. More detailed comparisons help us to assess spectral and local time relationships between auroral particle inputs and lower thermospheric chemical responses. These results are potentially quite important since past modeling has shown that particle inputs are significant for changing the chemistry and subsequent dynamics of the atmosphere.

  1. Relationships between particle precipitation and auroral forms

    NASA Technical Reports Server (NTRS)

    Burch, J. L.; Winningham, J. D.

    1978-01-01

    The paper discusses recent measurements pertaining to the relationship between high-latitude particle (electron) precipitation and auroras. The discussion covers three topics: the large-scale relationships between auroral forms and the particle populations of the magnetosphere as determined from satellite measurements; (2) the relationship between satellite and sounding-rocket observations, particularly field-aligned pitch-angle distributions and upward field-aligned currents measured in the vicinity of auroral forms; and (3) recent results on the interaction of auroral electrons with the atmosphere.

  2. Sources, properties, and energization of auroral particle precipitation

    NASA Astrophysics Data System (ADS)

    Wing, S.; Johnson, J.; Khazanov, G. V.

    2017-12-01

    The sources of and the physical processes associated with the auroral ion and electron precipitation are studied with DMSP satellites. The electron aurora has been previously classified into three categories: diffuse, monoenergetic, and broadband aurorae. The diffuse auroral electrons can be observed mainly in 22:00 - 09:00 MLT, which coincides much with the spatial distribution of the whistler-mode chorus waves that have been shown to be the predominant mechanism for pitch-angle scattering magnetospheric electrons into the loss cone, but there appears to be a separate population near noon, which may be associated with solar wind particles. The broadband auroral electrons can be found mostly at 22:00 - 02:00 MLT and pre-noon where Alfvén waves, which cause broadband electron acceleration, are observed in the magnetosphere. On the other hand, the monoenergetic auroral electrons can be observed at dusk-midnight sector, pre- and post-noon. The monoenergetic electrons have been previously thought as magnetospheric electrons that have gone through a quasi-static parallel electric field in the upward field-aligned current regions. However, there may be a connection between monoenergetic and broadband electrons in that the low frequency Alfvén wave-electron interaction can result in monoenergetic electron signature. This is consistent with the observations where broadband and monoenergetic electrons are often spatially co-located. Precipitating electrons can ionize the neutrals in the ionosphere, which can travel upward, which can precipitate in the opposite hemisphere or reflected back to the same hemisphere by upward field-aligned potential drop. Either way, the upward flowing electrons can greatly modify the initial precipitating electron population. Substorm processes increase the power of the diffuse, monoenergetic, and broadband electron aurora by 310%, 71%, and 170%, respectively. Substorms energize the ion aurora mainly in the 21:00-05:00 MLT sector. The

  3. Mirror instability and origin of morningside auroral structure

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Schulz, M.; Fennell, J. F.; Kishi, A. M.

    1983-01-01

    Auroral optical imagery shows marked differences between auroral features of the evening and morning sectors: the separation between diffuse and discrete auroras in the evening sector is not distinct in the morning sector, which is dominated by auroral patches and multiple banded structures aligned along some direction. Plasma distribution function signatures also show marked differences: downward electron beams and inverted-V signatures prefer the evening sector, while the electron spectra on the morning sector are similar to the diffuse aurora. A theory of morningside auroras consistent with these features was constructed. The theory is based on modulation of the growth rates of electron cyclotron waves by the mirror instability, which is in turn driven by inward-convected ions that have become anisotropic. This modulation produces alternating bands of enhanced and reduced electron precipitation which approximate the observed multiple auroral bands and patches of the morning sector.

  4. Exploring the Alfven-Wave Acceleration of Auroral Electrons in the Laboratory

    NASA Astrophysics Data System (ADS)

    Schroeder, James William Ryan

    Inertial Alfven waves occur in plasmas where the Alfven speed is greater than the electron thermal speed and the scale of wave field structure across the background magnetic field is comparable to the electron skin depth. Such waves have an electric field aligned with the background magnetic field that can accelerate electrons. It is likely that electrons are accelerated by inertial Alfven waves in the auroral magnetosphere and contribute to the generation of auroras. While rocket and satellite measurements show a high level of coincidence between inertial Alfven waves and auroral activity, definitive measurements of electrons being accelerated by inertial Alfven waves are lacking. Continued uncertainty stems from the difficulty of making a conclusive interpretation of measurements from spacecraft flying through a complex and transient process. A laboratory experiment can avoid some of the ambiguity contained in spacecraft measurements. Experiments have been performed in the Large Plasma Device (LAPD) at UCLA. Inertial Alfven waves were produced while simultaneously measuring the suprathermal tails of the electron distribution function. Measurements of the distribution function use resonant absorption of whistler mode waves. During a burst of inertial Alfven waves, the measured portion of the distribution function oscillates at the Alfven wave frequency. The phase space response of the electrons is well-described by a linear solution to the Boltzmann equation. Experiments have been repeated using electrostatic and inductive Alfven wave antennas. The oscillation of the distribution function is described by a purely Alfvenic model when the Alfven wave is produced by the inductive antenna. However, when the electrostatic antenna is used, measured oscillations of the distribution function are described by a model combining Alfvenic and non-Alfvenic effects. Indications of a nonlinear interaction between electrons and inertial Alfven waves are present in recent data.

  5. CINEMA (Cubesat for Ion, Neutral, Electron, MAgnetic fields)

    NASA Astrophysics Data System (ADS)

    Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Wang, L.; Sample, J. G.; Horbury, T. S.; Roelof, E. C.; Lee, D.; Seon, J.; Hines, J.; Vo, H.; Tindall, C.; Ho, J.; Lee, J.; Kim, K.

    2009-12-01

    The NSF-funded CINEMA mission will provide cutting-edge magnetospheric science and critical space weather measurements, including high sensitivity mapping and high cadence movies of ring current, >4 keV Energetic Neutral Atom (ENA), as well as in situ measurements of suprathermal electrons (>~2 keV) and ions (>~ 4 keV) in the auroral and ring current precipitation regions, all with ~1 keV FWHM resolution and uniform response up to ~100 keV. A Suprathermal Electron, Ion, Neutral (STEIN) instrument adds an electrostatic deflection system to the STEREO STE (SupraThermal Electron) 4-pixel silicon semiconductor sensor to separate ions from electrons and from ENAs up to ~20 keV. In addition, inboard and outboard (on an extendable 1m boom) magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. A new attitude control system (ACS) uses torque coils, a solar aspect sensor and the magnetometers to de-tumble the 3u CINEMA spacecraft, then spin it up to ~1 rpm with the spin axis perpendicular to the ecliptic, so STEIN can sweep across most of the sky every minute. Ideally, CINEMA will be placed into a high inclination low earth orbit that crosses the auroral zone and cusp. An S-band transmitter will be used to provide > ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station. Two more identical CINEMA spacecraft will be built by Kyung Hee University (KHU) in Korea under their World Class University (WCU) program, to provide stereo ENA imaging and multi-point in situ measurements. Furthermore, CINEMA’s development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft will be important for future nanosatellite space missions.

  6. Diffusive transport of several hundred keV electrons in the Earth's slot region

    NASA Astrophysics Data System (ADS)

    Ma, Q.; Li, W.; Thorne, R. M.; Bortnik, J.

    2017-12-01

    We investigate the gradual diffusion of energetic electrons from the inner edge of the outer radiation belt into the slot region. The Van Allen Probes observed slow inward diffusion and decay of 200-600 keV electrons following the intense geomagnetic storm that occurred on 17 March 2013. During the 10-day non-disturbed period following the storm, the peak of electron fluxes gradually moved from L 2.7 to L 2.4, and the flux levels decreased by a factor of 2-4 depending on the electron energy. We simulated the radial intrusion and decay of electrons using a 3-dimentional diffusion code, which reproduced the energy-dependent transport of electrons from 100 keV to 1 MeV in the slot region. At energies of 100-200 keV, the electrons experience fast transport across the slot region due to the dominance of radial diffusion; at energies of 200-600 keV, the electrons gradually diffuse and decay in the slot region due to the comparable radial diffusion rate and pitch angle scattering rate by plasmaspheric hiss; at energies of E > 700 keV, the electrons stopped diffusing near the inner edge of outer radiation belt due to the dominant pitch angle scattering loss. In addition to plasmaspheric hiss, magnetosonic waves and VLF waves can cause the loss of high pitch angle electrons, relaxing the sharp `top-hat' shaped pitch angle distributions created by plasmaspheric hiss. Our simulation indicates the importance of radial diffusion and pitch angle scattering in forming the diffusive intrusion of energetic electrons across the slot region.

  7. Studies of auroral X-ray imaging from high altitude spacecraft

    NASA Technical Reports Server (NTRS)

    Mckenzie, D. L.; Mizera, P. F.; Rice, C. J.

    1980-01-01

    Results of a study of techniques for imaging the aurora from a high altitude satellite at X-ray wavelengths are summarized. The X-ray observations allow the straightforward derivation of the primary auroral X-ray spectrum and can be made at all local times, day and night. Five candidate imaging systems are identified: X-ray telescope, multiple pinhole camera, coded aperture, rastered collimator, and imaging collimator. Examples of each are specified, subject to common weight and size limits which allow them to be intercompared. The imaging ability of each system is tested using a wide variety of sample spectra which are based on previous satellite observations. The study shows that the pinhole camera and coded aperture are both good auroral imaging systems. The two collimated detectors are significantly less sensitive. The X-ray telescope provides better image quality than the other systems in almost all cases, but a limitation to energies below about 4 keV prevents this system from providing the spectra data essential to deriving electron spectra, energy input to the atmosphere, and atmospheric densities and conductivities. The orbit selection requires a tradeoff between spatial resolution and duty cycle.

  8. Venus nightside ionosphere - A model with KeV electron impact ionization

    NASA Technical Reports Server (NTRS)

    Kumar, S.

    1982-01-01

    The impact of keV electrons is proposed as the strongest source of ionization in a full-up Venus nightside ionosphere model for the equatorial midnight region. The electron impacts lead to a peak ion density of 100,000/cu cm, which was observed by the PV-OIMS experiment on several occasions. In addition, the observed altitude profiles of CO2(+), O(+), O2(+), H(+), and H2(+) can be reproduced by the model on condition that the available keV electron flux is approximated by a reasonable extrapolation from fluxes observed at lower energies.

  9. Modelling of auroral electrodynamical processes: Magnetosphere to mesosphere

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Gorney, D. J.; Kishi, A. M.; Newman, A. L.; Schulz, M.; Walterscheid, R. L.; CORNWALL; Prasad, S. S.

    1982-01-01

    Research conducted on auroral electrodynamic coupling between the magnetosphere and ionosphere-atmosphere in support of the development of a global scale kinetic plasma theory is reviewed. Topics covered include electric potential structure in the evening sector; morning and dayside auroras; auroral plasma formation; electrodynamic coupling with the thermosphere; and auroral electron interaction with the atmosphere.

  10. Auroral photometry from the atmosphere Explorer satellite

    NASA Technical Reports Server (NTRS)

    Rees, M. H.; Abreu, V. J.

    1984-01-01

    Attention is given to the ability of remote sensing from space to yield quantitative auroral and ionospheric parametrers, in view of the auroral measurements made during two passes of the Explorer C satellite over the Poker Flat Optical Observatory and the Chatanika Radar Facility. The emission rate of the N2(+) 4278 A band computed from intensity measurements of energetic auroral electrons has tracked the same spetral feature that was measured remotely from the satellite over two decades of intensity, providing a stringent test for the measurement of atmospheric scattering effects. It also verifies the absolute intensity with respect to ground-based photometric measurements. In situ satellite measurments of ion densities and ground based electron density profile radar measurements provide a consistent picture of the ionospheric response to auroral input, while also predicting the observed optical emission rate.

  11. Microsecond Electron Beam Source with Electron Energy Up to 400 Kev and Plasma Anode

    NASA Astrophysics Data System (ADS)

    Abdullin, É. N.; Basov, G. F.; Shershnev, S.

    2017-12-01

    A new high-power source of electrons with plasma anode for producing high-current microsecond electron beams with electron energy up to 400 keV has been developed, manufactured, and put in operation. To increase the cross section and pulse current duration of the beam, a multipoint explosive emission cathode is used in the electron beam source, and the beam is formed in an applied external guiding magnetic field. The Marx generator with vacuum insulation is used as a high-voltage source. Electron beams with electron energy up to 300-400 keV, current of 5-15 kA, duration of 1.5-3 μs, energy up to 4 kJ, and cross section up to 150 cm2 have been produced. The operating modes of the electron beam source are realized in which the applied voltage is influenced weakly on the current. The possibility of source application for melting of metal surfaces is demonstrated.

  12. Diffusive Transport of Several Hundred keV Electrons in the Earth's Slot Region

    NASA Astrophysics Data System (ADS)

    Ma, Q.; Li, W.; Thorne, R. M.; Bortnik, J.; Reeves, G. D.; Spence, H. E.; Turner, D. L.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Baker, D. N.

    2017-10-01

    We investigate the gradual diffusion of energetic electrons from the inner edge of the outer radiation belt into the slot region. The Van Allen Probes observed slow inward diffusion and decay of 200-600 keV electrons following the intense geomagnetic storm that occurred on 17 March 2013. During the 10 day nondisturbed period following the storm, the peak of electron fluxes gradually moved from L 2.7 to L 2.4, and the flux levels decreased by a factor of 2-4 depending on the electron energy. We simulated the radial intrusion and decay of electrons using a three-dimensional diffusion code, which reproduced the energy-dependent transport of electrons from 100 keV to 1 MeV in the slot region. At energies of 100-200 keV, the electrons experience fast transport across the slot region due to the dominance of radial diffusion; at energies of 200-600 keV, the electrons gradually diffuse and decay in the slot region due to the comparable rate of radial diffusion and pitch angle scattering by plasmaspheric hiss; at energies of E > 700 keV, the electrons stopped diffusing near the inner edge of outer radiation belt due to the dominant pitch angle scattering loss. In addition to plasmaspheric hiss, magnetosonic waves and VLF transmitters can cause the loss of high pitch angle electrons, relaxing the sharp "top-hat" shaped pitch angle distributions created by plasmaspheric hiss. Our simulation indicates the importance of balance between radial diffusion and loss through pitch angle scattering in forming the diffusive intrusion of energetic electrons across the slot region.

  13. Diffusive Transport of Several Hundred keV Electrons in the Earth's Slot Region

    DOE PAGES

    Ma, Q.; Li, W.; Thorne, R. M.; ...

    2017-09-29

    Here, we investigate the gradual diffusion of energetic electrons from the inner edge of the outer radiation belt into the slot region. The Van Allen Probes observed slow inward diffusion and decay of ~200–600 keV electrons following the intense geomagnetic storm that occurred on 17 March 2013. During the 10 day nondisturbed period following the storm, the peak of electron fluxes gradually moved from L ~ 2.7 to L ~ 2.4, and the flux levels decreased by a factor of ~2–4 depending on the electron energy. We simulated the radial intrusion and decay of electrons using a three–dimensional diffusion code,more » which reproduced the energy–dependent transport of electrons from ~100 keV to 1 MeV in the slot region. At energies of 100–200 keV, the electrons experience fast transport across the slot region due to the dominance of radial diffusion; at energies of 200–600 keV, the electrons gradually diffuse and decay in the slot region due to the comparable rate of radial diffusion and pitch angle scattering by plasmaspheric hiss; at energies of E > 700 keV, the electrons stopped diffusing near the inner edge of outer radiation belt due to the dominant pitch angle scattering loss. In addition to plasmaspheric hiss, magnetosonic waves and VLF transmitters can cause the loss of high pitch angle electrons, relaxing the sharp “top–hat” shaped pitch angle distributions created by plasmaspheric hiss. Our simulation indicates the importance of balance between radial diffusion and loss through pitch angle scattering in forming the diffusive intrusion of energetic electrons across the slot region.« less

  14. The Strongest 40 keV Electron Acceleration By ICME-driven Shocks At 1 AU

    NASA Astrophysics Data System (ADS)

    Yang, L.; Wang, L.; Li, G.; Wimmer-Schweingruber, R. F.; He, J.; Tu, C. Y.; Bale, S. D.

    2017-12-01

    Here we present a comprehensive case study of the in situ electron acceleration at the two ICME-driven shocks observed by WIND/3DP on February 11, 2000 and July 22, 2004. For the 11 February 2000 shock (the 22 July 2004 shock), the shocked electrons in the downstream show significant flux enhancements over the ambient solar wind electrons at energies up to 40 keV (66 keV) with a 6.0 times (1.9 times) ehancment at 40 keV, the strongest among all the quasi-perpendicular (quasi-parallel) ICME-driven shocks observed by the WIND spacecraft at 1 AU from 1995 through 2014. We find that in both shocks, the shocked electron fluxes at 0.5-40 keV fit well to a double power-law spectrum, J ˜ E-β, bending up at ˜2 keV. In the downstream, these shocked electrons show stronger fluxes in the anti-sunward direction, but their enhancement over the ambient fluxes peaks near 90° pitch angle (PA). For the 11 February 2000 shock, the electron spectral index, β, appears to not vary with the electron PA, while for the 22 July 2004 shock, β roughly decreases from the anti-sunward PA direction to the sunward PA direction. All of these spectral indexes are strongly larger than the theoretical prediction of diffusive shock acceleration. At energies above (below) 2 keV, however, the shocked electron β is similar to the solar wind superhalo (halo) electrons observed at quiet times. These results suggest that the electron acceleration at the ICME-driven shocks at 1 AU may favor the shock drift acceleration, and the superthermal electrons accelerated by the interplanetary shocks may contribute to the formation of the halo and superhalo electron populations in the solar wind.

  15. Electromagnetic plasma wave emissions from the auroral field lines

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1977-01-01

    The most important types of auroral radio emissions are reviewed, both from a historical perspective as well as considering the latest results. Particular emphasis is placed on four types of electromagnetic emissions which are directly associated with the plasma on the auroral field lines. These emissions are (1) auroral hiss, (2) saucers, (3) ELF noise bands, and (4) auroral kilometric radiation. Ray tracing and radio direction finding measurements indicate that both the auroral hiss and auroral kilometric radiation are generated along the auroral field lines relatively close to the earth, at radial distances from about 2.5 to 5 R sub e. For the auroral hiss the favored mechanism appears to be amplified Cerenkov radiation. For the auroral kilometric radiation several mechanisms have been proposed, usually involving the intermediate generation of electrostatic waves by the precipitating electrons.

  16. Superthermal (0.5- 100 keV) Electrons near the ICME-driven shocks

    NASA Astrophysics Data System (ADS)

    Yang, L.; Wang, L.; Li, G.; Tao, J.; He, J.; Tu, C.

    2016-12-01

    We present a survey of the 0.5 - 100 keV electrons associated with ICME-driven shocks at 1 AU, using the WIND/3DP electron measurements from 1995 to 2014. We select 66 good ICME-driven shocks, and use the "Rankine-Hugoniot" shock fitting technique to obtain the shock normal, shock velocity Vs, shock compression ratio r and magnetosonic Mach number Ms. We average the electron data in the 1-hour interval immediately after the shock front to obtain the sheath electron fluxes and in the 4-hour quiet-time interval before the shock to obtain the pre-event electron fluxes. Then we subtract the pre-event electron fluxes from the sheath electron fluxes to obtain the enhanced electron fluxes at the shock. We find that the enhanced electron fluxes are positively correlated with Vs and Ms, and generally fit well to a double power-law spectrum, J E-β. At 0.5 - 2 keV, the fitted spectral index β1 ranges from 2.1 to 5.9, negatively correlated with r and Ms. At 2 - 100 keV, the fitted index β2 is smaller than β1, with values ( 1.9 to 3.4) similar to the spectral indexes of quiet-time superhalo electrons in the solar wind. β2 shows no obvious correlation with r and Ms. Neither of β1 or β2 is in agreement with the diffusive shock theoretical predication. These results suggest that electron acceleration by interplanetary shocks may be more significant at a few keVs and the interplanetary shock acceleration can contribute to the production of solar wind superhalo electrons. However, a revision of the diffusive shock acceleration theory would be needed for the electron acceleration.

  17. Lyman alpha line shapes from electron impact H2 dissociative processes in the Jovian auroral zone

    NASA Technical Reports Server (NTRS)

    Waite, J. H., Jr.; Gladstone, G. R.

    1992-01-01

    Over the past two years several Lyman alpha line profile spectra of Jupiter were obtained using the International Ultraviolet Explorer (IUE) telescope. Several different regions of the planet were observed including the auroral zone, the low and mid latitudes, and the equatorial region which includes the Lyman alpha bulge region. These results have presented a very interesting picture of atomic hydrogen on Jupiter with explanations that range from ion outflow in the auroral zone to large thermospheric winds at low and mid latitudes. New data are needed to address the outstanding questions. Almost certainly, high resolution spectra from the Hubble Space Telescope will play a role in new observations. Better data also require better models, and better models require new laboratory data as inputs. The purpose of this program is two-fold: (1) to introduce a method by which new laboratory electron impact measurements of H2 dissociation can be used to calculate both the slow and fast H(S-2) and H(P-2) fragments in an H2 atmosphere; and (2) to determine the predicted Lyman alpha line shape that would result from electron impact production of these dissociative fragments in the Jovian auroral zone.

  18. The spatial-temporal ambiguity in auroral modeling

    NASA Technical Reports Server (NTRS)

    Rees, M. H.; Roble, R. G.; Kopp, J.; Abreu, V. J.; Rusch, D. W.; Brace, L. H.; Brinton, H. C.; Hoffman, R. A.; Heelis, R. A.; Kayser, D. C.

    1980-01-01

    The paper examines the time-dependent models of the aurora which show that various ionospheric parameters respond to the onset of auroral ionization with different time histories. A pass of the Atmosphere Explorer C satellite over Poker Flat, Alaska, and ground based photometric and photographic observations have been used to resolve the time-space ambiguity of a specific auroral event. The density of the O(+), NO(+), O2(+), and N2(+) ions, the electron density, and the electron temperature observed at 280 km altitude in a 50 km wide segment of an auroral arc are predicted by the model if particle precipitation into the region commenced about 11 min prior to the overpass.

  19. Magnetosphere - ionosphere coupling process in the auroral region estimated from auroral tomography

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Ogawa, Y.; Kadokura, A.; Gustavsson, B.; Kauristie, K.; Whiter, D. K.; Enell, C. F. T.; Brandstrom, U.; Sergienko, T.; Partamies, N.; Kozlovsky, A.; Miyaoka, H.; Kosch, M. J.

    2016-12-01

    We have studied the magnetosphere - ionosphere coupling process by using multiple auroral images and the ionospheric data obtained by a campaign observation with multi-point imagers and the EISCAT UHF radar in Northern Europe. We observed wavy structure of discrete arcs around the magnetic zenith at Tromso, Norway, from 22:00 to 23:15 UT on March 14, 2015, followed by auroral breakup, poleward expansion, and pulsating auroras. During this interval, the monochromatic (427.8nm) images were taken at a sampling interval of 2 seconds by three EMCCD imagers and at an interval of 10 seconds by totally six imagers. The EISCAT UHF radar at Tromso measured the ionospheric parameters along the magnetic field line from 20 to 24 UT. We applied the tomographic inversion technique to these data set to retrieve 3D distribution of the 427.8nm emission, that enabled us to obtain the following quantities for the auroras that change from moment to moment; (1) the relation between the 427.8nm emission and the electron density enhancement along the field line, (2) the horizontal distribution of energy flux of auroral precipitating electrons, and (3) the horizontal distribution of height-integrated ionospheric conductivity. By combining those with the ionospheric equivalent current estimated from the ground-based magnetometer network, we discuss the current system of a sequence of the auroral event in terms of the magnetosphere-ionosphere coupling.

  20. Characteristics of ionospheric electron density profiles in the auroral and polar cap regions from long-term incoherent scatter radar observations

    NASA Astrophysics Data System (ADS)

    Jee, G.; Kim, E.; Kwak, Y. S.; Kim, Y.; Kil, H.

    2017-12-01

    We investigate the climatological characteristics of the ionospheric electron density profiles in the auroral and polar cap regions in comparison with the mid-latitude ionosphere using incoherent scatter radars (ISR) observations from Svalbard (78.15N, 16.05E), Tromso (69.59N, 19.23E), and Millstone Hill (42.6N, 288.5E) during a period of 1995 - 2015. Diurnal variations of electron density profiles from 100 to 500 km are compared among the three radar observations during equinox, summer and winter solstice for different solar and geomagnetic activities. Also investigated are the physical characteristics of E-region and F-region peak parameters of electron density profiles in the auroral and polar cap regions, which are significantly different from the mid-latitude ionosphere. In the polar ionosphere, the diurnal variations of density profiles are extremely small in summer hemisphere. Semiannual anomaly hardly appears for all latitudes, but winter anomaly occurs at mid-latitude and auroral ionospheres for high solar activity. Nighttime density becomes larger than daytime density in the winter polar cap ionosphere for high solar activity. The E-region peak is very distinctive in the nighttime auroral region and the peak height is nearly constant at about 110 km for all conditions. Compared with the F-region peak density, the E-region peak density does not change much with solar activity. Furthermore, the E-region peak density can be even larger than F-region density for low solar activity in the auroral region, particularly during disturbed condition.

  1. The Strongest Acceleration of >40 keV Electrons by ICME-driven Shocks at 1 au

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Wang, Linghua; Li, Gang; Wimmer-Schweingruber, Robert F.; He, Jiansen; Tu, Chuanyi; Tian, Hui; Bale, Stuart D.

    2018-01-01

    We present two case studies of the in-situ electron acceleration during the 2000 February 11 shock and the 2004 July 22 shock, with the strongest electron flux enhancement at 40 keV across the shock, among all the quasi-perpendicular and quasi-parallel ICME-driven shocks observed by the WIND 3DP instrument from 1995 through 2014 at 1 au. We find that for this quasi-perpendicular (quasi-parallel) shock on 2000 February 11 (2004 July 22), the shocked electron differential fluxes at ∼0.4–50 keV in the downstream generally fit well to a double-power-law spectrum, J ∼ E ‑β , with an index of β ∼ 3.15 (4.0) at energies below a break at ∼3 keV (∼1 keV) and β ∼ 2.65 (2.6) at energies above. For both shock events, the downstream electron spectral indices appear to be similar for all pitch angles, which are significantly larger than the index prediction by diffusive shock acceleration. In addition, the downstream electron pitch-angle distributions show the anisotropic beams in the anti-sunward-traveling direction, while the ratio of the downstream over ambient fluxes appears to peak near 90° pitch angles, at all energies of ∼0.4–50 keV. These results suggest that in both shocks, shock drift acceleration likely plays an important role in accelerating electrons in situ at 1 au. Such ICME-driven shocks could contribute to the formation of solar wind halo electrons at energies ≲2 keV, as well as the production of solar wind superhalo electrons at energies ≳2 keV in interplanetary space.

  2. Charge dynamics of MgO single crystals subjected to KeV electron irradiation

    NASA Astrophysics Data System (ADS)

    Boughariou, A.; Blaise, G.; Braga, D.; Kallel, A.

    2004-04-01

    A scanning electron microscope has been equipped to study the fundamental aspects of charge trapping in insulating materials, by measuring the secondary electron emission (SEE) yield σ with a high precision (a few percent), as a function of energy, electron current density, and dose. The intrinsic secondary electron emission yield σ0 of uncharged MgO single crystals annealed at 1000 °C, 2 h, has been studied at four energies 1.1, 5, 15, and 30 keV on three different crystal orientations (100), (110), and (111). At low energies (1.1 and 5 keV) σ0 depends on the crystalline orientation wheras at high energies (30 keV) no differentiation occurs. It is shown that the value of the second crossover energy E2, for which the intrinsic SEE yield σ0=1, is extremely delicate to measure with precision. It is about 15 keV±500 eV for the (100) orientation, 13.5 keV±500 eV for the (110), and 18.5 keV±500 eV for the (111) one. At low current density J⩽105 pA/cm2, the variation of σ with the injected dose makes possible the observation of a self-regulated regime characterized by a steady value of the SEE yield σst=1. At low energies 1.1 and 5 keV, there is no current density effects in MgO, but at high energies ≈30 keV, apparent current density effects come from a bad collect of secondary electrons, due to very high negative surface potential. At 30 keV energy, an intense erratic electron exoemission was observed on the MgO (110) orientation annealed at 1500 °C. This phenomenon is the result of a disruptive process similar to flashover, which takes place at the surface of the material.

  3. Electron impact contribution to infrared NO emissions in auroral conditions

    NASA Astrophysics Data System (ADS)

    Campbell, L.; Brunger, M. J.

    2007-11-01

    Infrared emissions from nitric oxide, other than nightglow, are observed in aurora, principally due to a chemiluminescent reaction between excited nitrogen atoms and oxygen molecules that produces vibrationally excited NO. The rates for this chemiluminescent reaction have recently been revised. Based on new measurements of electron impact vibrational excitation of NO, it has been suggested that electron impact may also be significant in producing auroral NO emissions. We show results of a detailed calculation which predicts the infrared spectrum observed in rocket measurements, using the revised chemiluminescent rates and including electron impact excitation. For emissions from the second vibrational level and above, the shape of the spectrum can be reproduced within the statistical errors of the analysis of the measurements, although there is an unexplained discrepancy in the absolute value of the emissions. The inclusion of electron impact improves the agreement of the shape of the predicted spectrum with the measurements by accounting for part of the previously unexplained peak in emissions from the first vibrational level.

  4. Preliminary measurements of auroral energy deposition and middle atmosphere electrodynamic response during MAC/Epsilon

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.

    1989-01-01

    On the nights of October 21 and 28, 1987 (UT), two Nike Orion payloads (NASA 31.066 and 31.067) were launched from Andoya, Norway, as part of the MAC/Epsilon campaign, to study auroral energetics and their effect on the middle atmosphere. Each payload carried instrumentation to measure relativistic electrons from 0.1 to 1.0 MeV in 12 differential channels, and Bremsstrahlung X-rays from greater than 5 to greater than 80 KeV in 5 integral channels. In addition, instrumentation to measure ion densities and electric fields were also included on these and, in the case of 31.066, on other near simultaneous payloads. The first flight, 31.066, was launched under pre-magnetic midnight conditions during relatively stable auroral conditions. Flight 31.067 was launched during post-breakup conditions at which time pulsations of approx. 100 seconds duration were evident. The measured radiations including their spectral characteristics are compared for these two events, to appraise their effect on the electrodynamic properties of the middle atmosphere as determined by other rocket-borne measurements.

  5. Effect of excess superthermal hot electrons on finite amplitude ion-acoustic solitons and supersolitons in a magnetized auroral plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rufai, O. R., E-mail: rrufai@csir.co.za; Bharuthram, R., E-mail: rbharuthram@uwc.ac.za; Singh, S. V., E-mail: satyavir@iigs.iigm.res.in

    2015-10-15

    The effect of excess superthermal electrons is investigated on finite amplitude nonlinear ion-acoustic waves in a magnetized auroral plasma. The plasma model consists of a cold ion fluid, Boltzmann distribution of cool electrons, and kappa distributed hot electron species. The model predicts the evolution of negative potential solitons and supersolitons at subsonic Mach numbers region, whereas, in the case of Cairn's nonthermal distribution model for the hot electron species studied earlier, they can exist both in the subsonic and supersonic Mach number regimes. For the dayside auroral parameters, the model generates the super-acoustic electric field amplitude, speed, width, and pulsemore » duration of about 18 mV/m, 25.4 km/s, 663 m, and 26 ms, respectively, which is in the range of the Viking spacecraft measurements.« less

  6. Statistical study of auroral omega bands

    NASA Astrophysics Data System (ADS)

    Partamies, Noora; Weygand, James M.; Juusola, Liisa

    2017-09-01

    The presence of very few statistical studies on auroral omega bands motivated us to test-use a semi-automatic method for identifying large-scale undulations of the diffuse aurora boundary and to investigate their occurrence. Five identical all-sky cameras with overlapping fields of view provided data for 438 auroral omega-like structures over Fennoscandian Lapland from 1996 to 2007. The results from this set of omega band events agree remarkably well with previous observations of omega band occurrence in magnetic local time (MLT), lifetime, location between the region 1 and 2 field-aligned currents, as well as current density estimates. The average peak emission height of omega forms corresponds to the estimated precipitation energies of a few keV, which experienced no significant change during the events. Analysis of both local and global magnetic indices demonstrates that omega bands are observed during substorm expansion and recovery phases that are more intense than average substorm expansion and recovery phases in the same region. The omega occurrence with respect to the substorm expansion and recovery phases is in a very good agreement with an earlier observed distribution of fast earthward flows in the plasma sheet during expansion and recovery phases. These findings support the theory that omegas are produced by fast earthward flows and auroral streamers, despite the rarity of good conjugate observations.

  7. Generation of Z mode radiation by diffuse auroral electron precipitation

    NASA Astrophysics Data System (ADS)

    Dusenbery, P. B.; Lyons, L. R.

    1985-03-01

    The generation of Z mode waves by diffuse auroral electron precipitation is investigated assuming that a loss cone exists in the upgoing portion of the distribution due to electron interactions with the atmosphere. The waves are generated at frequencies above, but very near, the local electron cyclotron frequency omega(e) and at wave normal angles larger than 90 deg. In agreement with Hewitt et al. (1983), the group velocity is directed downward in regions where the ratio of the upper hybrid frequency omega(pe) to Omega(e) is less than 0.5, so that Z mode waves excited above a satellite propagate toward it and away from the upper hybrid resonance. Z mode waves are excited in a frequency band between Omega(e) and about 1.02 Omega(e), and with maximum growth rates of about 0.001 Omega(e). The amplification length is about 100 km, which allows Z mode waves to grow to the intensities observed by high-altitude satellites.

  8. Generation of Z mode radiation by diffuse auroral electron precipitation

    NASA Technical Reports Server (NTRS)

    Dusenbery, P. B.; Lyons, L. R.

    1985-01-01

    The generation of Z mode waves by diffuse auroral electron precipitation is investigated assuming that a loss cone exists in the upgoing portion of the distribution due to electron interactions with the atmosphere. The waves are generated at frequencies above, but very near, the local electron cyclotron frequency omega(e) and at wave normal angles larger than 90 deg. In agreement with Hewitt et al. (1983), the group velocity is directed downward in regions where the ratio of the upper hybrid frequency omega(pe) to Omega(e) is less than 0.5, so that Z mode waves excited above a satellite propagate toward it and away from the upper hybrid resonance. Z mode waves are excited in a frequency band between Omega(e) and about 1.02 Omega(e), and with maximum growth rates of about 0.001 Omega(e). The amplification length is about 100 km, which allows Z mode waves to grow to the intensities observed by high-altitude satellites.

  9. A statistical study of the THEMIS satellite data for plasma sheet electrons carrying auroral upward field-aligned currents

    NASA Astrophysics Data System (ADS)

    Lee, S.; Shiokawa, K.; McFadden, J. P.

    2010-12-01

    The magnetospheric electron precipitation along the upward field-aligned currents without the potential difference causes diffuse aurora, and the magnetospheric electrons accelerated by a field-aligned potential difference cause the intense and bright type of aurora, namely discrete aurora. In this study, we are trying to find out when and where the aurora can be caused with or without electron acceleration. We statistically investigate electron density, temperature, thermal current, and conductivity in the plasma sheet using the data from the electrostatic analyzer (ESA) onboard the THEMIS-D satellite launched in 2007. According to Knight (Planet. Space Sci., 1973) and Lyons (JGR, 1980), the thermal current, jth(∝ nT^(1/2) where n is electron density and T is electron temperature in the plasma sheet), represents the upper limit to field aligned current that can be carried by magnetospheric electrons without field-aligned potential difference. The conductivity, K(∝ nT^(-1/2)), represents the efficiency of the upward field-aligned current (j) that the field-aligned potential difference (V) can produce (j=KV). Therefore, estimating jth and K in the plasma sheet is important in understanding the ability of plasma sheet electrons to carry the field-aligned current which is driven by various magnetospheric processes such as flow shear and azimuthal pressure gradient. Similar study was done by Shiokawa et al. (2000) based on the auroral electron data obtained by the DMSP satellites above the auroral oval and the AMPTE/IRM satellite in the near Earth plasma sheet at 10-18 Re on February-June 1985 and March-June 1986 during the solar minimum. The purpose of our study is to examine auroral electrons with pitch angle information inside 12 Re where Shiokawa et al. (2000) did not investigate well. For preliminary result, we found that in the dawn side inner magnetosphere (source of the region 2 current), electrons can make sufficient thermal current without field

  10. Electron ionization of metastable nitrogen and oxygen atoms in relation to the auroral emissions

    NASA Astrophysics Data System (ADS)

    Pandya, Siddharth; Joshipura, K. N.

    Atomic and molecular excited metastable states (EMS) are exotic systems due to their special properties like long radiative life-time, large size (average radius) and large polarizability along with relatively smaller first ionization energy compared to their respective ground states (GS). The present work includes our theoretical calculations on electron impact ionization of metastable atomic states N( (2) P), N( (2) D) of nitrogen and O( (1) S), O( (1) D) of oxygen. The targets of our present interest, are found to be present in our Earth's ionosphere and they play an important role in auroral emissions observed in Earth’s auroral regions [1] as also in the emissions observed from cometary coma [2, 3] and airglow emissions. In particular, atomic oxygen in EMS can radiate, the visible O( (1) D -> (3) P) doublet 6300 - 6364 Å red doublet, the O( (1) S -> (1) D) 5577 Å green line, and the ultraviolet O( (1) S -> (3) P) 2972 Å line. For metastable atomic nitrogen one observes the similar emissions, in different wavelengths, from (2) D and (2) P states. At the Earth's auroral altitudes, from where these emissions take place in the ionosphere, energetic electrons are also present. In particular, if the metastable N as well as O atoms are ionized by the impact of electrons then these species are no longer available for emissions. This is a possible loss mechanism, and hence it is necessary to analyze the importance of electron ionization of the EMS of atomic O and N, by calculating the relevant cross sections. In the present paper we investigate electron ionization of the said metastable species by calculating relevant total cross sections. Our quantum mechanical calculations are based on projected approximate ionization contribution in the total inelastic cross sections [4]. Detailed results and discussion along with the significance of these calculations will be presented during the COSPAR-2014. References [1] A.Bhardwaj, and G. R. Gladstone, Rev. Geophys., 38

  11. SM91: Observations of interchange between acceleration and thermalization processes in auroral electrons

    NASA Technical Reports Server (NTRS)

    Pongratz, M.

    1972-01-01

    Results from a Nike-Tomahawk sounding rocket flight launched from Fort Churchill are presented. The rocket was launched into a breakup aurora at magnetic local midnight on 21 March 1968. The rocket was instrumented to measure electrons with an electrostatic analyzer electron spectrometer which made 29 measurements in the energy interval 0.5 KeV to 30 KeV. Complete energy spectra were obtained at a rate of 10/sec. Pitch angle information is presented via 3 computed average per rocket spin. The dumped electron average corresponds to averages over electrons moving nearly parallel to the B vector. The mirroring electron average corresponds to averages over electrons moving nearly perpendicular to the B vector. The average was also computed over the entire downward hemisphere (the precipitated electron average). The observations were obtained in an altitude range of 10 km at 230 km altitude.

  12. Ionospheric Electron Heating Associated With Pulsating Auroras: Joint Optical and PFISR Observations

    NASA Astrophysics Data System (ADS)

    Liang, Jun; Donovan, E.; Reimer, A.; Hampton, D.; Zou, S.; Varney, R.

    2018-05-01

    In a recent study, Liang et al. (2017, https://doi.org/10.1002/2017JA024127) repeatedly identified strong electron temperature (Te) enhancements when Swarm satellites traversed pulsating auroral patches. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the F region plasma signatures related to pulsating auroras. On 19 March 2015 night, which contained multiple intervals of pulsating auroral activities, we identify a statistical trend, albeit not a one-to-one correspondence, of strong Te enhancements ( 500-1000 K) in the upper F region ionosphere during the passages of pulsating auroras over PFISR. On the other hand, there is no discernible and repeatable density enhancement in the upper F region during pulsating auroral intervals. Collocated optical and NOAA satellite observations suggest that the pulsating auroras are composed of energetic electron precipitation with characteristic energy >10 keV, which is inefficient in electron heating in the upper F region. Based upon PFISR observations and simulations from Liang et al. (2017) model, we propose that thermal conduction from the topside ionosphere, which is heated by precipitating low-energy electrons, offers the most likely explanation for the observed electron heating in the upper F region associated with pulsating auroras. Such a heating mechanism is similar to that underlying the "stable auroral red arcs" in the subauroral ionosphere. Our proposal conforms to the notion on the coexistence of an enhanced cold plasma population and the energetic electron precipitation, in magnetospheric flux tubes threading the pulsating auroral patch. In addition, we find a trend of enhanced ion upflows during pulsating auroral intervals.

  13. Using field-particle correlations to study auroral electron acceleration in the LAPD

    NASA Astrophysics Data System (ADS)

    Schroeder, J. W. R.; Howes, G. G.; Skiff, F.; Kletzing, C. A.; Carter, T. A.; Vincena, S.; Dorfman, S.

    2017-10-01

    Resonant nonlinear Alfvén wave-particle interactions are believed to contribute to the acceleration of auroral electrons. Experiments in the Large Plasma Device (LAPD) at UCLA have been performed with the goal of providing the first direct measurement of this nonlinear process. Recent progress includes a measurement of linear fluctuations of the electron distribution function associated with the production of inertial Alfvén waves in the LAPD. These linear measurements have been analyzed using the field-particle correlation technique to study the nonlinear transfer of energy between the Alfvén wave electric fields and the electron distribution function. Results of this analysis indicate collisions alter the resonant signature of the field-particle correlation, and implications for resonant Alfvénic electron acceleration in the LAPD are considered. This work was supported by NSF, DOE, and NASA.

  14. Diverse Electron and Ion Acceleration Characteristics Observed Over Jupiter's Main Aurora

    NASA Astrophysics Data System (ADS)

    Mauk, B. H.; Haggerty, D. K.; Paranicas, C.; Clark, G.; Kollmann, P.; Rymer, A. M.; Peachey, J. M.; Bolton, S. J.; Levin, S. M.; Adriani, A.; Allegrini, F.; Bagenal, F.; Bonfond, B.; Connerney, J. E. P.; Ebert, R. W.; Gladstone, G. R.; Kurth, W. S.; McComas, D. J.; Ranquist, D.; Valek, P.

    2018-02-01

    Two new Juno-observed particle features of Jupiter's main aurora demonstrate substantial diversity of processes generating Jupiter's mysterious auroral emissions. It was previously speculated that sometimes-observed potential-driven aurora (up to 400 kV) can turn into broadband stochastic acceleration (dominating at Jupiter) by means of instability. Here direct evidence for such a process is revealed with a "mono-energetic" electron inverted-V rising in energy to 200 keV, transforming into a region of broadband acceleration with downward energy fluxes tripling to 3,000 mW/m2, and then transforming back into a mono-energetic structure ramping down from 200 keV. But a second feature of interest observed nearby is unlikely to have operated in the same way. Here a downward accelerated proton inverted-V, with inferred potentials to 300-400 kV, occurred simultaneously with downward accelerated broadband electrons with downward energy fluxes as high as any observed ( 3,000 mW/m2). This latter feature has no known precedent with Earth auroral observations.

  15. Observations of ionospheric electron beams in the plasma sheet.

    PubMed

    Zheng, H; Fu, S Y; Zong, Q G; Pu, Z Y; Wang, Y F; Parks, G K

    2012-11-16

    Electrons streaming along the magnetic field direction are frequently observed in the plasma sheet of Earth's geomagnetic tail. The impact of these field-aligned electrons on the dynamics of the geomagnetic tail is however not well understood. Here we report the first detection of field-aligned electrons with fluxes increasing at ~1 keV forming a "cool" beam just prior to the dissipation of energy in the current sheet. These field-aligned beams at ~15 R(E) in the plasma sheet are nearly identical to those commonly observed at auroral altitudes, suggesting the beams are auroral electrons accelerated upward by electric fields parallel (E([parallel])) to the geomagnetic field. The density of the beams relative to the ambient electron density is δn(b)/n(e)~5-13% and the current carried by the beams is ~10(-8)-10(-7) A m(-2). These beams in high β plasmas with large density and temperature gradients appear to satisfy the Bohm criteria to initiate current driven instabilities.

  16. Acceleration and Precipitation of Electrons during Substorm Dipolarization Events

    NASA Astrophysics Data System (ADS)

    Ashour-Abdalla, Maha; Richard, Robert; Donovan, Eric; Zhou, Meng; Goldstein, Mevlyn; El-Alaoui, Mostafa; Schriver, David; Walker, Raymond

    Observations and modeling have established that during geomagnetically disturbed times the Earth’s magnetotail goes through large scale changes that result in enhanced electron precipitation into the ionosphere and earthward propagating dipolarization fronts that contain highly energized plasma. Such events originate near reconnection regions in the magnetotail at about 20-30 R_E down tail. As the dipolarization fronts propagate earthward, strong acceleration of both ions and electrons occurs due to a combination of non-adiabatic and adiabatic (betatron and Fermi) acceleration, with particle energies reaching up to 100 keV within the dipolarization front. One consequence of the plasma transport that occurs during these events is direct electron precipitation into the ionosphere, which form auroral precipitation. Using global kinetic simulations along with spacecraft and ground-based data, causes of electron precipitation are determined during well-documented, disturbed events. It is found that precipitation of keV electrons in the pre-midnight sector at latitudes around 70(°) occur due to two distinct physical processes: (1) higher latitude (≥72(°) ) precipitation due to electrons that undergo relatively rapid non-adiabatic pitch angle scattering into the loss cone just earthward of the reconnection region at around 20 R_E downtail, and (2) lower latitude (≤72(°) ) precipitation due to electrons that are more gradually accelerated primarily parallel to the geomagnetic field during its bounce motion by Fermi acceleration and enter the loss cone much closer to the Earth at 10-15 R_E, somewhat tailward of the dipolarization front. As the dipolarization fronts propagate earthward, the electron precipitation shifts to lower latitudes and occurs over a wider region in the auroral ionosphere. Our results show a direct connection between electron acceleration in the magnetotail and electron precipitation in the ionosphere during disturbed times. The electron

  17. 1978 Diffuse Auroral Boundaries and a Derived Auroral Boundary Index

    DTIC Science & Technology

    1982-12-28

    they have nothing to do with the auroral precipitation, they must be differentiated from the auroral electrons when determining boundaries. Due to the...47.8 -54.6 -61.4 -68.0 -74.2 -79.4 -81.7 -78.9 -73.5 - 7.2 -60.6 GLON 121.0 118.5 115 S 1114 105.3 95.0 74.69 37.7 352.2 332.? 323:.1 317:3 M1LAY -56.2...1IN NN 1 1 NI M- I II- IN - N1 C , S~li-o N nol- O) N.010 DTN440 W00CO0 10011aN IIU0 )0 r,0 0 N0 t N1e . 0 MC0t)O0 r- ,J o 110 00 toC 0 0010 01 0t n 1

  18. Spatial relationship of field-aligned currents, electron precipitation, and plasma convection in the auroral oval

    NASA Technical Reports Server (NTRS)

    Coley, W. R.

    1983-01-01

    Observations reported by Winningham et al. (1975) have established that the auroral oval mapped to the magnetosphere along closed field lines divided the oval into two distinct regions of particle precipitation. In order to determine relationships between field-aligned current, convection, and particle precipitation, simultaneous measurements of all quantities are needed. The studies of Bythrow et al. (1980, 1981) have utilized Atmosphere Explorer C data for sunlit passes of the high-latitude ionosphere. The addition of magnetometer information for the eclipsed high-latitude passes of the Atmospheric Explorer C spacecraft makes it possible to make simultaneous measurements of Birkeland currents, plasma convection, and electron precipitation in the nightside auroral oval and polar cap. The present investigation provides the results of such observations, discusses the observed relationships, and attempts to correlate boundaries.

  19. Solar wind ∼0.1-1.5 keV electrons at quiet times

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tao, Jiawei; Wang, Linghua, E-mail: wanglhwang@gmail.com; Zong, Qiugang

    2016-03-25

    We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1-1.5 keV) electrons measured by the WIND 3-D Plasma & Energetic Particle (3DP) instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. Firstly, we separate strahl (beaming) electrons and halo (isotropic) electrons based on their features in pitch angle distributions. Secondly, we fit the observed energy spectrum of both the strahl and halo electrons at ∼0.1-1.5 keV to a Kappa distribution function with an index κ, effective temperature T{sub eff} and density n{sub 0}. We also integrate themore » the measurements over ∼0.1-1.5 keV to obtain the average electron energy E{sub avg} of the strahl and halo. We find a strong positive correlation between κ and T{sub eff} for both the strahl and halo, possibly reflecting the nature of the generation of these suprathermal electrons. Among the 245 selected samples, ∼68% have the halo κ smaller than the strahl κ, while ∼50% have the halo E{sub h} larger than the strahl E{sub s}.« less

  20. Auroral Data Analysis.

    DTIC Science & Technology

    1978-01-04

    evaluating Opal, C. B ., W. K . Peterson , and E. C. Beatty, thia paper, Measurement of secondary electron spectra Ref erences produced by electron...Polar Torbet , R. B ., K . A. Anderson, and C. W. cap auroral electron flu xes observed with Carlson, Observations of low and medium Isis 1, 3. Geophys. Res...STATES AIR FORCE HANSCOM AYE , MASSACHUS~~ 2S 01731 B . ~~~~~~~~~~~~~~~~~~~ ~~ — ~ —.-- a Qual ified requestora may obtain additional copies from the

  1. Effects of turbulence on a kinetic auroral arc model

    NASA Technical Reports Server (NTRS)

    Cornwall, J. M.; Chiu, Y. T.

    1981-01-01

    A plasma kinetic model of an inverted-V auroral arc structure which includes the effects of electrostatic turbulence is proposed. In the absence of turbulence, a parallel potential drop is supported by magnetic mirror forces and charge quasi neutrality, with energetic auroral ions penetrating to low altitudes; relative to the electrons, the ions' pitch angle distribution is skewed toward smaller pitch angles. The electrons energized by the potential drop form a current which excites electrostatic turbulence. In equilibrium the plasma is marginally stable. The conventional anomalous resistivity contribution to the potential drop is very small. Anomalous resistivity processes are far too dissipative to be powered by auroral particles. It is concluded that under certain circumstances equilibrium may be impossible and relaxation oscillations set in.

  2. FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

    2003-01-01

    The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identi@ the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral Snapshot (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data were used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and/or a long-system particle in cell simulation to model the magnetically connected region between the two satellites. Results from the study indicate that there are three main drivers of auroral acceleration: (1) field-aligned currents that lead to quasistatic parallel potential drops (parallel electric fields), (2) earthward flow of high-energy plasma beams from the magnetotail into the auroral zone that lead to quasistatic parallel potential drops, and (3) large-amplitude Alfven waves that propagate into the auroral region from the magnetotail. The events examined thus far confm the previously established invariant latitudinal dependence of the drivers and show a strong dependence on magnetic activity. Alfven waves tend to occur primarily at the poleward edge of the auroral region during more magnetically active times and are correlated with intense electron precipitation. At lower latitudes away

  3. VLF-HISS from electrons in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Maeda, K.

    1973-01-01

    Intensities of auroral and magnetospheric hiss generated by the Cherenkov radiation process of electrons in the lower magnetosphere were calculated with respect to a realistic model of the earth's magnetosphere. In this calculation, the magnetic field was expressed by the Mead-Fairfield Model, and a static model of the iono-magnetospheric plasma distribution was constructed by accumulated data obtained by recent satellite observations. The energy range of hiss producing electrons and the frequency range of produced VLF in the computation are 100 eV to 200 keV, and 2 to 200 kHz, respectively. The maximum hiss intensity produced by soft electrons is more than one order higher than that of hard electron produced hiss. Higher rate of hiss occurrence in the daytime side, particularly in the soft electron precipitation zone in the morning sector, and less association of auroral hiss in nighttime sectors must be, therefore, due to the local time dependence of the energy spectra of precipitating electrons rather than the difference in the geomagnetic field and in the geoplasma distributions.

  4. ELF wave production by an electron beam emitting rocket system and its suppression on auroral field lines - Evidence for Alfven and drift waves

    NASA Astrophysics Data System (ADS)

    Winckler, J. R.; Erickson, K. N.; Abe, Y.; Steffen, J. E.; Malcolm, P. R.

    1985-07-01

    Orthogonal probes on a free-flying plasma diagnostics payload are used to study ELF electric disturbances in the auroral ionosphere that are due to the injection of powerful electron beams. Frequency spectrograms are presented for various pitch angles, pulsing characteristics, and other properties of the injected beams; the large scale DC ionospheric convection electric field is measured, together with auroral particle precipitation, visual auroral forms, and ionospheric parameters. In view of the experimental results obtained, it is postulated that the observed ELF waves are in the Alfven and drift modes, and are generated by the positive vehicle potential during beam injection.

  5. Auroral-particle precipitation and trapping caused by electrostatic double layers in the ionosphere.

    PubMed

    Albert, R D; Lindstrom, P J

    1970-12-25

    Interpretation of high-resolution angular distribution measurements of the primary auroral electron flux detected by a rocket probe launched into a visible aurora from Fort Churchill in the fall of 1966 leads to the following conclusions. The auroral electron flux is nearly monoenergetic and has a quasi-trapped as well as a precipitating component. The quasi-trapped flux appears to be limited to a region defined by magnetic-mirror points and multiple electrostatic double layers in the ionosphere. The electrostatic field of the double-layer distribution enhances the aurora by lowering the magnetic-mirror points and supplying energy to the primary auroral electrons.

  6. First light from a kilometer-baseline Scintillation Auroral GPS Array.

    PubMed

    Datta-Barua, S; Su, Y; Deshpande, K; Miladinovich, D; Bust, G S; Hampton, D; Crowley, G

    2015-05-28

    We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100-1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed.

  7. Extremely Nonthermal Monoenergetic Precipitation in the Auroral Acceleration Region: In Situ Observations

    NASA Astrophysics Data System (ADS)

    Hatch, S.; Chaston, C. C.; Labelle, J. W.

    2017-12-01

    We report in situ measurements through the auroral acceleration region that reveal extremely nonthermal monoenergetic electron distributions. These auroral primaries are indicative of source populations in the plasma sheet well described as kappa distributions with κ ≲ 2. We show from observations and modeling how this large deviation from Maxwellian form may modify the acceleration potential required to drive current closure through the auroral ionosphere.

  8. The Auroral Field-aligned Acceleration - Cluster Results

    NASA Astrophysics Data System (ADS)

    Vaivads, A.; Cluster Auroral Team

    The four Cluster satellites cross the auroral field lines at altitudes well above most of acceleration region. Thus, the orbit is appropriate for studies of the generator side of this region. We consider the energy transport towards the acceleration region and different mechanisms for generating the potential drop. Using data from Cluster we can also for the first time study the dynamics of the generator on a minute scale. We present data from a few auroral field crossings where Cluster are in conjunction with DMSP satellites. We use electric and magnetic field data to estimate electrostatic po- tential along the satellite orbit, Poynting flux as well as the presence of plasma waves. These we can compare with data from particle and wave instruments on Cluster and on low latitude satellites to try to make a consistent picture of the acceleration region formation in these cases. Preliminary results show close agreement both between in- tegrated potential values at Cluster and electron peak energies at DMSP as well as close agreement between the integrated Poynting flux values at Cluster and the elec- tron energy flux at DMSP. At the end we draw a parallels between auroral electron acceleration and electron acceleration at the magnetopause.

  9. Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

    NASA Technical Reports Server (NTRS)

    Kaeppler, S. R.; Kletzing, C. A.; Bounds, S. R.; Gjerloev, J. W.; Anderson, B. J.; Korth, H.; LaBelle, J. W.; Dombrowski, M. P.; Lessard, M.; Pfaff, R. F.; hide

    2012-01-01

    The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission was designed to observe electrodynamic and plasma parameters above and within the current closure region of the auroral ionosphere. Two well instrumented payloads were flown along very similar magnetic field footprints, at different altitudes, with small temporal separation between both payloads. The higher altitude payload (apogee 360 km), obtained in-situ measurements of electrodynamic and plasma parameters above the current closure region to determine the input signature. The low altitude payload (apogee 130 km), made similar observations within the current closure region. Results are presented comparing observations of the electric fields, magnetic components, and the differential electron energy flux at magnetic footpoints common to both payloads. In situ data is compared to the ground based all-sky imager data, which presents the evolution of the auroral event as the payloads traversed through magnetically similar regions. Current measurements derived from the magnetometers on the high altitude payload observed upward and downward field-aligned currents. The effect of collisions with the neutral atmosphere is investigated to determine if it is a significant mechanism to explain discrepancies in the low energy electron flux. The high altitude payload also observed time-dispersed arrivals in the electron flux and perturbations in the electric and magnetic field components, which are indicative of Alfven waves.

  10. Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

    NASA Technical Reports Server (NTRS)

    Kaeppler, S. R.; Kletzing, C. A.; Bounds, S. R.; Gjerloev, J. W.; Anderson, B. J.; Korth, H.; LaBelle, J. W.; Dombrowski, M. P.; Lessard, M.; Pfaff, R. F.; hide

    2011-01-01

    The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission was designed to observe electrodynamic and plasma parameters above and within the current closure region of the auroral ionosphere. Two well instrumented payloads were flown along very similar magnetic field footprints, at different altitudes, with small temporal separation between both payloads. The higher altitude payload (apogee 360 km), obtained in-situ measurements of electrodynamic and plasma parameters above the current closure region to determine the input signature. The low altitude payload (apogee 130 km), made similar observations within the current closure region. Results are presented comparing observations of the electric fields, magnetic components, and the differential electron energy flux at magnetic footpoints common to both payloads. In situ data is compared to the ground based all-sky imager data, which presents the evolution of the auroral event as the payloads traversed through magnetically similar regions. Current measurements derived from the magnetometers on the high altitude payload observed upward and downward field-aligned currents. The effect of collisions with the neutral atmosphere is investigated to determine it is a significant mechanism to explain discrepancies in the low energy electron flux. The high altitude payload also observed time-dispersed arrivals in the electron flux and perturbations in the electric and magnetic field components, which are indicative of Alfven waves.

  11. Magnetospheric and auroral plasmas - A short survey of progress

    NASA Technical Reports Server (NTRS)

    Frank, L. A.

    1975-01-01

    Important milestones in our researches of auroral and magnetospheric plasmas for the past quadrennium 1971-1975 are reviewed. Many exciting findings, including those of the polar cusp, the polar wind, the explosive disruptions of the magnetotail, the interactions of hot plasmas with the plasmapause, the auroral field-aligned currents, and the striking inverted V electron precipitation events, were reported during this period. Solutions to major questions concerning the origins and acceleration of these plasmas appear possible in the near future. A comprehensive bibliography of current research is appended to this brief survey of auroral and magnetospheric plasmas.

  12. First light from a kilometer-baseline Scintillation Auroral GPS Array

    PubMed Central

    Datta-Barua, S; Su, Y; Deshpande, K; Miladinovich, D; Bust, G S; Hampton, D; Crowley, G

    2015-01-01

    We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100–1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. Key Points A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed PMID:26709318

  13. Numerically simulated two-dimensional auroral double layers

    NASA Technical Reports Server (NTRS)

    Borovsky, J. E.; Joyce, G.

    1983-01-01

    A magnetized 2 1/2-dimensional particle-in-cell system which is periodic in one direction and bounded by reservoirs of Maxwellian plasma in the other is used to numerically simulate electrostatic plasma double layers. For the cases of both oblique and two-dimensional double layers, the present results indicate periodic instability, Debye length rather than gyroradii scaling, and low frequency electrostatic turbulence together with electron beam-excited electrostatatic electron-cyclotron waves. Estimates are given for the thickness of auroral doule layers, as well as the separations within multiple auroral arcs. Attention is given to the temporal modulation of accelerated beams, and the possibilities for ion precipitation and ion conic production by the double layer are hypothesized. Simulations which include the atmospheric backscattering of electrons imply the action of an ionospheric sheath which accelerates ionospheric ions upward.

  14. Quiet-Time Suprathermal ( 0.1-1.5 keV) Electrons in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Wang, L.; Tao, J.; Zong, Q.; Li, G.; Salem, C. S.; Wimmer-Schweingruber, R. F.; He, J.; Tu, C.; Bale, S. D.

    2016-12-01

    We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-1.5 keV) electrons measured by the WIND/3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ˜0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature Teff. We also calculate the number density n and average energy Eavg of strahl and halo electrons by integrating the electron measurements between ˜0.1 and 1.5 keV. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

  15. Quiet-time Suprathermal (~0.1-1.5 keV) Electrons in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Tao, Jiawei; Wang, Linghua; Zong, Qiugang; Li, Gang; Salem, Chadi S.; Wimmer-Schweingruber, Robert F.; He, Jiansen; Tu, Chuanyi; Bale, Stuart D.

    2016-03-01

    We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ˜0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature Teff. We also calculate the number density n and average energy Eavg of strahl and halo electrons by integrating the electron measurements between ˜0.1 and 1.5 keV. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

  16. Proximity functions for electrons up to 10 keV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chmelevsky, D.; Kellerer, A.M.; Terrissol, M.

    1980-11-01

    Proximity functions for electrons up to 10 keV in water are computed from simulated particle tracks. Numerical results are given for the differential functions t(x) and the integral functions T(x). Basic characteristics of these functions and their connections to other microdosimetric quantities are considered. As an example of the applicability of the proximity functions, the quantity y/sub D/ for spheres is derived from t(x).

  17. Rocket experiments for spectral estimation of electron density fine structure in the auroral and equatorial ionosphere and preliminary results

    NASA Technical Reports Server (NTRS)

    Tomei, B. A.; Smith, L. G.

    1986-01-01

    Sounding rockets equipped to monitor electron density and its fine structure were launched into the auroral and equatorial ionosphere in 1980 and 1983, respectively. The measurement electronics are based on the Langmuir probe and are described in detail. An approach to the spectral analysis of the density irregularities is addressed and a software algorithm implementing the approach is given. Preliminary results of the analysis are presented.

  18. Relativistic Electron Precipitation in the Auroral Zone. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Simons, D. J.

    1975-01-01

    The energy spectra and pitch angle distributions of electrons in the energy range from 50 keV to 2 MeV were determined by a solid state electron energy spectrometer during the Relativistic Electron Precipitation (REP) event of 31 May 1972. The pitch angle distributions were determined from a knowledge of the rocket aspect and the direction in space of the earth's magnetic field. The rocket aspect determination was therefore treated in depth and a method was developed to compensate for the malfunctioning of the aspect magnetometer. The electron fluxes during the REP event were highly variable demonstrating correlated energy, flux, and pitch angle pulsations with time periods of less than one second. A theoretical model for the production of relativistic electrons was proposed. It follows from this model that, at comparatively low background electron densities, the anomalous Doppler resonance leads to the acceleration of near relativistic particles.

  19. Flux Enhancements of > 30 keV Electrons at Low Drift Shells L < 1.2 During Last Solar Cycles

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.

    2017-12-01

    We present results of statistical analysis of enhancements of >30 keV electrons observed by the NOAA/POES satellites during solar cycles 23 and 24 (1998-2016) at low drift shells L < 1.2, so-called forbidden zone. We collected 1,750 days ( 25% of the total time) when fluxes of the forbidden energetic electrons (FEE) exceeded 103 (cm2 s sr)-1. We found 530 days, when FEE fluxes reached high intensity from 104 up to 107 (cm2 s sr)-1. It was found that the FEE enhancements were observed mostly often at the declining phases and solar minimum. More than 85% of the events occurred under fast solar wind (V > 450 km/s), high substorm activity (AL >150 nT), and enhanced interplanetary electric field perturbations (VδB > 1.5 mV/m). The FEE occurrence rate peaks around the local midnight. We have also found a quite unexpected annual variation of the FEE occurrence rate with a pronounced maximum from May to September, a minor peak in December-January, and minima at the equinoxes. The May-September peak, persisting at different solar cycle phases, was assumed to originate from high conductivity in the auroral ionosphere, which is controlled by the dipole tilt angle and provides better conditions for penetration of electric field perturbations into the inner magnetosphere. This allows explanation of the shape and amplitude of annual variation in the FEE occurrence rate from the convolution of the solar wind driver with the penetration conditions.

  20. Electron-driven excitation of O 2 under night-time auroral conditions: Excited state densities and band emissions

    NASA Astrophysics Data System (ADS)

    Jones, D. B.; Campbell, L.; Bottema, M. J.; Teubner, P. J. O.; Cartwright, D. C.; Newell, W. R.; Brunger, M. J.

    2006-01-01

    Electron impact excitation of vibrational levels in the ground electronic state and seven excited electronic states in O 2 have been simulated for an International Brightness Coefficient-Category 2+ (IBC II+) night-time aurora, in order to predict O 2 excited state number densities and volume emission rates (VERs). These number densities and VERs are determined as a function of altitude (in the range 80-350 km) in the present study. Recent electron impact excitation cross-sections for O 2 were combined with appropriate altitude dependent IBC II+ auroral secondary electron distributions and the vibrational populations of the eight O 2 electronic states were determined under conditions of statistical equilibrium. Pre-dissociation, atmospheric chemistry involving atomic and molecular oxygen, radiative decay and quenching of excited states were included in this study. This model predicts relatively high number densities for the X3Σg-(v'⩽4),a1Δandb1Σg+ metastable electronic states and could represent a significant source of stored energy in O 2* for subsequent thermospheric chemical reactions. Particular attention is directed towards the emission intensities of the infrared (IR) atmospheric (1.27 μm), Atmospheric (0.76 μm) and the atomic oxygen 1S→ 1D transition (5577 Å) lines and the role of electron-driven processes in their origin. Aircraft, rocket and satellite observations have shown both the IR atmospheric and Atmospheric lines are dramatically enhanced under auroral conditions and, where possible, we compare our results to these measurements. Our calculated 5577 Å intensity is found to be in good agreement with values independently measured for a medium strength IBC II+ aurora.

  1. Modeling of Jovian Auroral Polar Ion and Proton Precipitation

    NASA Astrophysics Data System (ADS)

    Houston, S. J.; Ozak, N. O.; Cravens, T.; Schultz, D. R.; Mauk, B.; Haggerty, D. K.; Young, J. T.

    2017-12-01

    Auroral particle precipitation dominates the chemical and physical environment of the upper atmospheres and ionospheres of the outer planets. Precipitation of energetic electrons from the middle magnetosphere is responsible for the main auroral oval at Jupiter, but energetic electron, proton, and ion precipitation take place in the polar caps. At least some of the ion precipitation is associated with soft X-ray emission with about 1 GW of power. Theoretical modeling has demonstrated that the incident sulfur and oxygen ion energies must exceed about 0.5 MeV/nucleon (u) in order to produce the measured X-ray emission. In this work we present a model of the transport of magnetospheric oxygen ions as they precipitate into Jupiter's polar atmosphere. We have revised and updated the hybrid Monte Carlo model originally developed by Ozak et al., 2010 to model the Jovian X-ray aurora. We now simulate a wider range of incident oxygen ion energies (10 keV/u - 5 MeV/u) and update the collision cross-sections to model the ionization of the atmospheric neutrals. The polar cap location of the emission and magnetosphere-ionosphere coupling both indicate the associated field-aligned currents must originate near the magnetopause or perhaps the distant tail. Secondary electrons produced in the upper atmosphere by ion precipitation could be accelerated upward to relativistic energies due to the same field-aligned potentials responsible for the downward ion acceleration. To further explore this, we simulate the effect of the secondary electrons generated from the heavy ion precipitation. We use a two-stream transport model that computes the secondary electron fluxes, their escape from the atmosphere, and characterization of the H2 Lyman-Werner band emission, including a predicted observable spectrum with the associated color ratio. Our model predicts that escaping electrons have an energy range from 1 eV to 6 keV, H2 band emission rates produced are on the order of 75 kR for an input

  2. An explanation of auroral intensification during the substorm expansion phase

    NASA Astrophysics Data System (ADS)

    Yao, Zhonghua; Rae, I. J.; Lui, A. T. Y.; Murphy, K. R.; Owen, C. J.; Pu, Z. Y.; Forsyth, C.; Grodent, D.; Zong, Q.-G.; Du, A. M.; Kalmoni, N. M. E.

    2017-08-01

    A multiple auroral onset substorm on 28 March 2010 provides an opportunity to understand the physical mechanism in generating auroral intensifications during a substorm expansion phase. Conjugate observations of magnetic fields and plasma from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, of field-aligned currents (FACs) from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellites, and from ground-based magnetometers and aurora are all available. The comprehensive measurements allow us to further our understanding of the complicated causalities among dipolarization, FAC generation, particle acceleration, and auroral intensification. During the substorm expansion phase, the plasma sheet expanded and was perturbed leading to the generation of a slow mode wave, which modulated electron flux in the outer plasma sheet. During this current sheet expansion, field-aligned currents formed, and geomagnetic perturbations were simultaneously detected by ground-based instruments. However, a magnetic dipolarization did not occur until about 3 min later in the outer plasma sheet observed by THEMIS-A spacecraft (THA). We believe that this dipolarization led to an efficient Fermi acceleration to electrons and consequently the cause of a significant auroral intensification during the expansion phase as observed by the All-Sky Imagers (ASIs). This Fermi acceleration mechanism operating efficiently in the outer plasma sheet during the expansion phase could be a common explanation of the poleward auroral development after substorm onset. These results also show a good agreement between the upward FAC derived from AMPERE measurements and the auroral brightening observed by the ASIs.

  3. Observation of atomic oxygen O(1S) green-line emission in the summer polar upper mesosphere associated with high-energy (≥30 keV) electron precipitation during high-speed solar wind streams

    NASA Astrophysics Data System (ADS)

    Lee, Young-Sook; Kwak, Young-Sil; Kim, Kyung-Chan; Solheim, Brian; Lee, Regina; Lee, Jaejin

    2017-01-01

    The auroral green-line emission at 557.7 nm wavelength as arising from the atomic oxygen O(1S → 1D) transition typically peaks at an altitude of 100 km specifically in the nightside oval, induced by auroral electrons within an energy range of 100 eV-30 keV. Intense aurora is known as being suppressed by sunlight in summer daytime but usually occurs in low electrical background conductivity. However, in the present study in summer (July) sunlit condition, enhancements of O(1S) emission rates observed by using the Wind Imaging Interferometer/UARS were frequently observed at low altitudes below 90 km, where ice particles are created initially as subvisible and detected as polar mesosphere summer echoes, emerging to be an optical phenomenon of polar mesospheric clouds. The intense O(1S) emission occurring in summer exceeds those occurring in the daytime in other seasons both in occurrence and in intensity, frequently accompanied by occurrences of supersonic neutral velocity (300-1500 m s-1). In the mesosphere, ion motion is controlled by electric field and the momentum is transferred to neutrals. The intense O(1S) emission is well associated with high-energy electron precipitation as observed during an event of high-speed solar wind streams. Meanwhile, since the minimum occurrences of O(1S) emission and supersonic velocity are maintained even in the low precipitation flux, the mechanism responsible is not only related to high-energy electron precipitation but also presumably to the local conditions, including the composition of meteoric-charged ice particles and charge separation expected in extremely low temperatures (<150 K).

  4. Sub-Auroral Polarization Stream (SAPS) Events Under Non-storm Conditions

    NASA Astrophysics Data System (ADS)

    Sazykin, S. Y.; Coster, A. J.; Huba, J.; Spiro, R. W.; Baker, J. B.; Kunduri, B.; Ruohoniemi, J. M.; Erickson, P. J.; Wolf, R.

    2017-12-01

    The occurrence of Sub-Auroral Polarization Stream, or SAPS, structures, defined here as latitudinally narrow channels of enhanced westward plasma convection in the evening ionosphere equatorward of the auroral electron precipitation boundary, is most dramatic during geomagnetic storms. However, SAPS-like structures known as Polarization Jets or SAIDs (Sub-Auroral Ion Drift events) are also frequently observed during non-storm conditions, typically during periods of isolated substorm activity or during bursts of enhanced convection associated with southward IMF Bz component. This paper presents results from data analysis and numerical simulations of several SAPS/SAID events observed during non-storm conditions. We use convection velocity measurements from the mid-latitude chain of SuperDARN radars and cross-track drift meter data from DMSP spacecraft to identify SAPS/SAID and to characterize their structure and temporal evolution. DMSP topside ion density data and high-resolution ground-based GPS total electron content (TEC) maps are used to determine the ionospheric and plasmaspheric morphology of SAPS regions. DMSP electron precipitation data are used to determine auroral boundaries. We also present simulation results of the chosen event intervals obtained with the SAMI3-RCM ionosphere-magnetosphere coupled model. Observational results are analyzed to identify systematic differences between non-storm SAPS/SAID and the picture that has emerged based on previous storm time studies. Simulation results are used to provide physical interpretation of these differences.

  5. On the Monte Carlo simulation of electron transport in the sub-1 keV energy range.

    PubMed

    Thomson, Rowan M; Kawrakow, Iwan

    2011-08-01

    The validity of "classic" Monte Carlo (MC) simulations of electron and positron transport at sub-1 keV energies is investigated in the context of quantum theory. Quantum theory dictates that uncertainties on the position and energy-momentum four-vectors of radiation quanta obey Heisenberg's uncertainty relation; however, these uncertainties are neglected in "classical" MC simulations of radiation transport in which position and momentum are known precisely. Using the quantum uncertainty relation and electron mean free path, the magnitudes of uncertainties on electron position and momentum are calculated for different kinetic energies; a validity bound on the classical simulation of electron transport is derived. In order to satisfy the Heisenberg uncertainty principle, uncertainties of 5% must be assigned to position and momentum for 1 keV electrons in water; at 100 eV, these uncertainties are 17 to 20% and are even larger at lower energies. In gaseous media such as air, these uncertainties are much smaller (less than 1% for electrons with energy 20 eV or greater). The classical Monte Carlo transport treatment is questionable for sub-1 keV electrons in condensed water as uncertainties on position and momentum must be large (relative to electron momentum and mean free path) to satisfy the quantum uncertainty principle. Simulations which do not account for these uncertainties are not faithful representations of the physical processes, calling into question the results of MC track structure codes simulating sub-1 keV electron transport. Further, the large difference in the scale at which quantum effects are important in gaseous and condensed media suggests that track structure measurements in gases are not necessarily representative of track structure in condensed materials on a micrometer or a nanometer scale.

  6. Application of X-ray imaging techniques to auroral monitoring

    NASA Technical Reports Server (NTRS)

    Rust, D. M.; Burstein, P.

    1981-01-01

    The precipitation of energetic particles into the ionosphere produces bremsstrahlung X-rays and K-alpha line emission from excited oxygen and nitrogen. If viewed from a spacecraft in a highly elliptical polar orbit, this soft (0.3 - 3.0 keV) X-radiation will provide an almost uninterrupted record of dayside and nightside auroras. A grazing incidence X-ray telescope especially designed for such auroral monitoring is described. High photon collection efficiency will permit exposure times of approximately 100 seconds during substorms. Spectrophotometry will allow users to derive the energy spectrum of the precipitating particles. If placed in a 15 earth-radius orbit, the telescope can produce auroral X-ray images with 30 km resolution. Absolute position of X-ray auroras can be established with a small optical telescope co-aligned with the X-ray telescope. Comparison of X-ray and optical images will establish the height and global distribution of X-ray aurorae, relative to well-known optical auroras, thus melding the new X-ray results with knowledge of optical auroras.

  7. Auroral Infrasound Observed at I53US at Fairbanks, Alaska

    NASA Astrophysics Data System (ADS)

    Wilson, C. R.; Olson, J. V.

    2003-12-01

    In this presentation we will describe two different types of auroral infrasound recently observed at Fairbanks, Alaska in the pass band from 0.015 to 0.10 Hz. Infrasound signals associated with auroral activity (AIW) have been observed in Fairbanks over the past 30 years with infrasonic microphone arrays. The installation of the new CTBT/IMS infrasonic array, I53US, at Fairbanks has resulted in a greatly increased quality of the infrasonic data with which to study natural sources of infrasound. In the historical data at Fairbanks all the auroral infrasonic waves (AIW) detected were found to be the result of bow waves that are generated by supersonic motion of auroral arcs that contain strong electrojet currents. This infrasound is highly anisotropic, moving in the same direction as that of the auroral arc. AIW bow waves observed in 2003 at I53US will be described. Recently at I53US we have observed many events of very high trace velocity that are comprised of continuous, highly coherent wave trains. These waves occur in the morning hours at times of strong auroral activity. This new type of very high trace velocity AIW appears to be associated with pulsating auroral displays. Pulsating auroras occur predominantly after magnetic midnight (10:00 UT at Fairbanks). They are a usual part of the recovery phase of auroral substorms and are produced by energetic electrons precipitating into the atmosphere. Given proper dark, cloudless sky conditions during the AIW events, bright pulsating auroral forms were sometimes visible overhead.

  8. DISCOVERY OF A DARK AURORAL OVAL ON SATURN

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The ultraviolet image was obtained by the NASA/ESA Hubble Space Telescope with the European Faint Object Camera (FOC) on June 1992. It represents the sunlight reflected by the planet in the near UV (220 nm). * The image reveals a dark oval encircling the north magnetic pole of Saturn. This auroral oval is the first ever observed for Saturn, and its darkness is unique in the solar system (L. Ben-Jaffel, V. Leers, B. Sandel, Science, Vol. 269, p. 951, August 18, 1995). The structure represents an excess of absorption of the sunlight at 220 nm by atmospheric particles that are the product of the auroral activity itself. The large tilt of the northern pole of Saturn at the time of observation, and the almost perfect symmetry of the planet's magnetic field, made this observation unique as even the far side of the dark oval across the pole is visible! * Auroral activity is usually characterized by light emitted around the poles. The dark oval observed for Saturn is a STUNNING VISUAL PROOF that transport of energy and charged particles from the magnetosphere to the atmosphere of the planet at high latitudes induces an auroral activity that not only produces auroral LIGHT but also UV-DARK material near the poles: auroral electrons are probably initiating hydrocarbon polymer formation in these regions. Credits: L. Ben Jaffel, Institut d'Astrophysique de Paris-CNRS, France, B. Sandel (Univ. of Arizona), NASA/ESA, and Science (magazine).

  9. Using the Medipix3 detector for direct electron imaging in the range 60 keV to 200 keV in electron microscopy

    NASA Astrophysics Data System (ADS)

    Mir, J. A.; Plackett, R.; Shipsey, I.; dos Santos, J. M. F.

    2017-11-01

    Hybrid pixel sensor technology such as the Medipix3 represents a unique tool for electron imaging. We have investigated its performance as a direct imaging detector using a Transmission Electron Microscope (TEM) which incorporated a Medipix3 detector with a 300 μm thick silicon layer compromising of 256×256 pixels at 55 μm pixel pitch. We present results taken with the Medipix3 in Single Pixel Mode (SPM) with electron beam energies in the range, 60-200 keV . Measurements of the Modulation Transfer Function (MTF) and the Detective Quantum Efficiency (DQE) were investigated. At a given beam energy, the MTF data was acquired by deploying the established knife edge technique. Similarly, the experimental data required to determine DQE was obtained by acquiring a stack of images of a focused beam and of free space (flatfield) to determine the Noise Power Spectrum (NPS).

  10. Quiet-Time Suprathermal (˜0.1 - 200 keV) Electrons in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Wang, Linghua; Yang, Liu; Tao, Jiawei; Zong, Qiugang; Li, Gang; Wimmer-Schweingruber, Robert; He, Jiansen; Tu, Chuanyi; Bale, Stuart

    2017-04-01

    We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-200 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. The observed energy spectrum of both (beaming) strahl and (isotropic) halo electrons at ˜0.1-1.5 keV generally fits to a Kappa distribution function with an index κ and effective temperature Teff, while the observed energy spectrum of nearly isotropic superhalo electrons at ˜20-200 keV generally fits to a power-law function, J ˜ E-β. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl density and halo density. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. For the superhalo population, the spectral index β ranges from ˜1.6 to ˜3.7 and the integrated density nsup ranges from 10-8 cm-3 to 10-5 cm-3, with no clear association with the sunspot number. In solar cycle 23 (24), the distribution of β has a broad maximum between 2.4 and 2.8 (2.0 and 2.4). All the strahl, halo and superhalo populations show no obvious correlation with the solar wind core population. These results reflect the nature of the generation of solar wind suprathermal electrons.

  11. Determination of auroral electrostatic potentials using high- and low-altitude particle distributions

    NASA Technical Reports Server (NTRS)

    Reiff, P. H.; Collin, H. L.; Craven, J. D.; Burch, J. L.; Winningham, J. D.

    1988-01-01

    The auroral electrostatic potential differences were determined from the particle distribution functions obtained nearly simultaneously above and below the auroral acceleration region by DE-1 at altitudes 9000-15,000 km and DE-2 at 400-800 km. Three independent techniques were used: (1) the peak energies of precipitating electrons observed by DE-2, (2) the widening of loss cones for upward traveling electrons observed by DE-1, and (3) the energies of upgoing ions observed by DE-1. The assumed parallel electrostatic potential difference calculated by the three methods was nearly the same. The results confirmed the hypothesis that parallel electrostatic fields of 1-10 kV potential drop at 1-2 earth radii altitude are an important source for auroral particle acceleration.

  12. Auroral particles

    NASA Technical Reports Server (NTRS)

    Evans, David S.

    1987-01-01

    The problems concerning the aurora posed prior to the war are now either solved in principle or were restated in a more fundamental form. The pre-war hypothesis concerning the nature of the auroral particles and their energies was fully confirmed, with the exception that helium and oxygen ions were identified as participating in the auroral particle precipitation in addition to the protons. The nature of the near-Earth energization processes affecting auroral particles was clarified. Charged particle trajectories in various electric field geometries were modeled. The physical problems have now moved from determining the nature and geometry of the electric fields, which accelerate charged particles near the Earth, to accounting for the existence of these electric fields as a natural consequence of the solar wind's interaction with Earth. Ultimately the reward in continuing the work in auroral and magnetospheric particle dynamics will be a deeper understanding of the subtleties of classical electricity and magnetism as applied to situations not blessed with well-defined and invariant geometries.

  13. Danish auroral science history

    NASA Astrophysics Data System (ADS)

    Stauning, P.

    2011-01-01

    Danish auroral science history begins with the early auroral observations made by the Danish astronomer Tycho Brahe during the years from 1582 to 1601 preceding the Maunder minimum in solar activity. Included are also the brilliant observations made by another astronomer, Ole Rømer, from Copenhagen in 1707, as well as the early auroral observations made from Greenland by missionaries during the 18th and 19th centuries. The relations between auroras and geomagnetic variations were analysed by H. C. Ørsted, who also played a vital role in the development of Danish meteorology that came to include comprehensive auroral observations from Denmark, Iceland and Greenland as well as auroral and geomagnetic research. The very important auroral investigations made by Sophus Tromholt are outlined. His analysis from 1880 of auroral observations from Greenland prepared for the significant contributions from the Danish Meteorological Institute, DMI, (founded in 1872) to the first International Polar Year 1882/83, where an expedition headed by Adam Paulsen was sent to Greenland to conduct auroral and geomagnetic observations. Paulsen's analyses of the collected data gave many important results but also raised many new questions that gave rise to auroral expeditions to Iceland in 1899 to 1900 and to Finland in 1900 to 1901. Among the results from these expeditions were 26 unique paintings of the auroras made by the artist painter, Harald Moltke. The expedition to Finland was headed by Dan la Cour, who later as director of the DMI came to be in charge of the comprehensive international geomagnetic and auroral observations made during the Second International Polar Year in 1932/33. Finally, the article describes the important investigations made by Knud Lassen during, among others, the International Geophysical Year 1957/58 and during the International Quiet Sun Year (IQSY) in 1964/65. With his leadership the auroral and geomagnetic research at DMI reached a high international

  14. Correlation between core ion energization, suprathermal electron bursts, and broadband ELF plasma waves

    NASA Astrophysics Data System (ADS)

    Knudsen, David J.; Clemmons, James H.; Wahlund, Jan-Erik

    1998-03-01

    Observations of the lowest energy or core ions provide a particularly sensitive measure of the early stages of auroral ion energization. Freja satellite observations of 0-20 eV core ions in the topside auroral ionosphere and cusp/cleft show signs of heating within both regions of VLF hiss and broadband ELF plasma waves. However, heating to several eV or more is associated predominantly with the ELF waves. A correlation analysis of wave and core ion data formed from orbital segments shows that, on average, correlations are highest for wave frequencies below several hundred Hz, and less at VLF hiss frequencies. A similar analysis shows a higher correlation between electron precipitation and ion heating for electron energies below several hundred eV (i.e., the energies associated with suprathermal electron bursts) and a lower correlation above the 1 keV energies associated with auroral inverted-V's. Signs of core ion heating begin to appear when wave power at the O+ gyrofrequency exceeds about 10-3(mVm-1)2/Hz, and when the integrated field-aligned electron flux exceeds a few times 107cm-2s-1sr-1. This electron energy flux threshold is at least an order of magnitude lower than previously inferred from earlier studies comparing suprathermal electron fluxes and energetic ions. Almost all observed heating events occur during enhanced or active geomagnetic conditions; i.e., Kp>=4. While the most intense core ion heating is correlated with broadband ELF waves, we also present one example of weak ion heating of a few eV in a region of VLF auroral hiss.

  15. Rocket measurement of auroral partial parallel distribution functions

    NASA Astrophysics Data System (ADS)

    Lin, C.-A.

    1980-01-01

    The auroral partial parallel distribution functions are obtained by using the observed energy spectra of electrons. The experiment package was launched by a Nike-Tomahawk rocket from Poker Flat, Alaska over a bright auroral band and covered an altitude range of up to 180 km. Calculated partial distribution functions are presented with emphasis on their slopes. The implications of the slopes are discussed. It should be pointed out that the slope of the partial parallel distribution function obtained from one energy spectra will be changed by superposing another energy spectra on it.

  16. Auroral oval kinematics program

    NASA Technical Reports Server (NTRS)

    Comfort, R. H.

    1972-01-01

    A computer program which determines the geographic location of the auroral oval for given universal time and level of geomagnetic activity was developed for use on the IBM 7094 computer. The program provides both printed output of geographic coordinates of auroral oval boundaries and polar plots of the auroral oval. In addition, there is available a time-integration option which indicates how long a given location is under the auroral oval during a specified period. A description is given of the program and its use.

  17. Generation of poleward moving auroral forms (PMAFs) during periods of dayside auroral oval expansions/contractions and periods when the dayside auroral oval is expanded and stable

    NASA Astrophysics Data System (ADS)

    Fasel, G. J.; Flicker, J.; Sibeck, D. G.; Alyami, M.; Angelo, A.; Aylward, R. J.; Bender, S.; Christensen, M.; Kim, J.; Kristensen, H.; Orellana, Y.; Sahin, O.; Yoon, J.; Green, D.; Sigernes, F.; Lorentzen, D. A.

    2013-12-01

    The latitude of the equatorial edge of the dayside auroral oval has been shown to vary with the direction of the IMF Bz-component. The equatorward/poleward edge of the dayside auroral oval shifts equatorward/poleward when the IMF Bz-component is negative/positive [Burch, 1973; Akasofu, 1977; Horwitz and Akasofu, 1977; Sandholt et al., 1986, 1988]. Past studies have shown that poleward-moving auroral forms (PMAFs) are a common feature during equatorward expansions of the dayside auroral oval. Horwitz and Akasofu [1977] noted a one-to-one correspondence of luminous PMAFs associated with an equatorward expansion of the dayside auroral oval. During the southward turning of the IMF Bz-component the merging rate on the dayside increases [Newell and Meng, 1987] leading to the erosion of the dayside magnetopause. The field line merging process is thought to be most efficient when the interplanetary magnetic field (IMF) Bz-component turns southward. Both Vorobjev et al. [1975] and Horwitz and Akasofu [1977] attributed these PMAFs to magnetic flux being eroded away from the dayside magnetopause and transported antisunward. Dayside poleward-moving auroral forms are also observed during periods of an expanded and stable dayside auroral oval for both northern and southern hemisphere observations [Sandholt et al., 1986, 1989, 1990; Rairden and Mende, 1989; Mende et al., 1990]. Poleward-moving auroral forms have also been observed during some dayside oval contractions but have not been discussed much in the literature. This study examines the dayside auroral oval during periods of expansion, contraction, and during periods of an expanded and stable dayside auroral oval. This statistical study will provide the following results: number of poleward-moving auroral forms that are generated during dayside auroral oval expansions/contractions and during periods of a stable and expanded dayside auroral oval, the average initial and final elevation angle of the dayside auroral oval, time

  18. New DMSP database of precipitating auroral electrons and ions

    NASA Astrophysics Data System (ADS)

    Redmon, Robert J.; Denig, William F.; Kilcommons, Liam M.; Knipp, Delores J.

    2017-08-01

    Since the mid-1970s, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low Earth orbit. As the program evolved, so have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides. These are provided in a common and self-describing format that covers 30+ years of DMSP spacecraft from F06 (launched in 1982) to F18 (launched in 2009). This new database is accessible at the National Centers for Environmental Information and the Coordinated Data Analysis Web. We describe how the new database is being applied to high-latitude studies of the colocation of kinetic and electromagnetic energy inputs, ionospheric conductivity variability, field-aligned currents, and auroral boundary identification. We anticipate that this new database will support a broad range of space science endeavors from single observatory studies to coordinated system science investigations.

  19. New DMSP Database of Precipitating Auroral Electrons and Ions.

    PubMed

    Redmon, Robert J; Denig, William F; Kilcommons, Liam M; Knipp, Delores J

    2017-08-01

    Since the mid 1970's, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low earth orbit. As the program evolved, so to have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides. These are provided in a common and self-describing format that covers 30+ years of DMSP spacecraft from F06 (launched in 1982) through F18 (launched in 2009). This new database is accessible at the National Centers for Environmental Information (NCEI) and the Coordinated Data Analysis Web (CDAWeb). We describe how the new database is being applied to high latitude studies of: the co-location of kinetic and electromagnetic energy inputs, ionospheric conductivity variability, field aligned currents and auroral boundary identification. We anticipate that this new database will support a broad range of space science endeavors from single observatory studies to coordinated system science investigations.

  20. The auroral 6300 A emission - Observations and modeling

    NASA Technical Reports Server (NTRS)

    Solomon, Stanley C.; Hays, Paul B.; Abreu, Vincent J.

    1988-01-01

    A tomographic inversion is used to analyze measurements of the auroral atomic oxygen emission line at 6300 A made by the atmosphere explorer visible airglow experiment. A comparison is made between emission altitude profiles and the results from an electron transport and chemical reaction model. Measurements of the energetic electron flux, neutral composition, ion composition, and electron density are incorporated in the model.

  1. FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

    2002-01-01

    The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identity the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral SnapshoT (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data was used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and a long-system particle-in-cell simulation to model the magnetically connected region between the two satellites.

  2. Observation of subsecond variations in auroral region total electron content using 100 Hz sampling of GPS observables

    NASA Astrophysics Data System (ADS)

    McCaffrey, A. M.; Jayachandran, P. T.

    2017-06-01

    First ever auroral region total electron content (TEC) measurements at 100 Hz using a Septentrio PolaRxS Pro receiver are analyzed to discover ionospheric signatures which would otherwise be unobtainable with the frequently used lower sampling rates. Two types of variations are observed: small-magnitude (amplitude) variations, which are present consistently throughout the data set, and larger-magnitude (amplitude) variations, which are less frequent. Small-amplitude TEC fluctuations are accounted for by the receiver phase jitter. However, estimated secondary ionospheric effects in the calculation of TEC and the receiver phase jitter were unable to account for the larger-amplitude TEC fluctuations. These variations are also accompanied by fluctuations in the magnetic field, which seems to indicate that these fluctuations are real and of geophysical significance. This paper presents a technique and the capability of high-rate TEC measurements in the study of auroral dynamics. Further detailed study is needed to identify the cause of these subsecond TEC fluctuations and associated magnetic field fluctuations.

  3. Correlation Between Low Frequency Auroral Kilometric Radiation (AKR) and Auroral Structures

    NASA Technical Reports Server (NTRS)

    Paxamickas, Katherine A.; Green, James L.; Gallagher, Dennis L.; Boardsen, Scott; Mende, Stephen; Frey, Harald; Reinisch, Bodo W.

    2005-01-01

    Auroral Kilometric Radiation (AKR) is a radio wave emission that has long been associated with auroral activity. AKR is normally observed in the frequency range from -60 - 600 kHz. Low frequency AKR (or LF-AKR) events are characterized as a rapid extension of AKR related emissions to 30 kHz or lower in frequency for typically much less than 10 minutes. LF-AKR emissions predominantly occur within a frequency range of 20 kHz - 30 kHz, but there are LF-AKR related emissions that reach to a frequency of 5 kHz. This study correlates all instances of LF-AKR events during the first four years of observations from the IMAGE spacecraft's Radio Plasma Imager (WI) instrument with auroral observations from the wideband imaging camera (WIC) onboard IMAGE. The correlation between LF-AKR occurrence and WIC auroral observations shows that in the 295 confirmed cases of LF-AKR emissions, bifurcation of the aurora is seen in 74% of the cases. The bifurcation is seen in the dusk and midnight sectors of the auroral oval, where AKR is believed to be generated. The polarization of these LF-AKR emissions has yet to be identified. Although LF-AKR may not be the only phenomena correlated with bifurcated auroral structures, bifurcation will occur in most instances when LF-AKR is observed. The LF-AKR emissions may be an indicator of specific auroral processes sometimes occurring during storm-time conditions in which field-aligned density cavities extend a distance of perhaps 5-6 RE tailward from the Earth for a period of 10 minutes or less.

  4. Study on the parameters of the scanning system for the 300 keV electron accelerator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leo, K. W.; Chulan, R. M., E-mail: leo@nm.gov.my; Hashim, S. A.

    2016-01-22

    This paper describes the method to identify the magnetic coil parameters of the scanning system. This locally designed low energy electron accelerator with the present energy of 140 keV will be upgraded to 300 keV. In this accelerator, scanning system is required to deflect the energetic electron beam across a titanium foil in vertical and horizontal direction. The excitation current of the magnetic coil is determined by the energy of the electron beam. Therefore, the magnetic coil parameters must be identified to ensure the matching of the beam energy and excitation coil current. As the result, the essential parameters ofmore » the effective lengths for X-axis and Y-axis have been found as 0.1198 m and 0.1134 m and the required excitation coil currents which is dependenton the electron beam energies have be identified.« less

  5. The Electronic-Vibrational Behaviour of O2 in the Upper Atmosphere under Night-time Auroral Conditions

    NASA Astrophysics Data System (ADS)

    Jones, D. B.; Cartwright, D. C.; Campbell, L.; Teubner, P. J. O.; Brunger, M. J.; Bottema, M. J.

    2004-09-01

    We report on the extension of our Statistical Equlibrium Code (SEC) to determine the electronic-vibrational behaviour of O2 in the thermosphere, under night-time auroral conditions. This work was necessitated by the inadequacies in previous studies where the electron-impact cross section data bases employed have been superceeded, and/or direct excitation of states via electron impact has been neglected. Here we use the latest electron-impact cross section data bases to present the first electron-impact excitation rates for the 8 lowest lying electronic states of O_2. We then use these rates in conjunction with the most accurately available Franck-Condon factors, transition probabilities and quenching rates to determine the excited state populations. Note that predissociation, which is important for O_2, is also included in our model. We present radiative rates for various transitions and compare these results with those from other models and experimental rocket measurements.

  6. Feedback between neutral winds and auroral arc electrodynamics

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.; Walterscheid, R. L.

    1986-01-01

    The feedback between neutral atmospheric winds and the electrodynamics of a stable, discrete auroral arc is analyzed. The ionospheric current continuity equation and the equation for neutral gas acceleration by ion drag are solved simultaneously, as a function of time. The results show that, in general, the electric field in the ionosphere adjusts to neutral wind acceleration so as to keep auroral field-aligned currents and electron acceleration approximately independent of time. It is thus concluded that the neutral winds that develop as a result of the electrodynamical forcing associated with an arc do not significantly affect the intensity of the arc.

  7. First Observations of 5fce Auroral Roar Emissions

    NASA Astrophysics Data System (ADS)

    Labelle, J. W.

    2012-12-01

    Auroral radio emissions reveal physics of beam-plasma interactions and provide possibilities to remotely sense ionospheric plasma processes. Sato et al. [2012] recently discovered that auroral roar emissions, long known to occur at two and three times the electron gyrofrequency (fce), also occur at 4fce. Using data from wave receivers in the British Antarctic Survey Automatic Geophysical Observatories (BAS AGOs), we confirm the existence of 4fce-roars and observe for the first time 5fce-roars. A search at higher frequencies did not find higher harmonics, however. Both 4fce- and 5fce-roars only occur in sunlit conditions near the summer soltices. The harmonic emissions scale as expected with the strength of the geomagnetic field, and combining data from four stations with a wide range of magnetic field strengths suggests that the source height of the 4fce may lie around 245 km, significantly lower than the ˜ 275 km estimated for 2fce-roars. These observations show that the auroral roar generation mechanism acts under a broader set of plasma densities than previously considered, highlight how ubiquitous and robust the mechanism must be in different plasma environments, and suggest a broader application for remote sensing methods exploiting auroral roar, such as those described by Weatherwax et al. [2002]. References: Sato, Y., T. Ono, N. Sato, and Y. Ogawa, First observations of 4fce auroral roar emissions, Geophys. Res. Lett., 39, L07101, doi:10.1029/2012GL051205, 2012. Weatherwax, A.T., P.H. Yoon, and J. LaBelle, Model results and interpretation related to topside observations of auroral roar, J. Geophys. Res., 107, 10.1029/2001JA000315, 2002.

  8. QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tao, Jiawei; Wang, Linghua; Zong, Qiugang

    2016-03-20

    We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1–1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ∼0.1–1.5 keV to a Kappa distribution function with an index κ and effective temperature T{sub eff}. We also calculate the number density n and average energy E{sub avg} of strahl andmore » halo electrons by integrating the electron measurements between ∼0.1 and 1.5 keV. We find a strong positive correlation between κ and T{sub eff} for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity)« less

  9. Characteristics of dayside auroral displays in relation to magnetospheric processes

    NASA Astrophysics Data System (ADS)

    Minow, Joseph I.

    1997-09-01

    The use of dayside aurorae as a ground based monitor of magnetopause activity is explored in this thesis. The origin of diffuse (OI) 630.0 nm emissions in the midday auroral oval is considered first. Analysis of low altitude satellite records of precipitating charged particles within the cusp show an unstructured electron component that will produce a 0.5-1 kR 630.0 nm emission throughout the cusp. Distribution of the electrons is controlled by the requirement of charge neutrality in the cusp, predicting a diffuse 630.0 nm background even if the magnetosheath plasma is introduced into the magnetosphere in discrete merging events. Cusp electron fluxes also contain a structured component characterized by enhancements in the electron energy and energy flux over background values in narrow regions a few 10's of kilometers in width. These structured features are identified as the source of the transient midday arcs. An auroral model is developed to study the morphology of (OI) 630.0 nm auroral emissions produced by the transient arcs. The model demonstrates that a diffuse 630.0 nm background emission is produced by transient arcs due to the long lifetime of the O(1D) state. Two sources of diffuse 630.0 nm background emissions exist in the cusp which may originate in discrete merging events. The conclusion is that persistent 630.0 nm emissions cannot be interpreted as prima facie evidence for continuous particle transport from the magnetosheath across the magnetopause boundary and into the polar cusp. The second subject that is considered is the analysis of temporal and spatial variations of the diffuse 557.7 nm pulsating aurora in relation to the 630.0 nm dominated transient aurora. Temporal variations at the poleward boundary of the diffuse 557.7 nm aurora correlate with the formation of the 630.0 nm transient aurorae suggesting that the two events are related. The character of the auroral variations is consistent with the behavior of particle populations reported

  10. High latitude electromagnetic plasma wave emissions

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1983-01-01

    The principal types of electromagnetic plasma wave emission produced in the high latitude auroral regions are reviewed. Three types of radiation are described: auroral kilometric radiation, auroral hiss, and Z mode radiation. Auroral kilometric radiation is a very intense radio emission generated in the free space R-X mode by electrons associated with the formation of discrete auroral arcs in the local evening. Theories suggest that this radiation is an electron cyclotron resonance instability driven by an enhanced loss cone in the auroral acceleration region at altitudes of about 1 to 2 R sub E. Auroral hiss is a somewhat weaker whistler mode emission generated by low energy (100 eV to 10 keV) auroral electrons. The auroral hiss usually has a V shaped frequency time spectrum caused by a freqency dependent beaming of the whistler mode into a conical beam directed upward or downward along the magnetic field.

  11. Dayside auroral arcs and convection

    NASA Technical Reports Server (NTRS)

    Reiff, P. H.; Burch, J. L.; Heelis, R. A.

    1978-01-01

    Recent Defense Meteorological Satellite Program and International Satellite for Ionospheric Studies dayside auroral observations show two striking features: a lack of visible auroral arcs near noon and occasional fan shaped arcs radiating away from noon on both the morning and afternoon sides of the auroral oval. A simple model which includes these two features is developed by reference to the dayside convection pattern of Heelis et al. (1976). The model may be testable in the near future with simultaneous convection, current and auroral light data.

  12. The Consequences of Alfven Waves and Parallel Potential Drops in the Auroral Zone

    NASA Technical Reports Server (NTRS)

    Schriver, David

    2003-01-01

    The goal of this research is to examine the causes of field-aligned plasma acceleration in the auroral zone using satellite data and numerical simulations. A primary question to be addressed is what causes the field-aligned acceleration of electrons (leading to precipitation) and ions (leading to upwelling ions) in the auroral zone. Data from the Fast Auroral SnapshoT (FAST) and Polar satellites is used when the two satellites are in approximate magnetic conjunction and are in the auroral region. FAST is at relatively low altitudes and samples plasma in the midst of the auroral acceleration region while Polar is at much higher altitudes and can measure plasmas and waves propagating towards the Earth. Polar can determine the sources of energy streaming earthward from the magnetotail, either in the form of field-aligned currents, electromagnetic waves or kinetic particle energy, that ultimately leads to the acceleration of plasma in the auroral zone. After identifying and examining several events, numerical simulations are run that bridges the spatial region between the two satellites. The code is a one-dimensional, long system length particle in cell simulation that has been developed to model the auroral region. A main goal of this research project is to include Alfven waves in the simulation to examine how these waves can accelerate plasma in the auroral zone.

  13. Identifying the 630 nm auroral arc emission height: A comparison of the triangulation, FAC profile, and electron density methods

    NASA Astrophysics Data System (ADS)

    Megan Gillies, D.; Knudsen, D.; Donovan, E.; Jackel, B.; Gillies, R.; Spanswick, E.

    2017-08-01

    We present a comprehensive survey of 630 nm (red-line) emission discrete auroral arcs using the newly deployed Redline Emission Geospace Observatory. In this study we discuss the need for observations of 630 nm aurora and issues with the large-altitude range of the red-line aurora. We compare field-aligned currents (FACs) measured by the Swarm constellation of satellites with the location of 10 red-line (630 nm) auroral arcs observed by all-sky imagers (ASIs) and find that a characteristic emission height of 200 km applied to the ASI maps gives optimal agreement between the two observations. We also compare the new FAC method against the traditional triangulation method using pairs of all-sky imagers (ASIs), and against electron density profiles obtained from the Resolute Bay Incoherent Scatter Radar-Canadian radar, both of which are consistent with a characteristic emission height of 200 km.

  14. Magnetospheric and auroral plasmas: A short survey of progress, 1971 - 1975

    NASA Technical Reports Server (NTRS)

    Frank, L. A.

    1975-01-01

    Milestones in researches of auroral and magnetospheric plasmas for the past quadrennium 1971 - 1975 are reviewed. Findings, including those of the polar cusp, the polar wind, the explosive disruptions of the magnetotail, the interactions of hot plasmas with the plasmapause, the auroral field-aligned currents, and the striking 'inverted-V' electron precipitation events, are reported. Solutions to major questions concerning the origins and acceleration of these plasmas are discussed. A comprehensive bibliography of current research is included.

  15. Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere.

    PubMed

    Marklund, G T; Ivchenko, N; Karlsson, T; Fazakerley, A; Dunlop, M; Lindqvist, P A; Buchert, S; Owen, C; Taylor, M; Vaivalds, A; Carter, P; André, M; Balogh, A

    2001-12-13

    The bright night-time aurorae that are visible to the unaided eye are caused by electrons accelerated towards Earth by an upward-pointing electric field. On adjacent geomagnetic field lines the reverse process occurs: a downward-pointing electric field accelerates electrons away from Earth. Such magnetic-field-aligned electric fields in the collisionless plasma above the auroral ionosphere have been predicted, but how they could be maintained is still a matter for debate. The spatial and temporal behaviour of the electric fields-a knowledge of which is crucial to an understanding of their nature-cannot be resolved uniquely by single satellite measurements. Here we report on the first observations by a formation of identically instrumented satellites crossing a beam of upward-accelerated electrons. The structure of the electric potential accelerating the beam grew in magnitude and width for about 200 s, accompanied by a widening of the downward-current sheet, with the total current remaining constant. The 200-s timescale suggests that the evacuation of the electrons from the ionosphere contributes to the formation of the downward-pointing magnetic-field-aligned electric fields. This evolution implies a growing load in the downward leg of the current circuit, which may affect the visible discrete aurorae.

  16. Comment on "Pulsating Auroras Produced by Interactions of Electrons and Time Domain Structures" by Mozer Et Al.

    NASA Astrophysics Data System (ADS)

    Nishimura, Y.; Bortnik, J.; Li, W.; Angelopoulos, V.; Donovan, E. F.; Spanswick, E. L.

    2018-03-01

    Mozer et al. (2017, https://doi.org/10.1002/2017JA024223) suggested that time domain structures (TDSs) drive pulsating aurora (with additional contributions by kinetic Alfvén waves (KAWs)) and that chorus waves have negligible effects. In this comment, we point out that electrons scattered by TDS or KAW (dominantly at 0.1-3 keV, <1 s modulation) cannot explain key features of pulsating aurora, which require precipitation above a few keV with a couple of tens of second modulation. Their study did not conduct quantitative evaluations of wave-aurora correlation. The use of short burst mode data ( <10 s) may only cover a single pulse of pulsating aurora and is not suitable for examining connections to pulsating aurora. "Field-aligned" electrons do not necessarily represent loss cone population, and their characteristic energy (hundreds of eV) is much lower than typical precipitation over pulsating aurora. By reexamining the events studied by Mozer et al., we quantitatively demonstrate that TDS and KAW are uncorrelated with pulsating aurora and that only chorus waves showed high correlations with pulsating aurora. Occasional simultaneous occurrence of TDS/KAW and pulsating aurora is found to be coincidental, because the correlation over a time scale of minutes is poor. Several auroral features analyzed in that paper are not pulsating aurora but other types of aurora. We also show that the chorus-pulsating aurora correlation can last for 2 h or longer and can be used to highlight dynamic changes in magnetic field mapping. Chorus waves can resonate with electrons above a few keV and are in agreement with pulsating auroral properties.

  17. Jupiter's Auroral Energy Input Observed by Hisaki/EXCEED and its Modulations by Io's Volcanic Activity

    NASA Astrophysics Data System (ADS)

    Tao, C.; Kimura, T.; Tsuchiya, F.; Murakami, G.; Yoshioka, K.; Kita, H.; Yamazaki, A.; Kasaba, Y.; Yoshikawa, I.; Fujimoto, M.

    2016-12-01

    Aurora is an important indicator representing the momentum transfer from the fast-rotating outer planet to the magnetosphere and the energy input into the atmosphere through the magnetosphere-ionosphere coupling. Long-term monitoring of Jupiter's northern aurora was achieved by the Extreme Ultraviolet (EUV) spectrometer called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) onboard JAXA's Earth-orbiting planetary space telescope Hisaki until today after its launch in September 2013. We have proceeded the statistical survey of the Jupiter's auroral energy input into the upper atmosphere. The auroral electron energy is estimated using a hydrocarbon color ratio (CR) adopted for the wavelength range of EXCEED, and the emission power in the long wavelength range 138.5-144.8 nm is used as an indicator of total emitted power before hydrocarbon absorption and auroral electron energy flux. Temporal dynamic variation of the auroral intensity was detected when Io's volcanic activity and thus EUV emission from the Io plasma torus are enhanced in the early 2015. Average of the total input power over 80 days increases by 10% with sometimes sporadically more than a factor of 3 upto 7, while the CR indicates the auroral electron energy decrease by 20% during the volcanic event compared to the other period. This indicates much more increase in the current system and Joule heating which contributes heating of the upper atmosphere. We will discuss the impact of this event on the upper atmosphere and ionosphere.

  18. AURORAL X-RAYS, COSMIC RAYS, AND RELATED PHENOMENA DURING THE STORM OF FEBRUARY 10-11, 1958

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Winckler, J.R.; Peterson, L.; Hoffman, R.

    1959-06-01

    Balloon observations were made during the auroral storm of February 10- 11, 1958, at Minneapolis. Strong x-ray bursts in two groups were detected. The groups appeared coincident with two large magnetic bays, with strong radio noise absorption, and with the passage across the zenith of a very large amount of auroral luminosity. From the x-ray intensity and measured energies, an electron current of 0.6 x 10/sup 6/ electrons /cm/sup 2// scc was present. These electrons ionizing the upper D layer accounted for the increased cosmic noise absorption. The x-rays themselves carried 1000 times less energy than the electrons and couldmore » not provide sufficient ionization for the observed radio absorption. Visual auroral fornis during this storm are reported to have lower borders at thc 200 to 300 km level. There is thus a difficulty in bringing the electrons to the D layer without ani accompanying visible aurora. A cosmic-ray decrease accompanied the storm and was observed to be from 4 to 6% at sea level, 21% in the balloon altitude ionization, and 15% in total energy influx at 55 deg geomagnetic latitude. Compared with the great intensity of the magnetic and auroral phenomena in this storm, the cosmic-ray modulation was not exceptionally large. (auth)« less

  19. An auroral oval at the footprint of Saturn's kilometric radio sources, colocated with the UV aurorae

    NASA Astrophysics Data System (ADS)

    Lamy, L.; Cecconi, B.; Prangé, R.; Zarka, P.; Nichols, J. D.; Clarke, J. T.

    2009-10-01

    Similarly to other magnetized planets, Saturn displays auroral emissions generated by accelerated electrons gyrating around high-latitude magnetic field lines. They mainly divide in ultraviolet (UV) and infrared (IR) aurorae, excited by electron collisions with the upper atmosphere, and Saturn's kilometric radiation (SKR), radiated from higher altitudes by electron-wave resonance. Whereas spatially resolved UV and IR images of atmospheric aurorae reveal a continuous auroral oval around each pole, the SKR source locus was only indirectly constrained by the Voyager radio experiment to a limited local time (LT) range on the morningside, leading to interpretation of the SKR modulation as a fixed flashing light. Here, we present resolved SKR maps derived from the Cassini Radio and Plasma Wave Science (RPWS) experiment using goniopolarimetric techniques. We observe radio sources all around the planet, organized along a high-latitude continuous auroral oval. Observations of the Hubble Space Telescope obtained in January 2004 and January 2007 have been compared to simultaneous and averaged Cassini-RPWS measurements, revealing that SKR and UV auroral ovals are very similar, both significantly enhanced on the dawnside. These results imply that the SKR and atmospheric aurorae are triggered by the same populations of energetic electron beams, requiring a unified model of particle acceleration and precipitation on Saturn.

  20. Solar Wind 0.1-1 keV Electrons in the Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Wang, L.; Tao, J.; Li, G.; Wimmer-Schweingruber, R. F.; Jian, L. K.; He, J.; Tu, C.; Tian, H.; Bale, S. D.

    2017-12-01

    Here we present a statistical study of the 0.1-1 keV suprathermal electrons in the undisturbed and compressed slow/fast solar wind, for the 71 corotating interaction regions (CIRs) with good measurements from the WIND 3DP and MFI instruments from 1995 to 1997. For each of these CIRs, we separate the strahl and halo electrons based on their different behaviors in pitch angle distributions in the undisturbed and compressed solar wind. We fit both the strahl and halo energy spectra to a kappa function with an index κ index and effective temperature Teff, and calculate the pitch-angle width at half-maximum (PAHM) of the strahl population. We also integrate the electron measurements between 0.1 and 1.0 keV to obtain the number density n and average energy Eavg for the strahl and halo populations. We find that for both the strahl and halo populations within and around these CIRs, the fitted κ index strongly correlates with Teff, similar to the quiet-time solar wind (Tao et al., ApJ, 2016). The number density of both the strahl and halo shows a strong positive correlation with the electron core temperature. The strahl number density ns is correlated with the magnitude of interplanetary magnetic field, and the strahl PAHM width is anti-correlated with the solar wind speed. These results suggest that the origin of strahl electrons from the solar corona is likely related to the electron core temperature and magnetic field strength, while the production of halo electrons in the interplanetary medium could depend on the solar wind velocity.

  1. Dawn Auroral Breakup at Saturn Initiated by Auroral Arcs: UVIS/Cassini Beginning of Grand Finale Phase

    NASA Astrophysics Data System (ADS)

    Radioti, A.; Grodent, D.; Yao, Z. H.; Gérard, J.-C.; Badman, S. V.; Pryor, W.; Bonfond, B.

    2017-12-01

    We present Cassini auroral observations obtained on 11 November 2016 with the Ultraviolet Imaging Spectrograph at the beginning of the F-ring orbits and the Grand Finale phase of the mission. The spacecraft made a close approach to Saturn's southern pole and offered a remarkable view of the dayside and nightside aurora. With this sequence we identify, for the first time, the presence of dusk/midnight arcs, which are azimuthally spread from high to low latitudes, suggesting that their source region extends from the outer to middle/inner magnetosphere. The observed arcs could be auroral manifestations of plasma flows propagating toward the planet from the magnetotail, similar to terrestrial "auroral streamers." During the sequence the dawn auroral region brightens and expands poleward. We suggest that the dawn auroral breakup results from a combination of plasma instability and global-scale magnetic field reconfiguration, which is initiated by plasma flows propagating toward the planet. Alternatively, the dawn auroral enhancement could be triggered by tail magnetic reconnection.

  2. Stagnation of Saturn's auroral emission at noon

    NASA Astrophysics Data System (ADS)

    Radioti, A.; Grodent, D.; Gérard, J.-C.; Southwood, D. J.; Chané, E.; Bonfond, B.; Pryor, W.

    2017-06-01

    Auroral emissions serve as a powerful tool to investigate the magnetospheric processes at Saturn. Solar wind and internally driven processes largely control Saturn's auroral morphology. The main auroral emission at Saturn is suggested to be connected with the magnetosphere-solar wind interaction, through the flow shear related to rotational dynamics. Dawn auroral enhancements are associated with intense field-aligned currents generated by hot tenuous plasma carried toward the planet in fast moving flux tubes as they return from tail reconnection site to the dayside. In this work we demonstrate, based on Cassini auroral observations, that the main auroral emission at Saturn, as it rotates from midnight to dusk via noon, occasionally stagnates near noon over a couple of hours. In half of the sequences examined, the auroral emission is blocked close to noon, while in three out of four cases, the blockage of the auroral emission is accompanied with signatures of dayside reconnection. We discuss some possible interpretations of the auroral "blockage" near noon. According to the first one, it could be related to local time variations of the flow shear close to noon. Auroral local time variations are also suggested to be initiated by radial transport process. Alternatively, the auroral blockage at noon could be associated with a plasma circulation theory, according to which tenuously populated closed flux tubes as they return from the nightside to the morning sector experience a blockage in the equatorial plane and they cannot rotate beyond noon.

  3. Calculations of stopping powers of 100 eV-30 keV electrons in 31 elemental solids

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tanuma, S.; Powell, C. J.; Penn, D. R.

    We present calculated electron stopping powers (SPs) for 31 elemental solids (Li, Be, glassy C, graphite, diamond, Na, Mg, K, Sc, Ti, V, Fe, Y, Zr, Nb, Mo, Ru, Rh, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, and Bi). These SPs were determined with an algorithm previously used for the calculation of electron inelastic mean free paths and from energy-loss functions (ELFs) derived from experimental optical data. The SP calculations were made for electron energies between 100 eV and 30 keV and supplement our earlier SP calculations for ten additional solids (Al, Si, Cr, Ni,more » Cu, Ge, Pd, Ag, Pt, and Au). Plots of SP versus atomic number for the group of 41 solids show clear trends. Multiple peaks and shoulders are seen that result from the contributions of valence-electron and various inner-shell excitations. Satisfactory agreement was found between the calculated SPs and values from the relativistic Bethe SP equation with recommended values of the mean excitation energy (MEE) for energies above 10 keV. We determined effective MEEs versus maximum excitation energy from the ELFs for each solid. Plots of effective MEE versus atomic number showed the relative contributions of valence-electron and different core-electron excitations to the MEE. For a maximum excitation energy of 30 keV, our effective MEEs agreed well for Be, graphite, Na, Al, and Si with recommended MEEs; a difference for Li was attributed to sample oxidation in the SP measurements for the recommended MEE. Substantially different effective MEEs were found for the three carbon allotropes (graphite, diamond, and glassy C)« less

  4. STABILITY OF EXTRATERRESTRIAL GLYCINE UNDER ENERGETIC PARTICLE RADIATION ESTIMATED FROM 2 keV ELECTRON BOMBARDMENT EXPERIMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maté, B.; Tanarro, I.; Escribano, R.

    2015-06-20

    The destruction of solid glycine under irradiation with 2 keV electrons has been investigated by means of IR spectroscopy. Destruction cross sections, radiolysis yields, and half-life doses were determined for samples at 20, 40, 90, and 300 K. The thickness of the irradiated samples was kept below the estimated penetration depth of the electrons. No significant differences were obtained in the experiments below 90 K, but the destruction cross section at 300 K was larger by a factor of 2. The radiolysis yields and half-life doses are in good accordance with recent MeV proton experiments, which confirms that electrons inmore » the keV range can be used to simulate the effects of cosmic rays if the whole sample is effectively irradiated. In the low temperature experiments, electron irradiation leads to the formation of residues. IR absorptions of these residues are assigned to the presence CO{sub 2}, CO, OCN{sup −}, and CN{sup −} and possibly to amide bands I to III. The protection of glycine by water ice is also studied. A water ice film of ∼150 nm is found to provide efficient shielding against the bombardment of 2 keV electrons. The results of this study show also that current Monte Carlo predictions provide a good global description of electron penetration depths. The lifetimes estimated in this work for various environments ranging from the diffuse interstellar medium to the inner solar system, show that the survival of hypothetical primeval glycine from the solar nebula in present solar system bodies is not very likely.« less

  5. DMSP Spacecraft Charging in Auroral Environments

    NASA Technical Reports Server (NTRS)

    Colson, Andrew; Minow, Joseph

    2011-01-01

    The Defense Meteorological Satellite Program (DMSP) spacecraft are a series of low-earth orbit (LEO) satellites whose mission is to observe the space environment using the precipitating energetic particle spectrometer (SSJ/4-5). DMSP satellites fly in a geosynchronous orbit at approx.840 km altitude which passes through Earth s ionosphere. The ionosphere is a region of partially ionized gas (plasma) formed by the photoionization of neutral atoms and molecules in the upper atmosphere of Earth. For satellites in LEO, such as DMSP, the plasma density is usually high and the main contributors to the currents to the spacecraft are the precipitating auroral electrons and ions from the magnetosphere as well as the cold plasma that constitutes the ionosphere. It is important to understand how the ionosphere and auroral electrons can accumulate surface charges on satellites because spacecraft charging has been the cause of a number of significant anomalies for on-board instrumentation on high altitude spacecraft. These range from limiting the sensitivity of measurements to instrument malfunction depending on the magnitude of the potential difference over the spacecraft surface. Interactive Data Language (IDL) software was developed to process SSJ/4-5 electron and ion data and to create a spectrogram of the particles number and energy fluxes. The purpose of this study is to identify DMSP spacecraft charging events and to present a preliminary statistical analysis. Nomenclature

  6. APES: Acute Precipitating Electron Spectrometer - A High Time Resolution Monodirectional Magnetic Deflection Electron Spectrometer

    NASA Technical Reports Server (NTRS)

    Michell, R. G.; Samara, M.; Grubbs, G., II; Ogasawara, K.; Miller, G.; Trevino, J. A.; Webster, J.; Stange, J.

    2016-01-01

    We present a description of the Acute Precipitating Electron Spectrometer (APES) that was designed and built for the Ground-to-Rocket Electron Electrodynamics Correlative Experiment (GREECE) auroral sounding rocket mission. The purpose was to measure the precipitating electron spectrum with high time resolution, on the order of milliseconds. The trade-off made in order to achieve high time resolution was to limit the aperture to only one look direction. The energy selection was done by using a permanent magnet to separate the incoming electrons, such that the different energies would fall onto different regions of the microchannel plate and therefore be detected by different anodes. A rectangular microchannel plate (MCP) was used (15 mm x 100 mm), and there was a total of 50 discrete anodes under the MCP, each one 15 mm x 1.5 mm, with a 0.5 mm spacing between anodes. The target energy range of APES was 200 eV to 30 keV.

  7. Low noise scintillation detectors with a P-47 thin layer screen for electrons of several keV

    NASA Astrophysics Data System (ADS)

    Kajcsos, Zs.; Meisel, W.; Griesbach, P.; Gütlich, P.; Sauer, Ch.; Kurz, R.; Hildebrand, K.; Albrecht, R.; Ligtenberg, M. A. C.

    1994-09-01

    The applicability of a low-noise scintillation detector (ScD) for the registration of electrons of several keV energy has been studied employing photomultipliers (PM) of different types and sizes. With the application of a sedimented P-47 scintillation screen, the values of the low-energy sensitivity limit and those of the light conversion coefficient were determined as about 2.7-4.7 keV and 2.8-6.6 photoelectrons/keV, respectively, for the set of PM's (Philips-Valvo XP 2020, Philips-Valvo XP 2052, Philips-Valvo XP 2972, EMI 9124a) studied. It is concluded that such scintillation detectors might be used advantageously as electron counters in the range of E > 5 keV. Applications below this kinetic energy value are also feasible when applying a floating acceleration of several kV to the ScD — a voltage much lower than the values required for Everhart-Thornley detectors.

  8. Two-dimensional quasi-neutral description of particles and fields above discrete auroral arcs

    NASA Technical Reports Server (NTRS)

    Newman, A. L.; Chiu, Y. T.; Cornwall, J. M.

    1986-01-01

    Models are presented for particle distributions, electric fields and currents in an adiabatic treatment of auroral electrostatic potential distributions in order to describe the quiet-time evening auroral arcs featuring both upward and return currents. The models are consistent with current continuity and charge balance requirements for particle populations controlled by adiabatic invariants and quasi-neutrality in the magnetosphere. The effective energy of the cool electron population is demonstrated to have a significant effect on the latitudinal breadth of the auroral electrostatic potential structure and the extent of the penetration of the accelerating potential into the ionosphere. Another finding is that the energy of any parallel potential drop in the lowest few thousand kilometers of the field line is of the same order of magnitude as the thermal energy of the cool electrons. Additional predictions include density cavities along field lines that support large potential drops, and density enhancements along field lines at the edge of an inverted V with a small potential drop.

  9. Thermoluminescent response of LiF:Mg,Ti to 20 keV electrons.

    PubMed

    Mercado-Uribe, H; Brandan, M E

    2002-01-01

    The thermoluminescence response of LiF:Mg,Ti (TLD-100) to 20 keV electrons from a scanning electron microscope has been measured. Radiochromic dye films previously calibrated were used to determine the fluence incident on TLD-100 chips. The procedure for irradiation and glow curve deconvolution was adhered to the protocols previously determined in our laboratory for gamma rays and heavy charged particles. The response at electron fluences higher than 4 x 10(10) cm(-2) is supralinear, due to the increasingly relevant contribution of the high temperature peaks. The relative contribution of the high temperature peaks to the TL signal is abnormally small, about half that observed in gamma irradiation and four times smaller than what has been measured in low-energy X ray exposure.

  10. Jovian longitudinal asymmetry in Io-related and Europa-related auroral hot spots

    NASA Technical Reports Server (NTRS)

    Dessler, A. J.; Chamberlain, J. W.

    1979-01-01

    Auroral emissions generated by the Jovian moons Io and Europa, originating at the foot of the magnetic flux tubes of the satellites, may be largely limited to longitudes where the planet's ionospheric conductivity is enhanced. The enhanced conductivity is produced by trapped energetic electrons that drift into the Jovian atmosphere in regions where the planet's magnetic field is anomalously weak. The most active auroral hot-spot emissions lie in a sector of the northern hemisphere defined by decametric radio emission. Weaker auroral hot spots are found in the southern hemisphere along a magnetic conjugate trace. The brightness and the longitude of the Jovian hot spots predicted in this paper are in agreement with observations reported by Atreya et al. (1977).

  11. From discrete auroral arcs to the magnetospheric generator: numerical model and case study

    NASA Astrophysics Data System (ADS)

    Lamy, H.; Echim, M.; Cessateur, G.; Simon Wedlund, C.; Gustavsson, B.; Maggiolo, R.; Gunell, H.; Darrouzet, F.; De Keyser, J.

    2017-12-01

    We discuss an analysis method developed to estimate some of the properties of auroral generators (electron density, ne and temperature, Te), from ionospheric observations of the energy flux of precipitating electrons, e, measured across an auroral arc. The method makes use of a quasi-static magnetosphere-ionosphere coupling model. Assuming that the generator is a magnetospheric plasma interface, one obtains a parametric description of the generator electric field as a function of the kinetic and MHD properties of the interface. This description of the generator is introduced in a stationary M-I coupling model based on the current continuity in the topside ionosphere (Echim et al, 2007). The model is run iteratively for typical values of the magnetospheric ne and Te that are adjusted until the precipitating energy flux ɛ provided by the model at ionospheric altitudes fits the observations. The latter can be provided either in-situ by spacecraft measurements or remotely from optical ground-based observations. The method is illustrated by using the precipitating energy flux observed in-situ by DMSP on April 28, 2001, above a discrete auroral arc. For this particular date we have been able to compare the generator properties determined with our method with actual magnetospheric in-situ data provided by Cluster. The results compare very well and hence validate the method. The methodology is then applied on the energy flux of precipitating electrons estimated from optical images of a discrete auroral arc obtained simultaneously with the CCD cameras of the ALIS (Auroral Large Imaging System) network located in Scandinavia on 5 March 2008 (Simon Wedlund et al, 2013). Tomography-like techniques are used to retrieve the three-dimensional volume emission rates at 4278 Å from which the energy spectra of precipitating magnetospheric electrons can be further derived. These spectra are obtained along and across the arc, with a spatial resolution of approximately 3 km and

  12. Scientific interpretation of historical auroral records

    NASA Astrophysics Data System (ADS)

    Willis, D. M.; Stephenson, F. R.

    The available historical auroral records from both Europe and East Asia are examined critically for their relevance in the investigation of long-term variations in both solar activity and the Earth's magnetic field. The early oriental records are sufficiently numerous to allow scientific studies of variations on several time scales. Special attention is paid to the seasonal and secular variations of the early oriental auroral observations. In addition, the oriental auroral records exhibit a clear 27-day recurrence tendency at particular periods of time. A search has been made for examples of strictly simultaneous and indisputably independent observations of the aurora from spatially separated sites in East Asia. This search has yielded nine observations of mid-latitude auroral displays at more than one site in East Asia on the same night. A particular geomagnetic storm that occurred during December in AD 1128 is investigated in detail. Five days after the observation of two large sunspots in England, a red auroral display was observed from Korea. In addition, between the middle of AD 1127 and the middle of AD 1129, five Chinese and five Korean auroral observations were recorded. These provide evidence for recurrent auroral activity on a timescale almost exactly equal to the synodic-solar-rotation period (approximately 27 days). Finally, a new attempt is made to use the oriental historical auroral records to determine the location of the north geomagnetic pole during the European Middle Ages.

  13. Surface Charging in the Auroral Zone on the DMSP Spacecraft in LEO

    NASA Astrophysics Data System (ADS)

    Anderson, Phillip C.

    1998-11-01

    A recent anomaly on the DMSP F13 spacecraft was attributed to an electrical malfunction caused by an electrostatic discharge on the vehicle associated with surface charging. It occurred during an intense energetic electron precipitation event (an auroral arc) within a region of very low plasma density in the auroral zone. A study of 1.5 year's worth of DMSP data from three satellites acquired during the recent minimum in the solar cycle has shown that such charging was a common occurrence with 704 charging events found. This is the result of significantly reduced background plasma densities associated with the solar minimum; smaller than ever previously experienced by the DMSP spacecraft. At times, the spacecraft charged for periods of 10s of seconds as they skimmed along an auroral arc instead of cutting across it. We show examples of the observed plasma density and the precipitating electron and ion spectra associated with the charging, and the MLT distribution and the seasonal distribution of the events. The preponderance of events occurred in the premidnight and morning sectors with two types of electron spectra being observed: a sharply peaked distribution indicative of field-aligned acceleration in the premidnight sector and a very hard distribution in the morning sector.

  14. A new DMSP magnetometer and auroral boundary data set and estimates of field-aligned currents in dynamic auroral boundary coordinates

    NASA Astrophysics Data System (ADS)

    Kilcommons, Liam M.; Redmon, Robert J.; Knipp, Delores J.

    2017-08-01

    We have developed a method for reprocessing the multidecadal, multispacecraft Defense Meteorological Satellite Program Special Sensor Magnetometer (DMSP SSM) data set and have applied it to 15 spacecraft years of data (DMSP Flight 16-18, 2010-2014). This Level-2 data set improves on other available SSM data sets with recalculated spacecraft locations and magnetic perturbations, artifact signal removal, representations of the observations in geomagnetic coordinates, and in situ auroral boundaries. Spacecraft locations have been recalculated using ground-tracking information. Magnetic perturbations (measured field minus modeled main field) are recomputed. The updated locations ensure the appropriate model field is used. We characterize and remove a slow-varying signal in the magnetic field measurements. This signal is a combination of ring current and measurement artifacts. A final artifact remains after processing: step discontinuities in the baseline caused by activation/deactivation of spacecraft electronics. Using coincident data from the DMSP precipitating electrons and ions instrument (SSJ4/5), we detect the in situ auroral boundaries with an improvement to the Redmon et al. (2010) algorithm. We embed the location of the aurora and an accompanying figure of merit in the Level-2 SSM data product. Finally, we demonstrate the potential of this new data set by estimating field-aligned current (FAC) density using the Minimum Variance Analysis technique. The FAC estimates are then expressed in dynamic auroral boundary coordinates using the SSJ-derived boundaries, demonstrating a dawn-dusk asymmetry in average FAC location relative to the equatorward edge of the aurora. The new SSM data set is now available in several public repositories.

  15. Understanding the Origin of Jupiter's Diffuse Aurora Using Juno's First Perijove Observations

    NASA Astrophysics Data System (ADS)

    Li, W.; Thorne, R. M.; Ma, Q.; Zhang, X.-J.; Gladstone, G. R.; Hue, V.; Valek, P. W.; Allegrini, F.; Mauk, B. H.; Clark, G.; Kurth, W. S.; Hospodarsky, G. B.; Connerney, J. E. P.; Bolton, S. J.

    2017-10-01

    Juno observed the low-altitude polar region during perijove 1 on 27 August 2016 for the first time. Auroral intensity and false-color maps from the Ultraviolet Spectrograph (UVS) instrument show extensive diffuse aurora observed equatorward of the main auroral oval. Juno passed over the diffuse auroral region near the System III longitude of 120°-150° (90°-120°) in the northern (southern) hemisphere. In the region where these diffuse auroral emissions were observed, the Jupiter Energetic Particle Detector Instrument (JEDI) and Jovian Auroral Distributions Experiment (JADE) instruments measured nearly full loss cone distributions for the downward going electrons over energies of 0.1-700 keV but very few upward going electrons. The false-color maps from UVS indicate more energetic electron precipitation at lower latitudes than less energetic electron precipitation, consistent with observations of precipitating electrons measured by JEDI and JADE. The comparison between particle and aurora measurements provides first direct evidence that these precipitating energetic electrons are mainly responsible for the diffuse auroral emissions at Jupiter.

  16. Simultaneous measurements of auroral particles and electric currents by a rocket-borne instrument system - Introductory remarks

    NASA Technical Reports Server (NTRS)

    Anderson, H. R.; Cloutier, P. A.

    1975-01-01

    A rocket-borne experiment package has been designed to obtain simultaneous in situ measurements of the pitch angle distributions and energy spectra of primary auroral particles, the flux of neutral hydrogen at auroral energies, the electric currents flowing in the vicinity of the auroral arc as determined from vector magnetic data, and the modulation of precipitating electrons in the frequency range 0.5-10 MHz. The experiment package was launched by a Nike-Tomahawk rocket from Poker Flat, Alaska, at 0722 UT on Feb. 25, 1972, over a bright auroral band. This paper is intended to serve as an introduction to the detailed discussion of results given in the companion papers. As such it includes a brief review of the general problem, a discussion of the rocket instrumentation, a delineation of the auroral and geomagnetic conditions at the time of launch, and comments on the overall payload performance.

  17. Testing the Auroral Current-Voltage Relation in Multiple Arcs

    NASA Astrophysics Data System (ADS)

    Cameron, T. G.; Knudsen, D. J.; Cully, C. M.

    2013-12-01

    The well-known current-voltage relation within auroral inverted-V regions [Knight, Planet. Space Sci., 21, 741, 1973] predicts current carried by an auroral flux tube given the total potential drop between a plasma-sheet source region and the ionosphere. Numerous previous studies have tested this relation using spacecraft that traverse auroral arcs at low (ionospheric) or mid altitudes. Typically, the potential drop is estimated at the peak of the inverted-V, and field-aligned current is estimated from magnetometer data; statistical information is then gathered over many arc crossings that occur over a wide range of source conditions. In this study we use electron data from the FAST satellite to examine the current-voltage relation in multiple arc sets, in which the key source parameters (plasma sheet density and temperature) are presumed to be identical. We argue that this approach provides a more sensitive test of the Knight relation, and we seek to explain remaining variability with factors other than source variability. This study is supported by a grant from the Natural Sciences and Engineering Research Council of Canada.

  18. Van Allen Probe measurements of intense Poynting Flux, magnetic dipolarization, and particle energization and auroral arcs.

    NASA Astrophysics Data System (ADS)

    Wygant, J. R.; Tian, S.; Thaller, S. A.; Breneman, A. W.; Cattell, C. A.; Engel, A.; Mozer, F.; Bonnell, J. W.; Chaston, C. C.; Donovan, E.; Spanswick, E.; Reeves, G.; Kistler, L. M.; Mouikis, C.; Hudson, M.; Smith, C. W.; Fennell, J. F.; Blake, J. B.; Turner, D. L.; Baker, D. N.; Kletzing, C.

    2017-12-01

    In recent years, there has been a focus on measurements in the near Earth plasmasheet of intervals of intense parallel Poynting flux, magnetic dipolarizations, and energetic particle injection/ and acceleration, as well as, ion ouflow from low altitudes (Ergun et al., 2015; Wygant et al., 2015 and Tian et. al. this meeting). We describe observations from an event on 5/1/2013 and related events on 6/01/2013 and 4/14/2013. Measurements from Van Allen Probes demonstrate that intrinsic to the structure of these dipolarization events are intense pulses (>100 mW/m2) of Poynting flux lasting 1 minute at the leading edge of the dipolarization front. The electric field associated with the Poynting flux burst is primarily in the poloidal direction (70 mV/m) but does also have a significant azimuthal (dawn-dusk) component of 20 mV/m capable of injecting electrons earthward and energizing them via conservation of the first adiabatic invariant. The THEMIS auroral array is used to show that these intervals of Poynting flux are nearly exactly coincident with thin (30 km wide) intense auroral arcs, which also have durations comparable to the Poynting flux. The correspondence between the arc and the Poynting flux allows us to infer the spatial dimensions of the electric fields, which might accelerate particles. Based on the dimensions of the arc, we estimate that at the spacecraft, the region of strong electric field is 1- 1.5 Re in azimuthal extent and 600- 900 km in poloidal direction. The associated EMF along the longitudinal direction is 150-200 kilovolts while the EMF in the poloidal direction is 30-60 kilovolts.Van Allen Probe measurements show that there are abrupt peaks in energetic electrons between 30 keV to 2 MeV coincident with these fields.The enhancements are dispersion-less locally but show energy-time dispersion as seen by LANL spacecraft displaced in MLT. Subsequent to the initial pulse of Poynting flux, there is a longer term (5-30 minutes) second phase of the

  19. Acceleration of electrons in strong beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

    1984-01-01

    The effects of strong beam-plasma interactions on the electron population of the upper atmosphere have been investigated in an electron acceleration experiment performed with a sounding rocket. The rocket carried the Several Complex Experiments (SCEX) payload which included an electron accelerator, three disposable 'throwaway' detectors (TADs), and a stepped electron energy analyzer. The payload was launched in an auroral arc over the rocket at altitudes of 157 and 178 km, respectively. The performance characteristics of the instruments are discussed in detail. The data are combined with the results of laboratory measurements and show that electrons with energies of at least two and probably four times the injection energy of 2 keV were observed during strong beam-plasma interaction events. The interaction events occurred at pitch angles of 54 and 126 degrees. On the basis of the data it is proposed that the superenergization of the electrons is correlated with the length of the beam-plasma interaction region.

  20. Silicon-carbon bond inversions driven by 60-keV electrons in graphene.

    PubMed

    Susi, Toma; Kotakoski, Jani; Kepaptsoglou, Demie; Mangler, Clemens; Lovejoy, Tracy C; Krivanek, Ondrej L; Zan, Recep; Bangert, Ursel; Ayala, Paola; Meyer, Jannik C; Ramasse, Quentin

    2014-09-12

    We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of nondestructive and atomically precise structural modification and detection for two-dimensional materials.

  1. 3D model of auroral emissions for Europa

    NASA Astrophysics Data System (ADS)

    Cessateur, G.; Barthelemy, M.; Rubin, M.; Lilensten, J.; Maggiolo, R.; De Keyser, J.; Gunell, H.; Loreau, J.

    2017-12-01

    As archetype of icy satellites, Europa will be one of the primary targets of the ESA JUICE and NASA Europa Clipper missions. Through surface sputtering, Europa does possess a thin neutral gas atmosphere, mainly composed of O2 and H2O. Valuable information can therefore be retrieved from auroral and airglow measurements. We present here a 3D electron-excitation-transport-emission coupled model of oxygen line emissions produced through precipitating electrons. The density and temperature of the electrons are first derived from the multifluid MHD model from Rubin et al. (2015). Oxygen emission lines in the UV have first been modelled, such as those at 130.5 and 135.6 nm, and there is a nonhomogenous distribution of the emission. For 135.6 nm, the line emission can be significant and reach 700 Rayleigh close to the surface for a polar limb viewing angle. Visible emissions with the red-doublet (630-636.4 nm) and green (577.7 nm) oxygen lines are also considered with emission intensities reaching 7150 R and 200 R, respectively, for limb polar viewing. Using different cross section data, a sensitivity study has also been performed to assess the impact of the uncertainties on the auroral emissions.

  2. Electrodynamic parameters in the nighttime sector during auroral substorms

    NASA Technical Reports Server (NTRS)

    Fujii, R.; Hoffman, R. A.; Anderson, P. C.; Craven, J. D.; Sugiura, M.; Frank, L. A.; Maynard, N. C.

    1994-01-01

    The characteristics of the large-scale electrodynamic parameters, field-aligned currents (FACs), electric fields, and electron precipitation, which are associated with auroral substorm events in the nighttime sector, have been obtained through a unique analysis which places the ionospheric measurements of these parameters into the context of a generic substorm determined from global auroral images. A generic bulge-type auroral emission region has been deduced from auroral images taken by the Dynamics Explorer 1 (DE 1) satellite during a number of isolated substorms, and the form has been divided into six sectors, based on the peculiar emission characteristics in each sector: west of bulge, surge horn, surge, middle surge, eastern bulge, and east of bulge. By comparing the location of passes of the Dynamics Explorer 2 (DE 2) satellite to the simultaneously obtained auroral images, each pass is placed onto the generic aurora. The organization of DE 2 data in this way has systematically clarified peculiar characteristics in the electrodynamic parameters. An upward net current mainly appears in the surge, with little net current in the surge horn and the west of bulge. The downward net current is distributed over wide longitudinal regions from the eastern bulge to the east of bulge. Near the poleward boundary of the expanding auroral bulge, a pair of oppositely directed FAC sheets is observed, with the downward FAC on the poleward side. This downward FAC and most of the upward FAC in the surge and the middle surge are assoc iated with narrow, intense antisunwqard convection, corresponding to an equatorward directed spikelike electric field. This pair of currents decreases in amplitude and latitudinal width toward dusk in the surge and the west of bulge, and the region 1 and 2 FACs become embedded in the sunward convection region. The upward FAC region associated with the spikelike field on the poleward edge of the bulge coincides well with intense electron

  3. SURVIVAL DEPTH OF ORGANICS IN ICES UNDER LOW-ENERGY ELECTRON RADIATION ({<=}2 keV)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Barnett, Irene Li; Lignell, Antti; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov

    2012-03-01

    Icy surfaces in our solar system are continually modified and sputtered with electrons, ions, and photons from solar wind, cosmic rays, and local magnetospheres in the cases of Jovian and Saturnian satellites. In addition to their prevalence, electrons specifically are expected to be a principal radiolytic agent on these satellites. Among energetic particles (electrons and ions), electrons penetrate by far the deepest into the ice and could cause damage to organic material of possible prebiotic and even biological importance. To determine if organic matter could survive and be detected through remote sensing or in situ explorations on these surfaces, suchmore » as water ice-rich Europa, it is important to obtain accurate data quantifying electron-induced chemistry and damage depths of organics at varying incident electron energies. Experiments reported here address the quantification issue at lower electron energies (100 eV-2 keV) through rigorous laboratory data analysis obtained using a novel methodology. A polycyclic aromatic hydrocarbon molecule, pyrene, embedded in amorphous water ice films of controlled thicknesses served as an organic probe. UV-VIS spectroscopic measurements enabled quantitative assessment of organic matter survival depths in water ice. Eight ices of various thicknesses were studied to determine damage depths more accurately. The electron damage depths were found to be linear, approximately 110 nm keV{sup -1}, in the tested range which is noticeably higher than predictions by Monte Carlo simulations by up to 100%. We conclude that computational simulations underestimate electron damage depths in the energy region {<=}2 keV. If this trend holds at higher electron energies as well, present models utilizing radiation-induced organic chemistry in icy solar system bodies need to be revisited. For interstellar ices of a few micron thicknesses, we conclude that low-energy electrons generated through photoionization processes in the interstellar

  4. Quasi-periodic latitudinal shift of Saturn's main auroral emission

    NASA Astrophysics Data System (ADS)

    Roussos, E.; Palmaerts, B.; Grodent, D. C.; Radioti, K.; Krupp, N.; Yao, Z.

    2017-12-01

    The main component of the ultraviolet auroral emissions at Saturn consists in a ring of emission around each pole of the planet. This main ring of emission has been revealed to oscillate by a few degrees in the prenoon-premidnight direction with a period of 10.8h. This auroral oscillation is thought to be induced by a rotating external magnetospheric current system associated with the planetary period oscillations. Here we report, by means of auroral imaging sequences obtained with the Ultraviolet Imaging Spectrograph (UVIS) on board the Cassini spacecraft, the first direct observation of an additional motion of the main emission superimposed to this oscillation. The whole main emission ring exhibits step-like displacements in latitude mainly towards dayside, decoupled from the 10.8h oscillation. These latitude shifts recur around every hour, which is a typical short periodicity at Saturn previously identified in the aurora intensity, in the charged particle fluxes and in the magnetic field. This unique observation directly demonstrates what has been inferred from past in-situ and remote measurements: the 1-hour periodicities reveal a global and fundamental magnetospheric oscillation mode that acts independently of the local magnetospheric conditions. However, the magnetospheric mechanism responsible for these 1-hour auroral shifts is still unknown. It is possible that Alfvén waves inducing hourly magnetic fluctuations might also modify the place where the field-aligned electrons precipitate in the ionosphere and produce the main emission.

  5. Neutron fluence and energy reconstruction with the IRSN recoil detector μ-TPC at 27 keV, 144 keV and 565 keV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maire, D.; Lebreton, L.; Richer, J.P.

    2015-07-01

    The French Institute for Radioprotection and Nuclear Safety (IRSN), associated to the French Metrology Institute (LNE), is developing a time projection chamber using a Micromegas anode: μ-TPC. This work is carried out in collaboration with the Laboratory of Subatomic Physics and Cosmology (LPSC). The aim is to characterize with a primary procedure the energy distribution of neutron fluence in the energy range 8 keV - 1 MeV. The time projection chambers are gaseous detectors, which are able to measure charged particles energy and to reconstruct their track if a pixelated anode is used. In our case, the gas is usedmore » as a (n, p) converter in order to detect neutrons down to few keV. Coming from elastic collisions with neutrons, recoil protons lose a part of their kinetic energy by ionizing the gas. The ionization electrons are drifted toward a pixelated anode (2D projection), read at 50 MHz by a self-triggered electronic system to obtain the third track dimension. The neutron energy is reconstructed event by event thanks to proton scattering angle and proton energy measurements. The scattering angle is deduced from the 3D track. The proton energy is obtained by charge collection measurements, knowing the ionization quenching factor (i.e. the part of proton kinetic energy lost by ionizing the gas). The fluence is calculated thanks to the detected events number and the simulated detector response. The μ-TPC is a new reliable detector which enables to measure energy distribution of the neutron fluence without deconvolution or neutron calibration contrary to usual gaseous counters. The μ-TPC is still being developed and measurements have been carried out at the AMANDE facility, with neutrons energies going from 8 keV to 565 keV. After the context and the μ-TPC working principle presentation, measurements of the neutron energy and fluence at 27.2 keV, 144 keV and 565 keV are shown and compared to the complete detector simulation. This work shows the first direct

  6. Jupiter's non-auroral Ionosphere and Thermosphere

    NASA Astrophysics Data System (ADS)

    Stallard, T.; Melin, H.; Burrell, A. G.; Hsu, V.; Johnson, R.; Moore, L.; O'Donoghue, J.; Thayer, J. P.

    2017-12-01

    Until recently, our understanding of the non-auroral ionosphere of Jupiter was very limited. However, with the arrival of the Juno spacecraft at Jupiter, we have begun to revise past observations of this region, as well as utilizing modern telescope facilities, in order to reveal a complex array of ionospheric features that show strong coupling with both the local magnetic field and dynamics within the underlying thermosphere. The first feature that was identified was an apparent `Great Dark Spot' in the sub-auroral ionosphere, almost as large as the Great Red Spot. This was observed well away from the northern magnetic pole, mapping to only 2.4 jovian radii. Spectra of the feature showed that it was produced by a 150K cooling in the thermosphere. However, images taken between 1995-2000 showed this feature was consistently observed over two decades at similar magnetic longitudes, but appeared to vary in size, morphology and exact location on a timescale of only days. This suggests that the Great Dark Spot is a large thermospheric vortex driven by auroral heating, similar to transitory features observed at Earth, forming in sub-auroral regions during periods of active aurora. Careful analysis of the Jupiter images then allowed us to measure ionospheric emission down to the equator. This revealed the location of Jupiter's magnetic equator for the first time, appearing as a dark sinusoidal ribbon. This feature appears to be produced as photo-electrons are pushed poleward of the equator when magnetic fields are parallel with the planet's surface, a different process than the dominant plasma fountain that drives Earth's equatorial anomaly. Also revealed were a series of dark spots. Recent Juno magnetometer measurements show that two of these spots appear in regions of high radial magnetic field, suggesting that these regions of the ionosphere are shielded, an inversion of the same process that drives higher ionization in the South Atlantic Anomaly.

  7. Effects of electronic excitation in 150 keV Ni ion irradiation of metallic systems

    NASA Astrophysics Data System (ADS)

    Zarkadoula, Eva; Samolyuk, German; Weber, William J.

    2018-01-01

    We use the two-temperature model in molecular dynamic simulations of 150 keV Ni ion cascades in nickel and nickel-based alloys to investigate the effect of the energy exchange between the atomic and the electronic systems during the primary stages of radiation damage. We find that the electron-phonon interactions result in a smaller amount of defects and affect the cluster formation, resulting in smaller clusters. These results indicate that ignoring the local heating due to the electrons results in the overestimation of the amount of damage and the size of the defect clusters. A comparison of the average defect production to the Norgett-Robinson-Torrens (NRT) prediction over a range of energies is provided.

  8. Plasma Heating and Flow in an Auroral Arc

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Chandler, M. O.; Pollock, C. J.; Reasoner, D. L.; Arnoldy, R. L.; Austin, B.; Kintner, P. M.; Bonnell, J.

    1996-01-01

    We report direct observations of the three-dimensional velocity distribution of selected topside ionospheric ion species in an auroral context between 500 and 550 km altitude. We find heating transverse to the local magnetic field in the core plasma, with significant heating of 0(+), He(+), and H(+), as well as tail heating events that occur independently of the core heating. The 0(+) velocity distribution departs from bi-Maxwellian, at one point exhibiting an apparent ring-like shape. However, these observations are shown to be aliased within the auroral arc by temporal variations that arc not well-resolved by the core plasma instrument. The dc electric field measurements reveal superthermal plasma drifts that are consistent with passage of the payload through a series of vortex structures or a larger scale circularly polarized hydromagnetic wave structure within the auroral arc. The dc electric field also shows that impulsive solitary structures, with a frequency spectrum in the ion cyclotron frequency range, occur in close correlation with the tail heating events. The drift and core heating observations lend support to the idea that core ion heating is driven at low altitudes by rapid convective motions imposed by the magnetosphere. Plasma wave emissions at ion frequencies and parallel heating of the low-energy electron plasma are observed in conjunction with this auroral form; however, the conditions are much more complex than those typically invoked in previous theoretical treatments of superthermal frictional heating. The observed ion heating within the arc clearly exceeds that expected from frictional heating for the light ion species H(+) and He(+), and the core distributions also contain hot transverse tails, indicating an anomalous transverse heat source.

  9. Formation of Electrostatic Potential Drops in the Auroral Zone

    NASA Technical Reports Server (NTRS)

    Schriver, D.; Ashour-Abdalla, M.; Richard, R. L.

    2001-01-01

    In order to examine the self-consistent formation of large-scale quasi-static parallel electric fields in the auroral zone on a micro/meso scale, a particle in cell simulation has been developed. The code resolves electron Debye length scales so that electron micro-processes are included and a variable grid scheme is used such that the overall length scale of the simulation is of the order of an Earth radii along the magnetic field. The simulation is electrostatic and includes the magnetic mirror force, as well as two types of plasmas, a cold dense ionospheric plasma and a warm tenuous magnetospheric plasma. In order to study the formation of parallel electric fields in the auroral zone, different magnetospheric ion and electron inflow boundary conditions are used to drive the system. It has been found that for conditions in the primary (upward) current region an upward directed quasi-static electric field can form across the system due to magnetic mirroring of the magnetospheric ions and electrons at different altitudes. For conditions in the return (downward) current region it is shown that a quasi-static parallel electric field in the opposite sense of that in the primary current region is formed, i.e., the parallel electric field is directed earthward. The conditions for how these different electric fields can be formed are discussed using satellite observations and numerical simulations.

  10. Testing and Comparison of Imaging Detectors for Electrons in the Energy Range 10-20 keV

    NASA Astrophysics Data System (ADS)

    Matheson, J.; Moldovan, G.; Kirkland, A.; Allinson, N.; Abrahams, J. P.

    2017-11-01

    Interest in direct detectors for low-energy electrons has increased markedly in recent years. Detection of electrons in the energy range up to low tens of keV is important in techniques such as photoelectron emission microscopy (PEEM) and electron backscatter diffraction (EBSD) on scanning electron microscopes (SEMs). The PEEM technique is used both in the laboratory and on synchrotron light sources worldwide. The ubiquity of SEMs means that there is a very large market for EBSD detectors for materials studies. Currently, the most widely used detectors in these applications are based on indirect detection of incident electrons. Examples include scintillators or microchannel plates (MCPs), coupled to CCD cameras. Such approaches result in blurring in scintillators/phosphors, distortions in optical systems, and inefficiencies due the limited active area of MCPs. In principle, these difficulties can be overcome using direct detection in a semiconductor device. Growing out of a feasibility study into the use of a direct detector for use on an XPEEM, we have built at Rutherford Appleton Laboratory a system to illuminate detectors with an electron beam of energy up to 20 keV . We describe this system in detail. It has been used to measure the performance of a custom back-thinned monolithic active pixel sensor (MAPS), a detector based on the Medipix2 chip, and a commercial detector based on MCPs. We present a selection of the results from these measurements and compare and contrast different detector types.

  11. The Statistical Studies of 0.5-100 keV Electrons Near The ICME-drivens At 1 AU

    NASA Astrophysics Data System (ADS)

    Yang, L.; Wang, W.; Wang, L.; Li, G.; Wimmer-Schweingruber, R. F.; He, J.; Tu, C. Y.; Bale, S. D.

    2017-12-01

    We present a statistical survey of the 0.5 - 100 keV electrons near the ICME-driven shocks at 1 AU, using the WIND/3DP electron measurements from 1995 to 2014. We select 74 good ICME-driven shocks, and use the "Rankine-Hugoniot" shock fitting technique to obtain the shock normal, θBn, magnetic compression ratio rB, and magnetosonic Mach number Ms. After averaging the electron data in the 10-minute interval immediately after the shock to obtain the sheath electron fluxes, Jsheath, and in the 2-hour quiet-time interval before the shock to obtain the pre-event electron fluxes, Jpre-event, we calculate the flux ratio, α, of Jsheath over Jpre-event. We find that, in the 59 quasi-perpendicular shocks, both Jsheath and Jpre-event are positively correlated with Ms and α is positively correlated with rB. In the 15 quasi-parallel cases, α is positively correlated with Ms, while neither Jsheath nor Jpre-event has any correlation with the shock parameters. Furthermore, we find that both the pre-event and sheath electron fluxes generally fit well to a double power-law spectrum, . At 0.5 - 2 keV, the fitted spectral index β1 ranges from 2.1 to 5.9, and it becomes larger in the sheah than in the pre-event in nearly a half of the 74 cases and remains the same in the other half of the cases. At 2 - 100 keV, the fitted index β2 ranges from 1.9 to 3.4, similar to the spectral indexes of solar wind superhalo electrons at quiet times (Wang et al., 2015). And β2 becomes larger in the sheah than in the pre-event in over half of the cases. In addition, neither β1 nor β2 is consistent with the diffusive shock theoretical predication. These results suggest that the shock drift acceleration may play a more important role in electron acceleration than the diffusive shock acceleration near 1 AU, and the interplanetary shock acceleration can contribute to the production of solar wind superhalo electrons.

  12. By-controlled convection and field-aligned currents near midnight auroral oval for northward interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Taguchi, S.; Sugiura, M.; Iyemori, T.; Winningham, J. D.; Slavin, J. A.

    1994-01-01

    Using the Dynamics Explorer (DE) 2 magnetic and electric field and plasma data, B(sub y)- controlled convection and field-aligned currents in the midnight sector for northward interplanetary magnetic field (IMF) are examined. The results of an analysis of the electric field data show that when IMF is stable and when its magnitude is large, a coherent B(sub y)-controlled convection exists near the midnight auroral oval in the ionosphere having adequate conductivities. When B(sub y) is negative, the convection consists of a westward (eastward) plasma flow at the lower latitudes and an eastward (westward) plasma flow at the higher latitudes in the midnight sector in the northern (southern) ionosphere. When B(sub y) is positive, the flow directions are reversed. The distribution of the field-aligned currents associated with the B(sub y)-controlled convection, in most cases, shows a three-sheet structure. In accordance with the convection the directions of the three sheets are dependent on the sign of B(sub y). The location of disappearance of the precipitating intense electrons having energies of a few keV is close to the convection reversal surface. However, the more detailed relationship between the electron precipitation boundary and the convection reversal surface depends on the case. In some cases the precipitating electrons extend beyond the convection reversal surface, and in others the poleward boundary terminates at a latitude lower than the reversal surface. Previous studies suggest that the poleward boundary of the electrons having energies of a few keV is not necessarily coincident with an open/closed bounary. Thus the open/closed boundary may be at a latitude higher than the poleward boundary of the electron precipitation, or it may be at a latitude lower than the poleward boundary of the electron precipitation. We discuss relationships between the open/closed boundary and the convection reversal surface. When as a possible choice we adopt a view that the

  13. Auroral Proper Motion in the Era of AMISR and EMCCD

    NASA Astrophysics Data System (ADS)

    Semeter, J. L.

    2016-12-01

    The term "aurora" is a catch-all for luminosity produced by the deposition of magnetospheric energy in the outer atmosphere. The use of this single phenomenological term occludes the rich variety of sources and mechanisms responsible for the excitation. Among these are electron thermal conduction (SAR arcs), electrostatic potential fields ("inverted-V" aurora), wave-particle resonance (Alfvenic aurora, pulsating aurora), pitch-angle scattering (diffuse aurora), and direct injection of plasma sheet particles (PBIs, substorms). Much information about auroral energization has been derived from the energy spectrum of primary particles, which may be measured directly with an in situ detector or indirectly via analysis of the atmospheric response (e.g., auroral spectroscopy, tomography, ionization). Somewhat less emphasized has been the information in the B_perp dimension. Specifically, the scale-dependent motions of auroral forms in the rest frame of the ambient plasma provide a means of partitioning both the source region and the source mechanism. These results, in turn, affect ionospheric state parameters that control the M-I coupling process-most notably, the degree of structure imparted to the conductance field. This paper describes recent results enabled by the advent of two technologies: high frame-rate, high-resolution imaging detectors, and electronically steerable incoherent scatter radar (the AMISR systems). In addition to contributing to our understanding of the aurora, these results may be used in predictive models of multi-scale energy transfer within the disturbed geospace system.

  14. Imaging and EISCAT radar measurements of an auroral prebreakup event

    NASA Astrophysics Data System (ADS)

    Safargaleev, V.; Turunen, T.; Lyatsky, W.; Manninen, J.; Kozlovsky, A.

    1996-11-01

    The results of coordinated EISCAT and TV-camera observations of a prebreakup event on 15 November 1993 have been considered. The variations of the luminosity of two parallel auroral arcs, plasma depletion on the poleward edge of one of these arcs as well as electron and ion temperatures in front of a westward travelling surge were studied. It was found that a short-lived brightening of a weak zenith arc before an auroral breakup was accompanied by fading of an equatorial arc and, vice versa. A plasma depletion in the E region was detected by the EISCAT radar on the poleward edge of the zenith arc just before the auroral breakup. The plasma depletion was associated with an enhancement of ion (at the altitudes of 150-200 km) and electron (in E region) temperatures. During its occurrence, the electric field in the E-region was extremely large (sim150 mV/m). A significant increase in ion temperature was also observed 1 min before the arrival of a westward travelling surge (WTS) at the radar zenith. This was interpreted as the existence of an extended area of enhanced electric field ahead of the WTS. Acknowledgements. The work done by P. Henelius and E. Vilenius in programme development is gratefully acknowledged. Topical Editor D. Alcayde thanks I. Pryse and A. Vallance-Jones for their help in evaluating this paper.-> Correspondence to: T. Nygrén->

  15. GaAs Spectrometer for Electron Spectroscopy at Europa

    NASA Astrophysics Data System (ADS)

    Lioliou, G.; Barnett, A. M.

    2016-12-01

    We propose a GaAs based electron spectrometer for a hypothetical future mission orbiting Europa. Previous observations at Europa's South Pole with the Hubble Space Telescope of hydrogen Lyman-α and oxygen OI 130.4 nm emissions were consistent with water vapor plumes [Roth et al., 2014, Science 343, 171]. Future observations and analysis of plumes on Europa could provide information about its subsurface structure and the distribution of liquid water within its icy shells [Rhoden at al. 2015, Icarus 253, 169]. In situ low energy (1keV - 100keV) electron spectroscopy along with UV imaging either in situ or with the Hubble Space Telescope Wide Field Camera 3 or similar would allow verification of the auroral observations being due to electron impact excitation of water vapor plumes. The proposed spectrometer includes a novel GaAs p+-i-n+ photodiode and a custom-made charge-sensitive preamplifier. The use of an early prototype GaAs detector for direct electron spectroscopy has already been demonstrated in ground based applications [Barnett et al., 2012, J. Instrum. 7, P09012]. Based on previous radiation hardness measurements of GaAs, the expected duration of the mission without degradation of the detector performance is estimated to be 4 months. Simulations and laboratory experiments characterising the detection performance of the proposed system are presented.

  16. Comprehensive Ionospheric Polar and Auroral Observations for Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig

    Only the incoherent scatter radar (ISR) is able to simultaneously measure full profiles of elec-tron density, ion temperature, and electron temperatures through the E-and F-layers of the terrestrial ionosphere. Historically ISR's have been operated for periods much less than a month. Hence, their measurements do not constitute a continuous sequence from which quiet, disturbed, and storm periods can reliably be discerned. This is particularly true in the auroral and polar regions. During the International Polar Year (IPY) two ISRs achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the IRI with a fiduciary E-and F-region ionosphere descriptions for solar minimum conditions at auroral and polar cap locations. The ionospheric description being electron den-sity, ion temperature, electron temperature, and even molecular ion composition profiles from as low as 90 km extending several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.4° N, 147.5° W where the NSF's new Poker Flat Incoherent Scatter Radar (PFISR) is located. During solar minimum conditions this location is in the auroral region for most of the day and is at mid-latitudes, equatorward of the cusp, for about 4 to 8 hours per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78° N, 16° E where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap often with a noon sector passage through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be demarked between quiet and disturbed. During the IPY year, 1 March 2007 to 29 February 2008, a total of 50 solar wind corotating interaction regions (CIRs) impacted geospace. Each CIR has a one-to-three day geomagnetic disturbance that is observed in the ISR auroral and polar observations. Hence

  17. Cassini UVIS Auroral Observations in 2016 and 2017

    NASA Astrophysics Data System (ADS)

    Pryor, Wayne R.; Esposito, Larry W.; Jouchoux, Alain; Radioti, Aikaterini; Grodent, Denis; Gustin, Jacques; Gerard, Jean-Claude; Lamy, Laurent; Badman, Sarah; Dyudina, Ulyana A.; Cassini UVIS Team, Cassini VIMS Team, Cassini ISS Team, HST Saturn Auroral Team

    2017-10-01

    In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high-inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) obtained an extensive set of auroral images, some at the highest spatial resolution obtained during Cassini's long orbital mission (2004-2017). In some cases, two or three spacecraft slews at right angles to the long slit of the spectrograph were required to cover the entire auroral region to form auroral images. We will present selected images from this set showing narrow arcs of emission, more diffuse auroral emissions, multiple auroral arcs in a single image, discrete spots of emission, small scale vortices, large-scale spiral forms, and parallel linear features that appear to cross in places like twisted wires. Some shorter features are transverse to the main auroral arcs, like barbs on a wire. UVIS observations were in some cases simultaneous with auroral observations from the Cassini Imaging Science Subsystem (ISS) the Cassini Visual and Infrared Mapping Spectrometer (VIMS), and the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) that will also be presented.

  18. A mathematical model of the structure and evolution of small scale discrete auroral arcs

    NASA Technical Reports Server (NTRS)

    Seyler, C. E.

    1990-01-01

    A three dimensional fluid model which includes the dispersive effect of electron inertia is used to study the nonlinear macroscopic plasma dynamics of small scale discrete auroral arcs within the auroral acceleration zone and ionosphere. The motion of the Alfven wave source relative to the magnetospheric and ionospheric plasma forms an oblique Alfven wave which is reflected from the topside ionosphere by the negative density gradient. The superposition of the incident and reflected wave can be described by a steady state analytical solution of the model equations with the appropriate boundary conditions. This two dimensional discrete auroral arc equilibrium provides a simple explanation of auroral acceleration associated with the parallel electric field. Three dimensional fully nonlinear numerical simulations indicate that the equilibrium arc configuration evolves three dimensionally through collisionless tearing and reconnection of the current layer. The interaction of the perturbed flow and the transverse magnetic field produces complex transverse structure that may be the origin of the folds and curls observed to be associated with small scale discrete arcs.

  19. Effects of electronic excitation in 150 keV Ni ion irradiation of metallic systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zarkadoula, Eva; Samolyuk, German; Weber, William J.

    We use the two-temperature model in molecular dynamic simulations of 150 keV Ni ion cascades in nickel and nickel-based alloys to investigate the effect of the energy exchange between the atomic and the electronic systems during the primary stages of radiation damage. We find that the electron-phonon interactions result in a smaller amount of defects and affect the cluster formation, resulting in smaller clusters. These results indicate that ignoring the local heating due to the electrons results in the overestimation of the amount of damage and the size of the defect clusters. A comparison of the average defect production tomore » the Norgett-Robinson-Torrens (NRT) prediction over a range of energies is provided.« less

  20. Effects of electronic excitation in 150 keV Ni ion irradiation of metallic systems

    DOE PAGES

    Zarkadoula, Eva; Samolyuk, German; Weber, William J.

    2018-01-18

    We use the two-temperature model in molecular dynamic simulations of 150 keV Ni ion cascades in nickel and nickel-based alloys to investigate the effect of the energy exchange between the atomic and the electronic systems during the primary stages of radiation damage. We find that the electron-phonon interactions result in a smaller amount of defects and affect the cluster formation, resulting in smaller clusters. These results indicate that ignoring the local heating due to the electrons results in the overestimation of the amount of damage and the size of the defect clusters. A comparison of the average defect production tomore » the Norgett-Robinson-Torrens (NRT) prediction over a range of energies is provided.« less

  1. Magnetosphere-Ionosphere Coupling in the Auroral Zone

    NASA Technical Reports Server (NTRS)

    Schriver, David

    2004-01-01

    The visual light display at high latitudes referred to as the aurora fascinates casual observers and researchers alike. The natural question is what causes the aurora? We know that energized electrons streaming along the Earth's ambient magnetic field and colliding with atmospheric particles produce aurora. We do not know for certain, however, how these electrons are accelerated to high energies primarily in the field-aligned direction toward the Earth, or what the drivers of this acceleration are. As such, the goal of this Guest Investigator research project was to examine the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region.

  2. A study of a sector spectrophotometer and auroral O+(2P-2D) emissions

    NASA Technical Reports Server (NTRS)

    Swenson, G. R.

    1976-01-01

    The metastable O+(2P-2D) auroral emission was investigated. The neighboring OH contaminants and low intensity levels of the emission itself necessitated the evolution of an instrument capable of separating the emission from the contaminants and having a high sensitivity in the wavelength region of interest. A new type of scanning photometer was developed and its properties are discussed. The theoretical aspects of auroral electron interaction with atomic oxygen and the resultant O+(2P-2D) emissions were examined in conjunction with N2(+)1NEG emissions. Ground based measurements of O+(2P-2D) auroral emission intensities were made using the spatial scanning photometer (sector spectrophotometer). Simultaneous measurements of N2(+)1NEG sub 1,0 emission intensity were made in the same field of view using a tilting photometer. Time histories of the ratio of these two emissions made in the magnetic zenith during auroral breakup periods are given. Theories of I sub 7319/I sub 4278 of previous investigators were presented. A rocket measurement of N2(+)1NEG sub 0,0 and O+(2P-2D) emission in aurora was examined in detail and was found to agree with the ground based measurements. Theoretical examination resulted in the deduction of the electron impact efficiency generating O+(2P) and also suggests a large source of O+(2P) at low altitude. A possible source is charge exchange of N+(1S) with OI(3P).

  3. The Isinglass Auroral Sounding Rocket Campaign: data synthesis incorporating remote sensing, in situ observations, and modelling

    NASA Astrophysics Data System (ADS)

    Lynch, K. A.; Clayton, R.; Roberts, T. M.; Hampton, D. L.; Conde, M.; Zettergren, M. D.; Burleigh, M.; Samara, M.; Michell, R.; Grubbs, G. A., II; Lessard, M.; Hysell, D. L.; Varney, R. H.; Reimer, A.

    2017-12-01

    The NASA auroral sounding rocket mission Isinglass was launched from Poker Flat Alaska in winter 2017. This mission consists of two separate multi-payload sounding rockets, over an array of groundbased observations, including radars and filtered cameras. The science goal is to collect two case studies, in two different auroral events, of the gradient scale sizes of auroral disturbances in the ionosphere. Data from the in situ payloads and the groundbased observations will be synthesized and fed into an ionospheric model, and the results will be studied to learn about which scale sizes of ionospheric structuring have significance for magnetosphere-ionosphere auroral coupling. The in situ instrumentation includes thermal ion sensors (at 5 points on the second flight), thermal electron sensors (at 2 points), DC magnetic fields (2 point), DC electric fields (one point, plus the 4 low-resource thermal ion RPA observations of drift on the second flight), and an auroral precipitation sensor (one point). The groundbased array includes filtered auroral imagers, the PFISR and SuperDarn radars, a coherent scatter radar, and a Fabry-Perot interferometer array. The ionospheric model to be used is a 3d electrostatic model including the effects of ionospheric chemistry. One observational and modelling goal for the mission is to move both observations and models of auroral arc systems into the third (along-arc) dimension. Modern assimilative tools combined with multipoint but low-resource observations allow a new view of the auroral ionosphere, that should allow us to learn more about the auroral zone as a coupled system. Conjugate case studies such as the Isinglass rocket flights allow for a test of the models' intepretation by comparing to in situ data. We aim to develop and improve ionospheric models to the point where they can be used to interpret remote sensing data with confidence without the checkpoint of in situ comparison.

  4. Space Weather Impacts on Spacecraft Design and Operations in Auroral Charging Environments

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Parker, Linda N.

    2012-01-01

    Spacecraft in low altitude, high inclination (including sun-synchronous) orbits are widely used for remote sensing of the Earth s land surface and oceans, monitoring weather and climate, communications, scientific studies of the upper atmosphere and ionosphere, and a variety of other scientific, commercial, and military applications. These systems are episodically exposed to environments characterized by a high flux of energetic (approx.1 to 10 s kilovolt) electrons in regions of very low background plasma density which is similar in some ways to the space weather conditions in geostationary orbit responsible for spacecraft charging to kilovolt levels. While it is well established that charging conditions in geostationary orbit are responsible for many anomalies and even spacecraft failures, to date there have been relatively few such reports due to charging in auroral environments. This presentation first reviews the physics of the space environment and its interactions with spacecraft materials that control auroral charging rates and the anticipated maximum potentials that should be observed on spacecraft surfaces during disturbed space weather conditions. We then describe how the theoretical values compare to the observational history of extreme charging in auroral environments and discuss how space weather impacts both spacecraft design and operations for vehicles on orbital trajectories that traverse auroral charging environments.

  5. Jovian longitudinal asymmetry in Io-related and Europa-related auroral hot spots

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dessler, A.J.; Chamberlain, J.W.

    1979-06-15

    Jupiter's internal magnetic field is markedly non-dipolar. We propose that Io- or Europa-generated auroral emissions (originating at the foot of either Io's or Europa's magnetic flux tube) are largely restricted to longitudes where Jupiter's ionospheric conductivity is enhanced. Trapped, energetic electrons that drift into Jupiter's atmosphere, in regions where the Jovian magnetic field is anomalously weak, produce the increased conductivity. The longitude range of enchanced auroral hot-spot emissions is thus restricted to an active sector that is determined from dekametric radio emission to lie in the northern hemisphere in the Jovian System III (1965) longitude range of 205/sup 0/ +-more » 30/sup 0/. Relatively weaker auroral hot spots should occur in the southern hemisphere along the mgnetic conjugate trace covering the longitude range of 215/sup 0/ +- 55/sup 0/. At other longitudes, the brightness of the hot spot should decrease by at least one order of magnitude. These results, with respect to both brightness and longitude, are in accord with the observations of Jovian auroral hot spots reported by Atreya et al. We show that the northern hemisphere foot of either Io's or Europa's magnetic flux tube was in the preferred longitude range (the active sector) at the time of each observation.« less

  6. Influence of Magnetically Conjugate Fragments of Auroral Emission Images on the Accuracy of Determining E av of Precipitating Electrons

    NASA Astrophysics Data System (ADS)

    Banshchikova, M. A.; Chuvashov, I. N.; Kuzmin, A. K.; Kruchenitskii, G. M.

    2018-05-01

    Results of magnetic conjugation of image fragments of auroral emissions at different altitudes along the magnetic field lines and preliminary results of evaluation of their influence on the accuracy of remote mapping of energy characteristics of precipitating electrons are presented. The results are obtained using the code of tracing being an integral part of the software Vector M intended for calculation of accompanying, geophysical, and astronomical information for the center of mass of a space vehicle (SV) and remote observation of aurora by means of Aurovisor-VIS/MP imager onboard the SV Meteor-MP to be launched.

  7. A Synthesis of Star Calibration Techniques for Ground-Based Narrowband Electron-Multiplying Charge-Coupled Device Imagers Used in Auroral Photometry

    NASA Technical Reports Server (NTRS)

    Grubbs, Guy II; Michell, Robert; Samara, Marilia; Hampton, Don; Jahn, Jorg-Micha

    2016-01-01

    A technique is presented for the periodic and systematic calibration of ground-based optical imagers. It is important to have a common system of units (Rayleighs or photon flux) for cross comparison as well as self-comparison over time. With the advancement in technology, the sensitivity of these imagers has improved so that stars can be used for more precise calibration. Background subtraction, flat fielding, star mapping, and other common techniques are combined in deriving a calibration technique appropriate for a variety of ground-based imager installations. Spectral (4278, 5577, and 8446 A ) ground-based imager data with multiple fields of view (19, 47, and 180 deg) are processed and calibrated using the techniques developed. The calibration techniques applied result in intensity measurements in agreement between different imagers using identical spectral filtering, and the intensity at each wavelength observed is within the expected range of auroral measurements. The application of these star calibration techniques, which convert raw imager counts into units of photon flux, makes it possible to do quantitative photometry. The computed photon fluxes, in units of Rayleighs, can be used for the absolute photometry between instruments or as input parameters for auroral electron transport models.

  8. Simultaneous Measurements of Substorm-Related Electron Energization in the Ionosphere and the Plasma Sheet

    NASA Astrophysics Data System (ADS)

    Sivadas, N.; Semeter, J.; Nishimura, Y.; Kero, A.

    2017-10-01

    On 26 March 2008, simultaneous measurements of a large substorm were made using the Poker Flat Incoherent Scatter Radar, Time History of Events and Macroscale Interactions during Substorm (THEMIS) spacecraft, and all sky cameras. After the onset, electron precipitation reached energies ≳100 keV leading to intense D region ionization. Identifying the source of energetic precipitation has been a challenge because of lack of quantitative and magnetically conjugate measurements of loss cone electrons. In this study, we use the maximum entropy inversion technique to invert altitude profiles of ionization measured by the radar to estimate the loss cone energy spectra of primary electrons. By comparing them with magnetically conjugate measurements from THEMIS-D spacecraft in the nightside plasma sheet, we constrain the source location and acceleration mechanism of precipitating electrons of different energy ranges. Our analysis suggests that the observed electrons ≳100 keV are a result of pitch angle scattering of electrons originating from or tailward of the inner plasma sheet at 9RE, possibly through interaction with electromagnetic ion cyclotron waves. The electrons of energy 10-100 keV are produced by pitch angle scattering due to a potential drop of ≲10 kV in the auroral acceleration region (AAR) as well as wave-particle interactions in and tailward of the AAR. This work demonstrates the utility of magnetically conjugate ground- and space-based measurements in constraining the source of energetic electron precipitation. Unlike in situ spacecraft measurements, ground-based incoherent scatter radars combined with an appropriate inversion technique can be used to provide remote and continuous-time estimates of loss cone electrons in the plasma sheet.

  9. Two-photon coincident emission from thick targets for 70-keV incident electrons

    NASA Astrophysics Data System (ADS)

    Liu, J.; Kahler, D. L.; Quarles, C. A.

    1993-04-01

    Two-photon coincidence yields have been measured in thick targets of C, Al, Ag, and Ta for 70 keV incident electrons and photons radiated at +/-45° to the incident beam. A theoretical model, which is more rigorous, has been developed to simulate the two-photon processes of coherent thick-target double bremsstrahlung (TTDB) and the incoherent emission of two single-bremsstrahlung (SBSB) photons in a thick-target environment. The model is based on an integration of the thin-target cross sections over the target thickness taking into account electron energy loss, electron backscattering, and photon attenuation. It predicts a yield that is much lower than that of the previous model. The prediction of the model fits the present experimental data well by adjusting the relative weight of the two competing processes, and we find that TTDB dominates at low Z and incoherent SBSB dominates at higher Z.

  10. AUREOL-3 observations of new boundaries in the auroral ion precipitation

    NASA Technical Reports Server (NTRS)

    Bosqued, Jean M.; Ashour-Abdalla, Maha; El Alaoui, Mostafa; Zelenyj, Lev M.; Berthlier, Annick

    1993-01-01

    Interesting and well-separated structures in the 1-20 keV ion precipitation pattern have been revealed by an analysis of more than 50 crossings of the nightside (21-03 MLT) auroral zone by the AUREOL-3 satellite. First, velocity-dispersed ion structures (VDIS) are crossed near the poleward edge of the oval, and are the best ionospheric signature of ion beams flowing along the plasma sheet boundary layer. Proceeding equatorward, a large majority of VDIS events are bounded by a new and interesting narrow band of strongly reduced precipitation, or a gap, which delineates VDIS from the diffuse precipitation region connected to the CPS. A statistical analysis shows that the gap has an extent of about 1-2 deg, which is almost independent of magnetic activity; its location, about 70 deg ILAT, shifts significantly equatorward with higher magnetic activity levels. Intense electron arcs are observed near the equatorward edge of the gap. An important result is that the overall sequence of VDIS-gap-CPS can be explained in terms of orbital dynamics in the tail. The gap in precipitation appears as the counterpart of the 'wall' regime in the equatorial plane, in which a cross-tail current carried by energetic ions is strongly enhanced between 8 and 12 R(E). This region has important consequences for the development of substorms.

  11. Observations of Magnetosphere-Ionosphere Coupling Processes in Jupiter's Downward Auroral Current Region

    NASA Astrophysics Data System (ADS)

    Clark, G. B.; Mauk, B.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Bunce, E. J.; Connerney, J. E. P.; Ebert, R. W.; Gershman, D. J.; Gladstone, R.; Haggerty, D. K.; Hospodarsky, G. B.; Kotsiaros, S.; Kollmann, P.; Kurth, W. S.; Levin, S.; McComas, D. J.; Paranicas, C.; Rymer, A. M.; Saur, J.; Szalay, J. R.; Tetrick, S.; Valek, P. W.

    2017-12-01

    Our view and understanding of Jupiter's auroral regions are ever-changing as Juno continues to map out this region with every auroral pass. For example, since last year's Fall AGU and the release of publications regarding the first perijove orbit, the Juno particles and fields teams have found direct evidence of parallel potential drops in addition to the stochastic broad energy distributions associated with the downward current auroral acceleration region. In this region, which appears to exist in an altitude range of 1.5-3 Jovian radii, the potential drops can reach as high as several megavolts. Associated with these potentials are anti-planetward electron angle beams, energetic ion conics and precipitating protons, oxygen and sulfur. Sometimes the potentials within the downward current region are structured such that they look like the inverted-V type distributions typically found in Earth's upward current region. This is true for both the ion and electron energy distributions. Other times, the parallel potentials appear to be intermittent or spatially structured in a way such that they do not look like the canonical diverging electrostatic potential structure. Furthermore, the parallel potentials vary grossly in spatial/temporal scale, peak voltage and associated parallel current density. Here, we present a comprehensive study of these structures in Jupiter's downward current region focusing on energetic particle measurements from Juno-JEDI.

  12. A coincidence study of electron and positron impact ionization of Ar (3p) at 1 keV

    NASA Astrophysics Data System (ADS)

    Campeanu, Radu I.; Walters, James H. R.; Whelan, Colm T.

    2015-10-01

    Distorted-wave calculations of the triple differential cross section (TDCS) are presented for electron and positron impact ionization of Ar(3p) in coplanar asymmetric geometry at an impact energy of 1 keV and are compared with a recent experiment. The experiment indicates that the positron TDCS is generally larger than the equivalent electron TDCS. It is shown that the magnitude of the TDCS is extremely sensitive to the energy of the ejected electron and that only when the cross section is averaged over energy do we get a reasonable agreement with experiment.

  13. The effect of 1 to 5 keV electrons on the reproductive integrity of microorganisms

    NASA Technical Reports Server (NTRS)

    Barengoltz, J. B.; Brady, J.

    1977-01-01

    Microorganisms were exposed to simulated space environment in order to assess the effect of electrons in the energy range 1 to 5 keV on their colony-forming ability. The test system consisted of an electron gun and power supply, a dosimetry subsystem, and a vacuum subsystem. The system was capable of current densities ranging from 0.1 nA/sq cm to 5 micro A/sq cm on a 25 sq on target and an ultimate vacuum of 0.0006 N/sq m (0.000004 torr). The results of the experimental program show a significant reduction in microbial reproductive integrity.

  14. Biological Response of Cancer and Normal Cells on Irradiation from Electrons with Energies up to 200 keV.

    NASA Astrophysics Data System (ADS)

    Prilepskiy, Yuriy

    2007-03-01

    This paper presents continuation data of the series of experiments with the electron gun of the CEBAF machine at Jefferson Lab (Newport News, VA), which is capable of delivering electrons with energies up to 200 keV. This 1.5 GHz beam permits to generate cellular damage within minutes. We have performed irradiation of cancer and normal cells with different electron energies and currents to investigate cell biological responses. The biological response is measured through proteomics analysis before and after irradiation. The living cells are encased in special air containers allowing proper positioning in vacuum where the electrons are present. The containers receive the irradiation from the mono energetic electrons with energy up to 120 keV, resulting in an irradiation from both electrons and a small number of photons from the original beam passing through the thin container window. This window allows approximately half of the beam to come through. The study will permit to address the physical processes involved in the RBE and LET at a level that supersedes current data listed in the literature. We will discuss the experimental setup and the second stage of data collected with the new more developed system. This research is part of a global program to provide detailed information for the understanding of radiation based cancer treatments.

  15. Remote Determination of Auroral Energy Characteristics During Substorm Activity

    NASA Technical Reports Server (NTRS)

    Germany, G. A.; Parks, G. K.; Brittnacher, M. J.; Cumnock, J.; Lummerzheim, D.; Spann, J. F., Jr.

    1997-01-01

    Ultraviolet auroral images from the Ultraviolet Imager onboard the POLAR satellite can be used as quantitative remote diagnostics of the auroral regions, yielding estimates of incident energy characteristics, compositional changes, and other higher order data products. In particular, images of long and short wavelength N2 Lyman-Birge-Hopfield (LBH) emissions can be modeled to obtain functions of energy flux and average energy that are basically insensitive to changes in seasonal and solar activity changes. This technique is used in this study to estimate incident electron energy flux and average energy during substorm activity occurring on May 19, 1996. This event was simultaneously observed by WIND, GEOTAIL, INTERBALL, DMSP and NOAA spacecraft as well as by POLAR. Here incident energy estimates derived from Ultraviolet Imager (UVI) are compared with in situ measurements of the same parameters from an overflight by the DMSP F12 satellite coincident with the UVI image times.

  16. Inferences Concerning the Magnetospheric Source Region for Auroral Breakup

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1992-01-01

    It is argued that the magnetospheric source region for auroral arc breakup and substorm initiation is along boundary plasma sheet (BPS) magnetic field lines. This source region lies beyond a distinct central plasma sheet (CPS) region and sufficiently far from the Earth that energetic ion motion violates the guiding center approximation (i.e., is chaotic). The source region is not constrained to any particular range of distances from the Earth, and substorm initiation may be possible over a wide range of distances from near synchronous orbit to the distant tail. It is also argued that the layer of low-energy electrons and velocity dispersed ion beams observed at low altitudes on Aureol 3 is not a different region from the region of auroral arcs. Both comprise the BPS. The two regions occasionally appear distinct at low altitudes because of the effects of arc field-aligned potential drops on precipitating particles.

  17. Networked high-speed auroral observations combined with radar measurements for multi-scale insights

    NASA Astrophysics Data System (ADS)

    Hirsch, M.; Semeter, J. L.

    2015-12-01

    Networks of ground-based instruments to study terrestrial aurora for the purpose of analyzing particle precipitation characteristics driving the aurora have been established. Additional funding is pouring into future ground-based auroral observation networks consisting of combinations of tossable, portable, and fixed installation ground-based legacy equipment. Our approach to this problem using the High Speed Tomography (HiST) system combines tightly-synchronized filtered auroral optical observations capturing temporal features of order 10 ms with supporting measurements from incoherent scatter radar (ISR). ISR provides a broader spatial context up to order 100 km laterally on one minute time scales, while our camera field of view (FOV) is chosen to be order 10 km at auroral altitudes in order to capture 100 m scale lateral auroral features. The dual-scale observations of ISR and HiST fine-scale optical observations may be coupled through a physical model using linear basis functions to estimate important ionospheric quantities such as electron number density in 3-D (time, perpendicular and parallel to the geomagnetic field).Field measurements and analysis using HiST and PFISR are presented from experiments conducted at the Poker Flat Research Range in central Alaska. Other multiscale configuration candidates include supplementing networks of all-sky cameras such as THEMIS with co-locations of HiST-like instruments to fuse wide FOV measurements with the fine-scale HiST precipitation characteristic estimates. Candidate models for this coupling include GLOW and TRANSCAR. Future extensions of this work may include incorporating line of sight total electron count estimates from ground-based networks of GPS receivers in a sensor fusion problem.

  18. Auroral research at the Tromsø Northern Lights Observatory: the Harang directorship, 1928-1946

    NASA Astrophysics Data System (ADS)

    Egeland, Alv; Burke, William J.

    2016-03-01

    The Northern Lights Observatory in Tromsø began as Professor Lars Vegard's dream for a permanent facility in northern Norway, dedicated to the continuous study of auroral phenomenology and dynamics. Fortunately, not only was Vegard an internationally recognized spectroscopist, he was a great salesman and persuaded the Rockefeller Foundation that such an observatory represented an important long-term investment. A shrewd judge of talent, Vegard recognized the scientific and managerial skills of Leiv Harang, a recent graduate from the University of Oslo, and recommended that he become the observatory's first director. In 1929, subsequent to receiving the Rockefeller Foundation grant, the University of Oslo established a low temperature laboratory to support Vegard's spectroscopic investigations. This paper follows the scientific accomplishments of observatory personnel during the 18 years of Harang's directorship. These include: identifying the chemical sources of auroral emissions, discovering the Vegard-Kaplan bands, quantifying height distributions of different auroral forms, interpreting patterns of magnetic field variations, remotely probing auroral electron distribution profiles in the polar ionosphere, and monitoring the evolving states of the ozone layer. The Rockefeller Foundation judges got it right: the Tromsø Nordlysobservatoriet was, and for decades remained, an outstanding scientific investment.

  19. Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons.

    PubMed

    Zheng, Yi; Sanche, Léon

    2010-10-21

    We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (∼4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons.

  20. Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons

    PubMed Central

    Zheng, Yi; Sanche, Léon

    2011-01-01

    We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (~4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons. PMID:20969428

  1. Auroral excitation of the N2 2P(0,0) and VK(0,9) bands

    NASA Technical Reports Server (NTRS)

    Solomon, Stanley C.

    1989-01-01

    The low-energy secondary electron flux caused by auroral electron precipitation is examined using data from the Atmosphere Explorer C satellite. An energetic electron transport algorithm is used to compute the differential electron flux produced by measured primaries. Emissions of N2 in the 2P(0,0) band at 337 nm and the VK(0,9) band at 335 nm predicted by the model are compared with photometric observation of their combined volume emission rate altitude profile made by the visible airglow experiment. Reasonable correspondence between model and measurement is obtained. Ratios of emissions at 337 nm and 630 nm to the N2(+) 1N(0,0) band at 428 nm are also studied. It is concluded that the 337/428 nm ratio responds to changes in the characteristic energy of primary auroral electrons only insofar as part of the 337 nm brightness is due to N2 VK(0,9) emission. The 630/428 nm ratio, which is strongly dependent on characteristic energy, also varies significantly with changes in atomic oxygen density.

  2. Luminosity variations in several parallel auroral arcs before auroral breakup

    NASA Astrophysics Data System (ADS)

    Safargaleev, V.; Lyatsky, W.; Tagirov, V.

    1997-08-01

    Variation of the luminosity in two parallel auroral arcs before auroral breakup has been studied by using digitised TV-data with high temporal and spatial resolution. The intervals when a new arc appears near already existing one were chosen for analysis. It is shown, for all cases, that the appearance of a new arc is accompanied by fading or disappearance of another arc. We have named these events out-of-phase events, OP. Another type of luminosity variation is characterised by almost simultaneous enhancement of intensity in the both arcs (in-phase event, IP). The characteristic time of IP events is 10-20 s, whereas OP events last about one minute. Sometimes out-of-phase events begin as IP events. The possible mechanisms for OP and IP events are discussed.

  3. Absolute Calibration of Image Plate for electrons at energy between 100 keV and 4 MeV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, H; Back, N L; Eder, D C

    2007-12-10

    The authors measured the absolute response of image plate (Fuji BAS SR2040) for electrons at energies between 100 keV to 4 MeV using an electron spectrometer. The electron source was produced from a short pulse laser irradiated on the solid density targets. This paper presents the calibration results of image plate Photon Stimulated Luminescence PSL per electrons at this energy range. The Monte Carlo radiation transport code MCNPX results are also presented for three representative incident angles onto the image plates and corresponding electron energies depositions at these angles. These provide a complete set of tools that allows extraction ofmore » the absolute calibration to other spectrometer setting at this electron energy range.« less

  4. Research to Operations Transition of an Auroral Specification and Forecast Model

    NASA Astrophysics Data System (ADS)

    Jones, J.; Sanders, S.; Davis, B.; Hedrick, C.; Mitchell, E. J.; Cox, J. M.

    Aurorae are generally caused by collisions of high-energy precipitating electrons and neutral molecules in Earth’s polar atmosphere. The electrons, originating in Earth’s magnetosphere, collide with oxygen and nitrogen molecules driving them to an excited state. As the molecules return to their normal state, a photon is released resulting in the aurora. Aurora can become troublesome for operations of UHF and L-Band radars since these radio frequencies can be scattered by these abundant free electrons and excited molecules. The presence of aurorae under some conditions can lead to radar clutter or false targets. It is important to know the state of the aurora and when radar clutter is likely. For this reason, models of the aurora have been developed and used in an operational center for many decades. Recently, a data-driven auroral precipitation model was integrated into the DoD operational center for space weather. The auroral precipitation model is data-driven in a sense that solar wind observations from the Lagrangian point L1 are used to drive a statistical model of Earth’s aurorae to provide nowcasts and short-duration forecasts of auroral activity. The project began with a laboratory-grade prototype and an algorithm theoretical basis document, then through a tailored Agile development process, deployed operational-grade code to a DoD operational center. The Agile development process promotes adaptive planning, evolutionary development, early delivery, continuous improvement, regular collaboration with the customer, and encourages rapid and flexible response to customer-driven changes. The result was an operational capability that met customer expectations for reliability, security, and scientific accuracy. Details of the model and the process of operational integration are discussed as well as lessons learned to improve performance on future projects.

  5. Performance of different theories for the angular distribution of bremsstrahlung produced by keV electrons incident upon a target

    NASA Astrophysics Data System (ADS)

    Omar, Artur; Andreo, Pedro; Poludniowski, Gavin

    2018-07-01

    Different theories of the intrinsic bremsstrahlung angular distribution (i.e., the shape function) have been evaluated using Monte Carlo calculations for various target materials and incident electron energies between 20 keV and 300 keV. The shape functions considered were the plane-wave first Born approximation cross sections (i) 2BS [high-energy result, screened nucleus], (ii) 2BN [general result, bare nucleus], (iii) KM [2BS modified to emulate 2BN], and (iv) SIM [leading term of 2BN]; (v) expression based on partial-waves expansion, KQP; and (vi) a uniform spherical distribution, UNI [a common approximation in certain analytical models]. The shape function was found to have an important impact on the bremsstrahlung emerging from thin foil targets in which the incident electrons undergo few elastic scatterings before exiting the target material. For thick transmission and reflection targets the type of shape function had less importance, as the intrinsic bremsstrahlung angular distribution was masked by the diffuse directional distribution of multiple scattered electrons. Predictions made using the 2BN and KQP theories were generally in good agreement, suggesting that the effect of screening and the constraints of the Born approximation on the intrinsic angular distribution may be acceptable. The KM and SIM shape functions deviated notably from KQP for low electron energies (< 50 keV), while 2BS and UNI performed poorly over most of the energy range considered; the 2BS shape function was found to be too forward-focused in emission, while UNI was not forward-focused enough. The results obtained emphasize the importance of the intrinsic bremsstrahlung angular distribution for theoretical predictions of x-ray emission, which is relevant in various applied disciplines, including x-ray crystallography, electron-probe microanalysis, security and industrial inspection, medical imaging, as well as low- and medium (orthovoltage) energy radiotherapy.

  6. Triply differential measurements of single ionization of argon by 1-keV positron and electron impact

    NASA Astrophysics Data System (ADS)

    Gavin, J.; de Lucio, O. G.; DuBois, R. D.

    2017-06-01

    By establishing coincidences between target ions and scattered projectiles, and coincidences between target ions, scattered projectiles, and ejected electrons, triply differential cross-section (TDCS) information was generated in terms of projectile energy loss and scattering angles for interactions between 1-keV positrons and electrons and Ar atoms. The conversion of the raw experimental information to the TDCS is discussed. The single-ionization TDCS exhibits two distinguishable regions (lobes) where binary and recoil interactions can be described by two peaks. A comparison of the positron and electron impact data shows that the relative intensity of both binary and recoil interactions decreases exponentially as a function of the momentum transfer and is larger when ionization is induced by positron impact, when compared with electron impact.

  7. A Rocket-Base Study of Auroral Electrodynamics Within the Current Closure Ionosphere

    NASA Technical Reports Server (NTRS)

    Kaeppler, Stephen R.; Kletzing, Craig; Bounds, Scott R.; Sigsbee, Kristine M.; Gjerloev, Jesper W.; Anderson, Brian Jay; Korth, Haje; Lessard, Marc; Labelle, James W.; Dombrowski, Micah P.; hide

    2011-01-01

    The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission, in conjunction with the PFISR Radar, was designed to observe the three-dimensional current system of a stable auroral arc system. ACES utilized two well instrumented payloads flown along very similar magnetic field footprints, at various altitudes with small temporal separation between both payloads. ACES High, the higher altitude payload (apogee 360 km), took in-situ measurements of the plasma parameters above the current closure region to provide the input signature into the lower ionosphere. ACES Low, the low-altitude payload (apogee 130 km), took similar observations within the current closure region, where cross-field currents can flow. We present results comparing observations of the electric fields, magnetic fields, electron flux, and the electron temperature at similar magnetic footpoints between both payloads. We further present data from all-sky imagers and PFISR detailing the evolution of the auroral event as the payloads traversed regions connected by similar magnetic footpoints. Current measurements derived from the magnetometers on both payloads are further compared. We examine data from both PFISR and observations on the high-altitude payload which we interpreted as a signature of electron acceleration by means of Alfv n waves. We further examine all measurements to understand ionospheric conductivity and how energy is being deposited into the ionosphere through Joule heating. Data from ACES is compared against models of Joule heating to make inferences regarding the effect of collisions at various altitudes.

  8. Thermoluminescent response of TLD-100 irradiated with 20 keV electrons and the use of radiochromic dye films for the fluence determination

    NASA Astrophysics Data System (ADS)

    Mercado-Uribe, H.; Brandan, M. E.

    2004-07-01

    We have measured the LiF:Mg,Ti (TLD-100) fluence response and supralinearity function to 20 keV electrons in the fluence interval between 5 × 10 9 and 4 × 10 12 cm -2. TLD-100 shows linear response up to 2 × 10 10 cm -2, followed by supralinearity and saturation after 10 12 cm -2. Peak 5 is slightly supralinear, f( n) max=1.1±0.1, while high temperature peaks reach up to f( n) max≈8. Peak 5 saturates at n≈1×10 11 cm -2, fluence smaller than any of the saturating fluences of the high temperature peaks. We have also measured the glow curve shape of TLD-100 irradiated with 40 keV electrons, beta particles from a 90Sr/ 90Y source and 1.3 and 6.0 MeV electrons from accelerators. Results are interesting and unexpected in that, for a given macroscopic dose, electrons show a smaller relative contribution of high-temperature peaks with respect to peak 5 than heavy ions or X- and γ-rays. The 20 and 40 keV electron irradiations were performed with a scanning electron microscope using radiochromic dye film to measure fluence. Since film calibrations were performed using 60Co γ-rays which expose the totality of the film volume, the use of this method with low energy electrons required to develop a formalism that takes into account the sensitive thickness of the film in relation to the range of the incident particles.

  9. Short-term dynamics of the high-latitude auroral distribution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Murphree, J.S.; Elphinstone, R.D.; Cogger, L.L.

    During two consecutive orbits of the Viking satellite on March 24, 1986, UV observations of the northern hemisphere auroral distribution revealed rapid growth and decay of large-scale polar arcs. Evolution of these features occurred from the nightside auroral distribution (to which they are optically connected) toward the dayside. The connection on the dayside was short-lived ({approx} 2 min) and the arc retreated at similar speeds to its development ({approx} 5 km/s). Time scales for growth (at least to the level of the sensitivity of the instrument) can also be less than 1 min. Examples of arc occurrences during a half-hourmore » time period show that arcs can extend from the nightside to the dayside and disappear and another extended arc can appear at a widely separated position. These types of dynamic polar features appear consistent with the dynamic energization and precipitation of boundary layer electrons at high latitudes.« less

  10. Ion distribution effects of turbulence on a kinetic auroral arc model

    NASA Technical Reports Server (NTRS)

    Cornwall, J. M.; Chiu, Y. T.

    1982-01-01

    An inverted-V auroral arc structure plasma-kinetic model is extended to phenomenologically include the effects of electrostatic turbulence, with k-parallel/k-perpendicular being much less than unity. It is shown that, unless plasma sheet ions are very much more energetic than the electrons, anomalous resistivity is not a large contributor to parallel electrostatic potential drops, since the support of the observed potential drop requires a greater dissipation of energy than can be provided by the plasma sheet. Wave turbulence can, however, be present, with the ion cyclotron turbulence levels suggested by the ion resonance broadening saturation mechanism of Dum and Dupree (1970) being comparable to those observed on auroral field lines. The diffusion coefficient and net growth rate are much smaller than estimates based solely on local plasma properties.

  11. Problems with mapping the auroral oval and magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Antonova, E. E.; Vorobjev, V. G.; Kirpichev, I. P.; Yagodkina, O. I.; Stepanova, M. V.

    2015-10-01

    Accurate mapping of the auroral oval into the equatorial plane is critical for the analysis of aurora and substorm dynamics. Comparison of ion pressure values measured at low altitudes by Defense Meteorological Satellite Program (DMSP) satellites during their crossings of the auroral oval, with plasma pressure values obtained at the equatorial plane from Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite measurements, indicates that the main part of the auroral oval maps into the equatorial plane at distances between 6 and 12 Earth radii. On the nightside, this region is generally considered to be a part of the plasma sheet. However, our studies suggest that this region could form part of the plasma ring surrounding the Earth. We discuss the possibility of using the results found here to explain the ring-like shape of the auroral oval, the location of the injection boundary inside the magnetosphere near the geostationary orbit, presence of quiet auroral arcs in the auroral oval despite the constantly high level of turbulence observed in the plasma sheet, and some features of the onset of substorm expansion.

  12. Problems with mapping the auroral oval and magnetospheric substorms.

    PubMed

    Antonova, E E; Vorobjev, V G; Kirpichev, I P; Yagodkina, O I; Stepanova, M V

    Accurate mapping of the auroral oval into the equatorial plane is critical for the analysis of aurora and substorm dynamics. Comparison of ion pressure values measured at low altitudes by Defense Meteorological Satellite Program (DMSP) satellites during their crossings of the auroral oval, with plasma pressure values obtained at the equatorial plane from Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite measurements, indicates that the main part of the auroral oval maps into the equatorial plane at distances between 6 and 12 Earth radii. On the nightside, this region is generally considered to be a part of the plasma sheet. However, our studies suggest that this region could form part of the plasma ring surrounding the Earth. We discuss the possibility of using the results found here to explain the ring-like shape of the auroral oval, the location of the injection boundary inside the magnetosphere near the geostationary orbit, presence of quiet auroral arcs in the auroral oval despite the constantly high level of turbulence observed in the plasma sheet, and some features of the onset of substorm expansion.

  13. Electron Bremsstrahlung Cross Sections at 25 and 50 keV from Xe and Kr

    NASA Astrophysics Data System (ADS)

    Portillo, Salvador; Quarles, C. A.

    2002-05-01

    Absolute doubly differential bremsstrahlung cross sections for radiation at 90 from 25 and 50 keV electron bombardment of Kr and Xe of will be presented. The electrons were accelerated by a Cockcroft - Walton accelerator into an Al chamber through a .06" Al collimator. Thick target bremsstrahlung background was minimized by having Al nipples and fixtures and by the addition of a carbon lined nipple placed at 180 to the SiLi detector. A comparison of the doubly differential cross sections will be made with current bremsstrahlung theories. The ratio of the Kr and Xe cross sections will also be compared with the theoretical cross section ratios. The ratio provides a more sensitive test of the contribution, if any, of polarization bremsstrahlung.

  14. Global Auroral Remote Sensing Using GGS UVI Images

    NASA Technical Reports Server (NTRS)

    Germany, G. A.; Parks, G. K.; Brittnacher, M. J.; Spann, J. F., Jr.; Cumnock, J.; Lummerzheim, D.

    1997-01-01

    The GGS POLAR satellite, with an apogee distance of 9 Earth radii, provides an excellent platform for extended viewing of the northern auroral zone. Global FUV auroral images from the Ultraviolet Imager onboard the POLAR satellite can be used as quantitative remote diagnostics of the auroral regions, yielding estimates of incident energy characteristics, compositional changes, and other higher order data products. In particular, images of long and short wavelength Earth Far Ultraviolet (FUV) Lyman-Birge-Hopfield (LBH) emissions can be modeled to obtain functions of energy flux and average energy that are basically insensitive to changes in seasonal and solar activity changes. The determination of maps of incident auroral energy characteristics is demonstrated here and compared with in situ measurements.

  15. Polarisation of the auroral red line in the Earth's upper atmosphere: a review (Invited)

    NASA Astrophysics Data System (ADS)

    Lamy, H.; Barthelemy, M.; Lilensten, J.; Bommier, V.; Simon Wedlund, C.

    2013-12-01

    Polarisation of light is a key observable to provide information about asymmetry or anisotropy within a radiative source. Polarimetry of auroral emission lines in the Earth's upper atmosphere has been overlooked for decades. However, the bright red auroral line (6300Å) produced by collisional impact with electrons precipitating along magnetic field lines is a good candidate to search for polarisation. This problem was investigated recently with observations obtained by Lilensten et al (2008), Barthélemy et al (2011) and Lilensten et al (2013) with a photopolarimeter. Analysis of the data indicates that the red auroral emission line is polarised at a level of a few percent. The results are compared to theoretical predictions of Bommier et al (2011) that were obtained for a collimated beam. The comparison suggests the existence of depolarization processes whose origin will be discussed. A new dedicated spectropolarimeter currently under development will also be presented. This instrument will cover the optical spectrum from approximately 400 to 700 nm providing simultaneously the polarisation of the red line and of other interesting auroral emission lines such as N2+ 1NG (4278Å), other N2 bands, etc... The importance of these polarisation measurements in the context of upper atmosphere modelling and geomagnetic activity will be discussed. Lilensten, J. et al, Polarization in aurorae: A new dimension for space environments studies, Geophys. Res. Lett., 26, 269, 2008 Barthélemy M. et al, Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments, Annales Geophysicae, Volume 29, Issue 6, 2011, 1101-1112, 2011. Bommier V. et al, The Theoretical Impact Polarization of the O I 6300 Å Red Line of Earth Auroræ, Annales Geophysicae, Volume 29, Issue 1, 2011, 71-79, 2011 Lilensten, J. et al, The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis, Journal of Space Weather and Space

  16. Total electron scattering cross sections of some important biomolecules at 0.2-6.0 keV energies

    NASA Astrophysics Data System (ADS)

    Gurung, Meera Devi; Ariyasinghe, W. M.

    2017-12-01

    The total electron scattering cross sections (TCS) of five nucleic bases (adenine, cytosine, guanine, thymine and uracil), phosphoric acid, three amino acids (glycine, lysine, and L-histidine), D-glucose, alpha-D-glucose, tetrahydropyran (THP), 3-hydroxytetrahydrofuran and furan have been determined in the energy range 0.2-6.0 keV using a simple model based on the effective atomic total electron scattering cross sections (EATCS). The reliability of the model is confirmed by comparing the determined TCS with the predictions of those by existing theoretical models.

  17. A detector for high frequency modulation in auroral particle fluxes

    NASA Technical Reports Server (NTRS)

    Spiger, R. J.; Oehme, D.; Loewenstein, R. F.; Murphree, J.; Anderson, H. R.; Anderson, R.

    1974-01-01

    A high time resolution electron detector has been developed for use in sounding rocket studies of the aurora. The detector is used to look for particle bunching in the range 50 kHz-10 MHz. The design uses an electron multiplier and an onboard frequency spectrum analyzer. By using the onboard analyzer, the data can be transmitted back to ground on a single 93-kHz voltage-controlled oscillator. The detector covers the 50 kHz-10 MHz range six times per second and detects modulation on the order of a new percent of the total electron flux. Spectra are presented for a flight over an auroral arc.

  18. Polarisation of auroral emission lines in the Earth's upper atmosphere : first results and perspectives

    NASA Astrophysics Data System (ADS)

    Lamy, H.; Barthelemy, M.; Simon Wedlund, C.; Lilensten, J.; Bommier, V.

    2011-12-01

    Polarisation of light is a key observable to provide information about asymmetry or anisotropy within a radiative source. Following the pioneering and controversial work of Duncan in 1959, the polarisation of auroral emission lines in the Earth's upper atmosphere has been overlooked for a long time, even though the red intense auroral line (6300Å) produced by collisional impacts with electrons precipitating along magnetic field lines is a good candidate to search for polarisation. This problem was investigated again by Lilensten et al (2006) and observations were obtained by Lilensten et al (2008) confirming that the red auroral emission line is polarised. More recent measurements obtained by Barthélemy et al (2011) are presented and discussed. The results are compared to predictions of the theoretical work of Bommier et al (2011) and are in good agreement. Following these encouraging results, a new dedicated spectropolarimeter is currently under construction between BIRA-IASB and IPAG to provide simultaneously the polarisation of the red line and of other interesting auroral emission lines such as N2+ 1NG (4278Å), other N2 bands, etc... Perspectives regarding the theoretical polarisation of some of these lines will be presented. The importance of these polarisation measurements in the framework of atmospheric modeling and geomagnetic activity will be discussed.

  19. Controlling Charging and Arcing on a Solar Powered Auroral Orbiting Spacecraft

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Rhee, Michael S.

    2008-01-01

    The Global Precipitation Measurement satellite (GPM) will be launched into a high inclination (65 degree) orbit to monitor rainfall on a global scale. Satellites in high inclination orbits have been shown to charge to high negative potentials, with the possibility of arcing on the solar arrays, when three conditions are met: a drop in plasma density below approximately 10,000 cm(exp -3), an injection of energetic electrons of energy more that 7-10 keV, and passage through darkness. Since all of these conditions are expected to obtain for some of the GPM orbits, charging calculations were done using first the Space Environment and Effects (SEE) Program Interactive Spacecraft Charging Handbook, and secondly the NASA Air-force Spacecraft Charging Analyzer Program (NASCAP-2k). The object of the calculations was to determine if charging was likely for the GPM configuration and materials, and specifically to see if choosing a particular type of thermal white paint would help minimize charging. A detailed NASCAP-2k geometrical model of the GPM spacecraft was built, with such a large number of nodes that it challenged the capability of NASCAP-2k to do the calculations. The results of the calculations were that for worst-case auroral charging conditions, charging to levels on the order of -120 to -230 volts could occur on GPM during night-time, with differential voltages on the solar arrays that might lead to solar array arcing. In sunlit conditions, charging did not exceed -20 V under any conditions. The night-time results were sensitive to the spacecraft surface materials chosen. For non-conducting white paints, the charging was severe, and could continue unabated throughout the passage of GPM through the auroral zone. Somewhat conductive (dissipative) white paints minimized the night-time charging to levels of -120 V or less, and thus were recommended for GPM thermal control. It is shown that the choice of thermal control paints is important to prevent arcing on high

  20. Analysis of Auroral Data from Nasa's 1968 and 1969 Airborne Auroral Expedition

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Results of a methodical compilation, reduction, and correlated analysis of spectrophotometric data obtained by various scientific groups during NASA's 1968 and 1969 Airborne Auroral Expedition are presented.

  1. Transmission of ˜ 10 keV electron beams through thin ceramic foils: Measurements and Monte Carlo simulations of electron energy distribution functions

    NASA Astrophysics Data System (ADS)

    Morozov, A.; Heindl, T.; Skrobol, C.; Wieser, J.; Krücken, R.; Ulrich, A.

    2008-07-01

    Electron beams with particle energy of ~10 keV were sent through 300 nm thick ceramic (Si3N4 + SiO2) foils and the resulting electron energy distribution functions were recorded using a retarding grid technique. The results are compared with Monte Carlo simulations performed with two publicly available packages, Geant4 and Casino v2.42. It is demonstrated that Geant4, unlike Casino, provides electron energy distribution functions very similar to the experimental distributions. Both simulation packages provide a quite precise average energy of transmitted electrons: we demonstrate that the maximum uncertainty of the calculated values of the average energy is 6% for Geant4 and 8% for Casino, taking into account all systematic uncertainties and the discrepancies in the experimental and simulated data.

  2. Observation of hectometric auroral radio emissions in Iceland

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Ono, T.; Iizima, M.; Sato, N.

    2006-12-01

    The Earth's auroral region is an active radio source at frequencies from a few hertz to several megahertz. In the hectometric range, it was found that Terrestrial Hectometric Radiation (THR) is related to auroras by observations of the Ohzora satellite [Oya et al.(1985)]. In resent research, Shinbori et al. [2003] showed that occurrence of THR follows SC by several minutes using the Akebono satellite data. On the ground, auroral roar and MF burst were discovered by Kellogg and Monson [1979, 1984] and Weatherwax et al. [1994] in the northern Canada, respectively. Because there is not enough physical and geophysical characterization of these radio emissions, the physical mechanism of these phenomena in the auroral ionosphere has not been fully understood yet. We set up new observation system at Husafell station in Iceland in September, 2005 and have started to observe auroral radio emissions. Radio signals, which are received by the cross loop antennas, are converted into left- and right- handed polarized components within the frequency range from 1 MHz to 5 MHz. Based on the calibration of system, it was found that the possibility of occurence would be smaller than expected due to the low sensitivity because average power spectrum densities of auroral roar and MF burst are 50-100 nV/m/Hz^1/2. So, the system was planed to be upgraded in this September, which makes it possible to detect auroral roar and MF burst. It is expected that the detail physical process will be elucidated by clarifying the spectrum, polarization, dependence on the geomagnetic activity, and so on. In this presentation, we will show the improved points of the new system and preliminary observation results. There is a basic question whether auroral roar and MF burst observed on the ground are generated by the same process as THR observed by satellites. By comparing the results from the ground-based observation and the Akebono satellite observation of THR, it becomes possible to obtain a new

  3. Comparison of GATE/GEANT4 with EGSnrc and MCNP for electron dose calculations at energies between 15 keV and 20 MeV.

    PubMed

    Maigne, L; Perrot, Y; Schaart, D R; Donnarieix, D; Breton, V

    2011-02-07

    The GATE Monte Carlo simulation platform based on the GEANT4 toolkit has come into widespread use for simulating positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging devices. Here, we explore its use for calculating electron dose distributions in water. Mono-energetic electron dose point kernels and pencil beam kernels in water are calculated for different energies between 15 keV and 20 MeV by means of GATE 6.0, which makes use of the GEANT4 version 9.2 Standard Electromagnetic Physics Package. The results are compared to the well-validated codes EGSnrc and MCNP4C. It is shown that recent improvements made to the GEANT4/GATE software result in significantly better agreement with the other codes. We furthermore illustrate several issues of general interest to GATE and GEANT4 users who wish to perform accurate simulations involving electrons. Provided that the electron step size is sufficiently restricted, GATE 6.0 and EGSnrc dose point kernels are shown to agree to within less than 3% of the maximum dose between 50 keV and 4 MeV, while pencil beam kernels are found to agree to within less than 4% of the maximum dose between 15 keV and 20 MeV.

  4. Effects of 160 keV electron irradiation on the optical properties and microstructure of "Panda" type Polarization-Maintaining optical fibers

    NASA Astrophysics Data System (ADS)

    Hong-Chen, Zhang; Hai, Liu; Hui-Jie, Xue; Wen-Qiang, Qiao; Shi-Yu, He

    2012-11-01

    In this paper, effects of 160 keV electron irradiated "Panda" type Polarization-Maintaining optical fiber at 1310 nm are investigated by us. Attenuation coefficient induced in optical fiber by electron beams at 1310 nm increases with increase in electron fluence. Electron irradiation-induced damage mechanism are studied by means of CASINO simulation program, the X-ray photoelectron spectroscopy (XPS), electron spin resonance spectrometer (EPR) and Fourier transform infrared spectroscopy (FTIR). The results show that Si-OH impurity defect concentration is the main reason of increasing attenuation coefficient at 1310 nm.

  5. Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

    NASA Technical Reports Server (NTRS)

    Knudsen, D. L.; Kabirzadeh, R.; Burchill, J. K.; Pfaff, Robert F.; Wallis, D. D.; Bounds, S. R.; Clemmons, J. H.; Pincon, J.-L.

    2012-01-01

    The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes.

  6. Monte Carlo calculations of energy deposition distributions of electrons below 20 keV in protein.

    PubMed

    Tan, Zhenyu; Liu, Wei

    2014-05-01

    The distributions of energy depositions of electrons in semi-infinite bulk protein and the radial dose distributions of point-isotropic mono-energetic electron sources [i.e., the so-called dose point kernel (DPK)] in protein have been systematically calculated in the energy range below 20 keV, based on Monte Carlo methods. The ranges of electrons have been evaluated by extrapolating two calculated distributions, respectively, and the evaluated ranges of electrons are compared with the electron mean path length in protein which has been calculated by using electron inelastic cross sections described in this work in the continuous-slowing-down approximation. It has been found that for a given energy, the electron mean path length is smaller than the electron range evaluated from DPK, but it is large compared to the electron range obtained from the energy deposition distributions of electrons in semi-infinite bulk protein. The energy dependences of the extrapolated electron ranges based on the two investigated distributions are given, respectively, in a power-law form. In addition, the DPK in protein has also been compared with that in liquid water. An evident difference between the two DPKs is observed. The calculations presented in this work may be useful in studies of radiation effects on proteins.

  7. Interhemispheric Propagation and Interactions of Auroral LSTIDs near the Equator

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Valladares, C.; Carter, B. A.; Doherty, P.

    2016-12-01

    In this work, we used experimental observations based on GPS total electron content (TEC) and ionosonde measurements to study some of the physics behind large-scale traveling ionospheric disturbances (LSTIDs) during the 26 September 2011 geomagnetic storm. In particular, we looked at how these LSTIDs propagate from the auroral zones all the way to the equatorial region and examined how the auroral LSTIDs from opposite hemispheres interact/interfere near the geomagnetic equator. We found that these LSTIDs had an overall propagation speed of ˜700 m/s. Furthermore, the resultant amplitude of the LSTID interference pattern was found to far exceed the sum of individual amplitudes of the incoming LSTIDs. We suspect that this peculiar intensification of auroral LSTIDs around the geomagnetic equator is facilitated by the significantly higher ceiling/canopy of the ionospheric plasma layer there. Normally, acoustic-gravity waves (AGWs) that leak upward (and thus increase in amplitude) would find a negligible level of plasma density at the topside ionosphere. However, the tip of the equatorial fountain at the geomagnetic equator constitutes a significant amount of plasma at a topside-equivalent altitude. The combination of increased AGW amplitudes and a higher plasma density at such altitude would therefore result in higher-amplitude LSTIDs in this particular region, as demonstrated in our observations and analysis.

  8. Comparative Statistical Analysis of Auroral Models

    DTIC Science & Technology

    2012-03-22

    was willing to add this project to her extremely busy schedule. Lastly, I must also express my sincere appreciation for the rest of the faculty and...models have been extensively used for estimating GPS and other communication satellite disturbances ( Newell et al., 2010a). The auroral oval...models predict changes in the auroral oval in response to various geomagnetic conditions. In 2010, Newell et al. conducted a comparative study of

  9. Radiation Damage From Mono-energetic Electrons Up to 200 keV On Biological Systems

    NASA Astrophysics Data System (ADS)

    Prilepskiy, Yuriy

    2006-03-01

    The electron gun of the CEBAF machine at Jefferson lab (Newport News, VA) is capable of delivering electrons with energies up to 200 keV with a resolution of about 10-5. This 1.5 GHz beam permits to generate cellular radiation damage within minutes. We have performed irradiation of cancer cells with different energies and different currents to investigate their biological responses. This study will permit to address the physical processes involved in the RBE and LET at a level that supersedes current data listed in the literature by orders of magnitude. We will discuss the experimental setup and results of the first stage of data collected with this novel system. This research is part of a global program to provide detailed information for the understanding of radiation based cancer treatments.

  10. Pulsating aurora from electron scattering by chorus waves

    NASA Astrophysics Data System (ADS)

    Kasahara, S.; Miyoshi, Y.; Yokota, S.; Mitani, T.; Kasahara, Y.; Matsuda, S.; Kumamoto, A.; Matsuoka, A.; Kazama, Y.; Frey, H. U.; Angelopoulos, V.; Kurita, S.; Keika, K.; Seki, K.; Shinohara, I.

    2018-02-01

    Auroral substorms, dynamic phenomena that occur in the upper atmosphere at night, are caused by global reconfiguration of the magnetosphere, which releases stored solar wind energy. These storms are characterized by auroral brightening from dusk to midnight, followed by violent motions of distinct auroral arcs that suddenly break up, and the subsequent emergence of diffuse, pulsating auroral patches at dawn. Pulsating aurorae, which are quasiperiodic, blinking patches of light tens to hundreds of kilometres across, appear at altitudes of about 100 kilometres in the high-latitude regions of both hemispheres, and multiple patches often cover the entire sky. This auroral pulsation, with periods of several to tens of seconds, is generated by the intermittent precipitation of energetic electrons (several to tens of kiloelectronvolts) arriving from the magnetosphere and colliding with the atoms and molecules of the upper atmosphere. A possible cause of this precipitation is the interaction between magnetospheric electrons and electromagnetic waves called whistler-mode chorus waves. However, no direct observational evidence of this interaction has been obtained so far. Here we report that energetic electrons are scattered by chorus waves, resulting in their precipitation. Our observations were made in March 2017 with a magnetospheric spacecraft equipped with a high-angular-resolution electron sensor and electromagnetic field instruments. The measured quasiperiodic precipitating electron flux was sufficiently intense to generate a pulsating aurora, which was indeed simultaneously observed by a ground auroral imager.

  11. PFISR nightside observations of naturally enhanced ion acoustic lines, and their relation to boundary auroral features

    NASA Astrophysics Data System (ADS)

    Michell, R. G.; Lynch, K. A.; Heinselman, C. J.; Stenbaek-Nielsen, H. C.

    2008-11-01

    We present results from a coordinated camera and radar study of the auroral ionosphere conducted during March of 2006 from Poker Flat, Alaska. The campaign was conducted to coincide with engineering tests of the first quarter installation of the Poker Flat Incoherent Scatter Radar (PFISR). On 31 March 2006, a moderately intense auroral arc, (~10 kR at 557.7 nm), was located in the local magnetic zenith at Poker Flat. During this event the radar observed 7 distinct periods of abnormally large backscattered power from the F-region. These were only observed in the field-aligned radar beam, and radar spectra from these seven times show naturally enhanced ion-acoustic lines (NEIALs), the first observed with PFISR. These times corresponded to (a) when the polar cap boundary of the auroral oval passed through the magnetic zenith, and (b) when small-scale filamentary dark structures were visible in the magnetic zenith. The presence of both (a) and (b) was necessary for their occurrence. Soft electron precipitation occurs near the magnetic zenith during these same times. The electron density in the vicinity where NEIALs have been observed by previous studies is roughly between 5 and 30×1010 m-3. Broad-band extremely low frequency (BBELF) wave activity is observed in situ by satellites and sounding rockets to occur with similar morphology, during active auroral conditions, associated with the poleward edge of the aurora and soft electron precipitation. The observations presented here suggest further investigation of the idea that NEIALs and BBELF wave activity are differently-observed aspects of the same wave phenomenon. If a connection between NEIALs and BBELF can be established with more data, this could provide a link between in situ measurements of downward current regions (DCRs) and dynamic aurora, and ground-based observations of dark auroral structures and NEIALs. Identification of in situ processes, namely wave activity, in ground-based signatures could have many

  12. Sterilization of foods with low-energy electrons (``soft-electrons'')

    NASA Astrophysics Data System (ADS)

    Hayashi, Toru; Takahashi, Yoko; Todoriki, Setsuko

    1998-06-01

    Electrons with an energy of 300 keV or lower were defined as "Soft-electrons", which showed several advantages over conventional irradiation with gamma-rays or high-energy electrons in decontamination of grains and spices. Energies of electrons necessary to reduce microbial loads to levels lower than 10 CFU/g were 60 keV for brown rice, 75 keV for wheat, 100 keV for white pepper, coriander and basil, 130 keV for buckwheat, 160 keV for rough rice, and 210 keV for black pepper. Electrons with such energies did not significantly influence the quality.

  13. Differential Cross Sections for Ionization of Argon by 1 keV Positron and Electron Impact

    NASA Astrophysics Data System (ADS)

    Gavin, J.; DuBois, R. D.; de Lucio, O. G.

    2014-04-01

    Differential information was generated by establishing coincidences and imposing conditions on data recorded for target ions, scattered projectiles, and ejected electrons, as a function of projectile energy loss and scattering angles; in order to describe the interaction between a positron (electron) 1 keV beam and a simple Ar jet. Single ionization triply differential cross section (TDCS) results exhibit two distinct regions (lobes) for which binary (events arising from 2-body interaction) and recoil (events which can only be produced by many-body interactions) interactions are associated. Results indicate that binary events are significantly larger for positron impact, in accordance with theoretical predictions. A similar feature is found for different energy losses and scattering angles. Intensity of the recoil lobe for both projectiles, positron and electron, is observed to depend on the energy loss and scattering angle. Also, it can be noticed that for positron impact the recoil interactions intensity is larger than that observed for electron impact.

  14. Monitoring Auroral Electrojet from Polar Cap Stations

    NASA Astrophysics Data System (ADS)

    Tan, A.; Lyatsky, W.; Lyatskaya, S.

    2004-12-01

    The auroral electrojet AL and AE geomagnetic activity indices are important for monitoring geomagnetic substorms. In the northern hemisphere these indices are derived from measurements at a set of geomagnetic observatories located in the auroral zone. In the southern hemisphere the major portion of the auroral zone is located on the ocean; this does not allow us to derive the auroral electrojet indices in the same way. We showed that monitoring the auroral electrojet is possible from magnetic field measurements at polar cap stations. For this purpose we used hourly values of geomagnetic field variations at four polar cap stations, distributed along polar cap boundary and occupying a longitudinal sector of about 14 hours, and calculated mean values of the total magnetic field disturbance T = (X2 + Y2 + Z2)1/2 where X, Y, and Z are geomagnetic field components measured at these polar cap stations. The set of the obtained values were called the T index. This index has a clear physical mining: it is the summary of geomagnetic disturbance in all three components averaged over the polar cap boundary. We found that correlation coefficients for the dependence of the T index on both AL and AE indices are as high as ~0.9 and higher. The high correlation of the T index with the AL and AE indices takes place for any UT hour when the stations were located at the night side. The T index further shows good correlation with solar wind parameters: the correlation coefficient for the dependence of the T index on the solar wind-geomagnetic activity coupling function is ~0.8 and higher, which is close to the correlation coefficient for AL index. The T index may be especially important in the cases when ground-based measurements in the auroral zone are impossible as in the southern hemisphere.

  15. Relationship between large horizontal electric fields and auroral arc elements

    NASA Astrophysics Data System (ADS)

    Lanchester, B. S.; Kailá, K.; McCrea, I. W.

    1996-03-01

    High time resolution optical measurements in the magnetic zenith are compared with European Incoherent Scatter (EISCAT) field-aligned measurements of electron density at 0.2-s resolution and with horizontal electric field measurements made at 278 km with resolution of 9 s. In one event, 20 min after a spectacular auroral breakup, a system of narrow and active arc elements moved southward into the magnetic zenith, where it remained for several minutes. During a 30-s interval of activity in a narrow arc element very close to the radar beam, the electric field vectors at 3-s resolution were found to be extremely large (up to 400 mVm-1) and to point toward the bright optical features in the arc, which moved along its length. It is proposed that the large electric fields are short-lived and are directly associated with the particle precipitation that causes the bright features in auroral arc elements.

  16. Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1997-01-01

    The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

  17. Scaled experimental investigation of the moderation of auroral cyclotron emissions by background plasma

    NASA Astrophysics Data System (ADS)

    McConville, S. L.; Speirs, D. C.; Gillespie, K. M.; Phelps, A. D. R.; Cross, A. W.; Koepke, M. E.; Whyte, C. G.; Matheson, K.; Robertson, C. W.; Cairns, R. A.; Vorgul, I.; Bingham, R.; Kellett, B. J.; Ronald, K.

    2012-04-01

    Scaled laboratory experiments have been conducted at Strathclyde University [1,2] to further the understanding of the naturally occurring generation of Auroral Kilometric Radiation (AKR) in the Earth's polar magnetosphere. At an altitude of around 3200km there exists a region of partial plasma depletion (the auroral density cavity), through which electrons descend towards the Earth's atmosphere and are subject to magnetic compression. Due to conservation of the magnetic moment these electrons sacrifice parallel velocity for perpendicular velocity resulting in a horseshoe shaped distribution in velocity space which is unstable to the cyclotron maser instability [3,4]. The radiation is emitted at frequencies extending down to the local electron cyclotron frequency with a peak in emission at ~300kHz. The wave propagation is in the X-mode with powers ~109W corresponding to radiation efficiencies of 1% of the precipitated electron kinetic energy [5]. The background plasma frequency within the auroral density cavity is approximately 9kHz corresponding to an electron plasma density ~106m-3. Previous laboratory experiments at Strathclyde have studied cyclotron radiation emission from electron beams which have horseshoe shaped velocity distributions. Radiation measurements showed emissions in X-like modes with powers ~20kW and efficiencies ~1-2%, coinciding with both theoretical and numerical predictions [6-9] and magnetospheric studies. To enhance the experimental reproduction of the magnetospheric environment a Penning trap was designed and incorporated into the existing apparatus [10]. The trap was placed in the wave generation region where the magnetic field would be maintained at ~0.21T. The trap allowed a background plasma to be generated and its characteristics were studied using a plasma probe. The plasma had a significant impact on the radiation generated, introducing increasingly sporadic behaviour with increasing density. The power and efficiency of the radiation

  18. Hard x-ray (>100 keV) imager to measure hot electron preheat for indirectly driven capsule implosions on the NIF.

    PubMed

    Döppner, T; Dewald, E L; Divol, L; Thomas, C A; Burns, S; Celliers, P M; Izumi, N; Kline, J L; LaCaille, G; McNaney, J M; Prasad, R R; Robey, H F; Glenzer, S H; Landen, O L

    2012-10-01

    We have fielded a hard x-ray (>100 keV) imager with high aspect ratio pinholes to measure the spatially resolved bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. These electrons are generated in laser plasma interactions and are a source of preheat to the deuterium-tritium fuel. First measurements show that hot electron preheat does not limit obtaining the fuel areal densities required for ignition and burn.

  19. Impacts of auroral current systems on ionospheric upflow/outflow

    NASA Astrophysics Data System (ADS)

    Burleigh, M.; Zettergren, M. D.; Lynch, K. A.; Lessard, M.; Harrington, M.; Varney, R. H.; Reimer, A.

    2017-12-01

    The downward current region of an auroral current system often contains large perpendicular DC electric fields. These DC electric fields frictionally heat the local ion population resulting in anisotropic increases in ion temperature that cause large pressure gradients which push the ions outward and upward. These ions may undergo further acceleration from transverse heating by broadband ELF waves and at high altitudes the mirror force can propel ions to escape velocities, resulting in outflow to the magnetosphere. Despite these processes being generally well-known, ion outflow remains difficult to predict due to the myriad of processes acting over a large range of altitudes and physical regimes. The resulting temperature anisotropies, which are known to be able to affect upflow, have an unclear degree of impact in highly variable situations like substorm expansions on the nightside or PMAFs/FTEs on the dayside.In this study we use an anisotropic fluid model, GEMINI-TIA, to examine detailed features of temperature anisotropies and resulting ion downflows/upflows/outflows occurring during the ISINGLASS and RENU2 sounding rocket campaigns. GEMINI-TIA is a 2D ionospheric model is based on a truncated 16-moment description and solves the conservation of mass, momentum, parallel energy, and perpendicular energy for species relevant to the E, F, and topside ionospheric regions. This model encapsulates ionospheric upflow and outflow processes through the inclusion of DC electric fields, and empirical descriptions of heating by soft electron precipitation and BBELF waves. The fluid transport equations are accompanied by an electrostatic current continuity equation to self-consistently describe auroral electric fields. Data used to constrain the model can include perpendicular electric fields, characteristic energy, and total energy flux from incoherent scatter radar, any available neutral density and wind measurements, and precipitating electron fluxes. Results from these

  20. DMSP Auroral Charging at Solar Cycle 24 Maximum

    NASA Technical Reports Server (NTRS)

    Chandler, M.; Parker, L. Neergaard; Minow, J. I.

    2013-01-01

    It has been well established that polar orbiting satellites can experience mild to severe auroral charging levels (on the order of a few hundred volts to few kilovolts negative frame potentials) during solar minimum conditions. These same studies have shown a strong reduction in charging during the rising and declining phases of the past few solar cycles with a nearly complete suppression of auroral charging at solar maximum. Recently, we have observed examples of high level charging during the recent approach to Solar Cycle 24 solar maximum conditions not unlike those reported by Frooninckx and Sojka. These observations demonstrate that spacecraft operations during solar maximum cannot be considered safe from auroral charging when solar activity is low. We present a survey of auroral charging events experienced by the Defense Meteorological Satellite Program (DMSP) F16 satellite during Solar Cycle 24 maximum conditions. We summarize the auroral energetic particle environment and the conditions necessary for charging to occur in this environment, we describe how the lower than normal solar activity levels for Solar Cycle 24 maximum conditions are conducive to charging in polar orbits, and we show examples of the more extreme charging events, sometimes exceeding 1 kV, during this time period.

  1. DMSP Auroral Charging at Solar Cycle 24 Maximum

    NASA Technical Reports Server (NTRS)

    Chandler, Michael; Parker, Linda Neergaard; Minow, Joseph I.

    2013-01-01

    It has been well established that polar orbiting satellites can experience mild to severe auroral charging levels (on the order of a few hundred volts to few kilovolts negative frame potentials) during solar minimum conditions (Frooninckx and Sojka, 1992; Anderson and Koons, 1996; Anderson, 2012). These same studies have shown a strong reduction in charging during the rising and declining phases of the past few solar cycles with a nearly complete suppression of auroral charging at solar maximum. Recently, we have observed examples of high level charging during the recent approach to Solar Cycle 24 solar maximum conditions not unlike those reported by Frooninckx and Sojka (1992). These observations demonstrate that spacecraft operations during solar maximum cannot be considered safe from auroral charging when solar activity is low. We present a survey of auroral charging events experienced by the Defense Meteorological Satellite Program (DMSP) F16 satellite during Solar Cycle 24 maximum conditions. We summarize the auroral energetic particle environment and the conditions necessary for charging to occur in this environment, we describe how the lower than normal solar activity levels for Solar Cycle 24 maximum conditions are conducive to charging in polar orbits, and we show examples of the more extreme charging events, sometimes exceeding 1 kV, during this time period.

  2. Solar wind control of stratospheric temperatures in Jupiter's auroral regions?

    NASA Astrophysics Data System (ADS)

    Sinclair, James Andrew; Orton, Glenn; Kasaba, Yasumasa; Sato, Takao M.; Tao, Chihiro; Waite, J. Hunter; Cravens, Thomas; Houston, Stephen; Fletcher, Leigh; Irwin, Patrick; Greathouse, Thomas K.

    2017-10-01

    Auroral emissions are the process through which the interaction of a planet’s atmosphere and its external magnetosphere can be studied. Jupiter exhibits auroral emission at a multitude of wavelengths including the X-ray, ultraviolet and near-infrared. Enhanced emission of CH4 and other stratospheric hydrocarbons is also observed coincident with Jupiter’s shorter-wavelength auroral emission (e.g. Caldwell et al., 1980, Icarus 44, 667-675, Kostiuk et al., 1993, JGR 98, 18823). This indicates that auroral processes modify the thermal structure and composition of the auroral stratosphere. The exact mechanism responsible for this auroral-related heating of the stratosphere has however remained elusive (Sinclair et al., 2017a, Icarus 292, 182-207, Sinclair et al., 2017b, GRL, 44, 5345-5354). We will present an analysis of 7.8-μm images of Jupiter measured by COMICS (Cooled Mid-Infrared Camera and Spectrograph, Kataza et al., 2000, Proc. SPIE(4008), 1144-1152) on the Subaru telescope. These images were acquired on January 11th, 12th, 13th, 14th, February 4, 5th and May 17th, 18th, 19th and 20th in 2017, allowing the daily variability of Jupiter’s auroral-related stratospheric heating to be tracked. Preliminary results suggest lower stratospheric temperatures are directly forced by the solar wind dynamical pressure. The southern auroral hotspot exhibited a significant increase in brightness temperature over a 24-hour period. Over the same time period, a solar wind propagation model (Tao et al. 2005, JGR 110, A11208) predicts a strong increase in the solar wind dynamical pressure at Jupiter.

  3. Ionization rate from the electron precipitation during August 2011 storm

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Huang, C. Y.; Su, Y.

    2013-12-01

    We apply a parameterization by Fang et al. [2010] (Fang2010) to the complex energy spectra measured by DMSP F16 satellites to calculate the ionization rate from electron precipitation during a moderate storm on August 6th, 2011. The DMSP electron flux measurements show that there is clear enhancement of electron fluxes in the polar cap. The mean energy in the polar cap is mostly above 100 eV, while the mean energy of auroral zone is above 1 keV. F16 also captures a strong Poynting flux enhancement in the polar cap. The electron impact ionization rates using thermospheric densities and temperatures from NRLMSISE-00, TIE-GCM and GITM show clear enhancement at F-region altitudes in the polar cap region due to the low-energy electrons precipitated. Using the default empirical formulations of electron impact ionization in GCMs, TIE-GCM and GITM do not capture the F-region ionization shown in the results of Fang2010 parameterization. Fang, X, C. E. Randall, D. Lummerzheim, W. Wang, G. Lu, S. C. Solomon, and R. A. Frahm (2010), Geophys. Res. Lett., 37, L22106, doi:10.1029/2010GL045406.

  4. New frontiers in H-Beta auroral photometry

    NASA Astrophysics Data System (ADS)

    Unick, C.; Donovan, E.; Connors, M. G.; Spanswick, E.; Jackel, B. J.; Greffen, M. J.; Wilson, C.; Little, J.; Chaddock, D.; Schofield, I.; MacRae, A.; Chen, S.; Crowther, A.; James, S.; Read, A.; Willis, T.

    2013-12-01

    The proton aurora provides valuable information about magnetotail structure and dynamics. For example, the location of the equatorward boundary of the proton aurora is a robust indicator of magnetotail stretching. Also, proton auroral luminosities combined with in situ ion measurements provide important information about magnetic mapping between the inner CPS and the auroral ionosphere. In this paper, we present a new and innovative proton-auroral (H-Beta) meridian-scanning photometer (MSP) capable of higher spatial and temporal resolution than has been achieved in the past. This H-Beta MSP is the first of a new dual-wavelength (signal/background) MSP design with a single scanning mirror and no other moving parts. The novel filtering architecture allows for a near 100% duty cycle with a 30-second meridian scan and configurable operating modes. The new design is significantly more sensitive than the legacy CANOPUS MSPs. The increased SNR can be employed in a variety of ways, such as to achieve significantly higher time resolution. Here, we present the new instrument design, test data from a commissioning campaign in Athabasca, and some thoughts on how the enhance proton auroral capability can increase the science value of these measurements.

  5. The stimulation of auroral kilometric radiation by type III solar radio bursts

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1981-01-01

    It has been found that the onset of auroral kilometric radiation (AKR) frequently coincides with the arrival of type III solar radio bursts. Although the AKR onsets are usually abrupt and appear to be spontaneous, they sometimes develop from a discrete frequency near the leading edge of a type III burst or sometimes occur at progressively lower frequencies following that edge. From this, and the absence of the related solar electrons in specific cases, it was concluded that the incoming type III waves were sometimes responsible for stimulating auroral kilometric radiation. It was estimated that intense, isolated type III bursts were capable of stimulating AKR roughly one third of the time, and that at least ten percent of the observed AKR onsets could be attributed to these and weaker bursts, including some barely detectable by the ISEE plasma wave receivers.

  6. Origin of Si(LMM) Auger Electron Emission from Silicon and Si-Alloys by keV Ar+ Ion Bombardment

    NASA Astrophysics Data System (ADS)

    Iwami, Motohiro; Kim, Su Chol; Kataoka, Yoshihide; Imura, Takeshi; Hiraki, Akio; Fujimoto, Fuminori

    1980-09-01

    Si(LMM) Auger electrons emitted from specimens of pure silicon and several Si-alloys (Ni-Si, Pd-Si and Cu-Si) under keV Ar+ ion bombardment, were examined. In the Auger spectra from all specimens studied there were four peaks at energies of 92, 86, 76 and 66 eV. The Auger signal intensity varied considerably with both the incident angle and the energy of the primary ion beam. It is proposed that the Auger electrons are emitted from silicon atoms (or ions) just beneath the specimen surface but free from the bulk network.

  7. The Harang discontinuity in auroral belt ionospheric currents.

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1972-01-01

    Discussion of the nature of a discontinuity in the ionospheric current of the auroral belt whose existence was suggested by Harang in 1946. Convection characteristics, time variability, and current continuity in the auroral belt are considered in a context of observations and arguments supporting the reality of Harang's discontinuity.

  8. Theoretical and experimental studies relevant to interpretation of auroral emissions

    NASA Technical Reports Server (NTRS)

    Keffer, Charles E.

    1994-01-01

    This report describes the accomplishments of a program designed to develop the tools necessary to interpret auroral emissions measured from a space-based platform. The research was divided into two major areas. The first area was a laboratory study designed to improve our understanding of the space vehicle external environment and how it will affect the space-based measurement of auroral emissions. Facilities have been setup and measurements taken to simulate the gas phase environment around a space vehicle; the radiation environment encountered by an orbiting vehicle that passes through the Earth's radiation belts; and the thermal environment of a vehicle in Earth orbit. The second major area of study was a modeling program to develop the capability of using auroral images at various wavelengths to infer the total energy influx and characteristic energy of the incident auroral particles. An ab initio auroral calculation has been added to the extant ionospheric/thermospheric global modeling capabilities within our group. Once the addition of the code was complete, the combined model was used to compare the relative intensities and behavior of various emission sources (dayglow, aurora, etc.). Attached papers included are: 'Laboratory Facility for Simulation of Vehicle-Environment Interactions'; 'Workshop on the Induced Environment of Space Station Freedom'; 'Radiation Damage Effects in Far Ultraviolet Filters and Substrates'; 'Radiation Damage Effects in Far Ultraviolet Filters, Thin Films, and Substrates'; 'Use of FUV Auroral Emissions as Diagnostic Indicators'; and 'Determination of Ionospheric Conductivities from FUV Auroral Emissions'.

  9. UCB current detector experiment on Swedish auroral payloads. [ionospheric current and plasma flow measurements

    NASA Technical Reports Server (NTRS)

    Mozer, F.

    1974-01-01

    A split Langmuir probe has been developed to make in situ measurements of ionospheric current density and plasma bulk flow. The probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2 pi solid angle, and that are simultaneously swept from negative to positive with respect to the plasma. By measuring the current to each plate and the difference current between plates, information is obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully flown twice on sounding rockets into auroral events. Measurement data indicate that the total auroral current configuration is composed of several alternating east and west electrojets associated with several alternating up and down Birkeland currents.

  10. Rocket study of auroral processes

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.

    1981-01-01

    Abstracts are presented of previously published reports analyzing data from three Echo 3 rocket flights. Particle experiments designed for the Terrier-Malmute flight, the Echo 5 flight, and the Norwegian Corbier Ferdinand 50 flight are described and their flight performance evaluated. Theoretical studies on auroral particle precipitation are reviewed according to observations made in three regions of space: (1) the region accessible to rockets and low altitude satellites (few hundred to a few thousand kilometers); (2) the region extending from 4000 to 8000 km (S3-3 satellite range); and (3) near the equatorial plane (geosynchronous satellite measurements). Questions raised about auroral arc formation are considered.

  11. Space Weather Monitoring for ISS Space Environments Engineering and Crew Auroral Observations

    NASA Technical Reports Server (NTRS)

    Minow, Joseph; Pettit, Donald R.; Hartman, William A.

    2012-01-01

    Today s presentation describes how real time space weather data is used by the International Space Station (ISS) space environments team to obtain data on auroral charging of the ISS vehicle and support ISS crew efforts to obtain auroral images from orbit. Topics covered include: Floating Potential Measurement Unit (FPMU), . Auroral charging of ISS, . Real ]time space weather monitoring resources, . Examples of ISS auroral charging captured from space weather events, . ISS crew observations of aurora.

  12. Morphology of Southern Hemisphere Riometer Auroral Absorption

    DTIC Science & Technology

    2006-06-01

    Departamento de Geofísica Universidad de Concepción, Concepción CHILE foppiano@udec.cl ABSTRACT A morphology of riometer auroral absorption is...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Departamento de Geofísica Universidad de ...range of frequencies used an inverse -square frequency dependence approximately holds. Morphology of Southern Hemisphere Riometer Auroral Absorption

  13. Coordinated analysis of various auroral measurements made during NASA's 1968 and 1969 airborne auroral expeditions

    NASA Technical Reports Server (NTRS)

    Sivjee, G. G.

    1976-01-01

    Auroral optical measurements made aboard NASA's CV 990 were analyzed. The measurements analyzed form a small part of extensive spectroscopic, photometric and photographic data gathered during the 1968 and 1969 Airborne Auroral Expeditions. Simultaneous particle measurements from ESRO IA satellite were used in the analysis. Information about magnetospheric boundaries, interaction between magnetosheath particles and the terrestrial ionosphere, the polar bulge in helium abundance and excitation mechanisms of the triplet state of atmospheric N2 in auroras was obtained. Further analysis of the data is required to elucidate the relation between 3466 and 5200 A emissions of NI and the excitation of 3726-3729 A emissions from atomic oxygen ions in auroras.

  14. Van Allen Probes observations of intense parallel Poynting flux associated with magnetic dipolarization, conjugate discrete auroral arcs, and energetic particle injection

    NASA Astrophysics Data System (ADS)

    Wygant, J. R.; Thaller, S. A.; Breneman, A. W.; Tian, S.; Cattell, C. A.; Chaston, C. C.; Mozer, F.; Bonnell, J. W.; Kistler, L. M.; Mouikis, C.; Hudson, M. K.; Claudepierre, S. G.; Fennell, J. F.; Reeves, G. D.; Baker, D. N.; Donovan, E.; Spanswick, E.; Kletzing, C.

    2015-12-01

    We present measurements from the Van Allen Probes, in the near Earth tail, at the outer boundary of the plasma sheet, of a magnetic dipolarization/injection event characterized by unusually strong earthward poynting flux flowing along magnetic field lines with amplitudes of 200 mW/m2 lasting ~ 1 minute. The Poynting flux was conjugate to a 30 km wide discrete auroral arc observed by the THEMIS auroral array. The observations were obtained at 5.8 Re in the pre-midnight sector during the main phase of a geomagnetic storm on 5/01/2013. This brief interval transferred more electromagnetic energy (at the spacecraft position) than that transferred during entire remainder of the main phase of the storm. The parallel Poynting flux coincided with a local section of the "cross tail current sheet" which generated the dipolarization signature. The latitudinal width of the arc, mapped along magnetic field lines, provides an estimate of the spatial scale of the Poynting flux, the electric fields, and the current sheets (parallel and perpendicular). It is estimated that the latitudinal width of the Poynting flux "sheet" was ~600 km or ~1-2 H+ inertial lengths. An estimate of the ∫E·dl across the current sheet along the direction normal to the plasma sheet is ~20-40 kilovolts. The "normal" to the plasma sheet component of the electric field (~70 mV/m) strongly dominated the azimuthal component(which is reponsible for drift energetization). The dipolarization event resulted in the local dispersion-less injection of electrons between 50 keV and ~2 MeV at the Van Allen Probe position. The injection event involved brief (factor of two) local spike in ~2 MeV electron fluxes. Measurements from the Los Alamos geosynchronous spacecraft, displaced eastward from the Van Allen probes, provided evidence for dispersive energy-time electron signatures consistent with injection and energization at the RBSP position. The Poynting flux also coincided with the energy peak in the up

  15. The angular distribution of solar wind ˜20-200 keV superhalo electrons at quiet times

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Wang, Linghua; Li, Gang; He, Jiansen; Salem, Chadi S.; Tu, Chuanyi; Wimmer-Schweingruber, Robert F.; Bale, Stuart D.

    2016-03-01

    We present a comprehensive study of the angular distribution of ˜20-200 keV superhalo electrons measured at 1 AU by the WIND 3DP instrument during quiet times from 1995 January through 2005 December. According to the interplanetary magnetic field, we re-bin the observed electron pitch angle distributions to obtain the differential flux, Jout (Jin), of electrons traveling outward from (inward toward) the Sun, and define the anisotropy of superhalo electrons as A =2/(Jo u t-Ji n) Jo u t+Ji n at a given energy. We found that for out in ˜96% of the selected quiet-time samples, superhalo electrons have isotropic angular distributions, while for ˜3% (˜1%) of quiet-time samples, superhalo electrons are outward-anisotropic (inward-anisotropic). All three groups of angular distributions show no correlation with the local solar wind plasma, interplanetary magnetic field and turbulence. Furthermore, the superhalo electron spectral index shows no correlation with the spectral index of local solar wind turbulence. These quiet-time superhalo electrons may be accelerated by nonthermal processes related to the solar wind source and strongly scattered/ reflected in the interplanetary medium, or could be formed due to the electron acceleration through the interplanetary medium.

  16. Infrasonic waves generated by supersonic auroral arcs

    NASA Astrophysics Data System (ADS)

    Pasko, Victor P.

    2012-10-01

    A finite-difference time-domain (FDTD) model of infrasound propagation in a realistic atmosphere is used to provide quantitative interpretation of infrasonic waves produced by auroral arcs moving with supersonic speed. The Lorentz force and Joule heating are discussed in the existing literature as primary sources producing infrasound waves in the frequency range 0.1-0.01 Hz associated with the auroral electrojet. The results are consistent with original ideas of Swift (1973) and demonstrate that the synchronization of the speed of auroral arc and phase speed of the acoustic wave in the electrojet volume is an important condition for generation of magnitudes and frequency contents of infrasonic waves observable on the ground. The reported modeling also allows accurate quantitative reproduction of previously observed complex infrasonic waveforms including direct shock and reflected shockwaves, which are refracted back to the earth by the thermosphere.

  17. Investigating the auroral electrojets using Swarm

    NASA Astrophysics Data System (ADS)

    Smith, Ashley; Macmillan, Susan; Beggan, Ciaran; Whaler, Kathy

    2016-04-01

    The auroral electrojets are large horizontal currents that flow within the ionosphere in ovals around the polar regions. They are an important aspect of space weather and their position and intensity vary with solar wind conditions and geomagnetic activity. The electrojet positions are also governed by the Earth's main magnetic field. During more active periods, the auroral electrojets typically move equatorward and become more intense. This causes a range of effects on Earth and in space, including geomagnetically induced currents in power transmission networks, disturbance to radio communications and increased drag on satellites due to expansion of the atmosphere. They are also indicative of where the aurora are visible. Monitoring of the auroral electrojets in the pre-satellite era was limited to the network of ground-based magnetic observatories, from which the traditional AE activity indices are produced. These suffer in particular from the stations' poor distribution in position and so this motivates the use of satellite-based measurements. With polar low-Earth orbit satellites carrying magnetometers, all latitudes can be sampled with excellent resolution. This poster presents an investigation using Swarm's magnetometer data to detect the electrojets as the spacecraft move above them. We compare and contrast two approaches, one which uses vector data and the other which uses scalar data (Hamilton and Macmillan 2013, Vennerstrom and Moretto, 2013). Using ideas from both approaches we determine the oval positions and intensities from Swarm and earlier satellites. The variation in latitude and intensity with solar wind conditions, geomagnetic activity and secular variation of the main field is investigated. We aim to elucidate the relative importance of these factors. Hamilton, B. and Macmillan, S., 2013. Investigation of decadal scale changes in the auroral oval positions using Magsat and CHAMP data. Poster at IAGA 12th Scientific Assembly, 2013. http

  18. Latitudinal Variations of Auroral-Zone Ionization Distribution.

    DTIC Science & Technology

    1983-02-01

    CONTRACT OR GRANT NUMBER(s) Robert M. Robinson F49620-80-C-0014 Roland T. Tsunoda 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT , PROJECT...scanned. A. Auroral Zone Ionospheric Conductivity A key element in modelling the magnetosphere-ionosphere circuit is the auroral zone ionospheric...while the maximum conductivity for the evening eastward electro- jet was less than 20 mho in our data set . In other words, both the south- ward field and

  19. ESA's Cluster solved an auroral puzzle

    NASA Astrophysics Data System (ADS)

    2003-05-01

    These aurorae - seen as bright spots in Earth’s atmosphere and called ‘dayside proton auroral spots’ - occur when fractures appear in the Earth’s magnetic field, allowing particles given out from the Sun to squirt through and collide with the molecules in our atmosphere. This is the first time that a precise and direct connection between the two events has been made. The Earth’s magnetic field acts like a shield, protecting Earth from the constant stream of tiny particles ejected by the Sun and known as the ‘solar wind’. The solar wind itself is made of hydrogen atoms, broken into their constituent pieces: protons and electrons. When electrons find routes into our atmosphere, they collide with and excite the atoms in the air. When these excited atoms release their energy, it is given out as light, creating the glowing ‘curtains’ we see as the aurora borealis (or the aurora australis in the southern hemisphere). Dayside proton auroral spots are caused by protons ‘stealing’ electrons from the atoms in our atmosphere. On 18 March last year, a jet of energetic solar protons collided with the Earth’s atmosphere and created a bright ‘spot’ seen by NASA’s IMAGE spacecraft, just as Cluster passed overhead and straight through the region where the proton jet was emanating. An extensive analysis of the Cluster results has now shown that the region was experiencing a turbulent event known as ‘magnetic reconnection’. Such a phenomenon takes place when the Earth’s usually impenetrable magnetic field fractures and has to find a new stable configuration. Until the field mends itself, solar protons leak through the gap and jet into Earth’s atmosphere creating the dayside proton aurora. Philippe Escoubet, ESA’s Cluster Project Scientist, comments, “Thanks to Cluster’s observations scientists can directly and firmly link for the first time a dayside proton auroral spot and a magnetic reconnection event.” Tai Phan, leading the

  20. Analytic model of aurorally coupled magnetospheric and ionospheric electrostatic potentials

    NASA Technical Reports Server (NTRS)

    Cornwall, J. M.

    1994-01-01

    This paper describes modest but significant improvements on earlier studies of electrostatic potential structure in the auroral region using the adiabatic auroral arc model. This model has crucial nonlinearities (connected, for example. with aurorally produced ionization) which have hampered analysis; earlier work has either been linear, which I will show is a poor approximation or, if nonlinear, either numerical or too specialized to study parametric dependencies. With certain simplifying assumptions I find new analytic nonlinear solutions fully exhibiting the parametric dependence of potentials on magnetospheric (e.g.. cross-tail potential) and ionospheric (e.g., recombination rate) parameters. No purely phenomenological parameters are introduced. The results are in reasonable agreement with observed average auroral potential drops, inverted-V scale sizes, and dissipation rates. The dissipation rate is quite comparable to tail energization and transport rates and should have a major effect on tail and magnetospheric dynamics. This paper gives various relations between the cross-tail potential and auroral parameters (e.g., total parallel currents and potential drops) which can be studied with existing data sets.

  1. Ionospheric Convection in the Postnoon Auroral Oval: SuperDARN and Polar UVI Observations

    NASA Technical Reports Server (NTRS)

    Kozlovsky, A.; Koustov, A.; Lyatsky, W.; Kangas, J.; Parks, G.; Chua, D.

    2002-01-01

    Super Dual Auroral Radar Network (SuperDARN) observations, ultraviolet imaging from the Polar satellite (UVI), and particle precipitation data from DMSP satellites have been used to investigate the electrodynamics of the postnoon auroral oval in the Northern hemisphere. We show that: (1) For negative IMF By, the convection reversal (CR) was co-located with the maximum of auroral luminosity, but during positive IMF By the convection reversal was poleward of the auroral oval up to several degrees in latitude; (2) Postnoon auroral oval was associated with a large-scale upward field-aligned current (FAC) of the order of 6x10(exp -7). A m(exp -2) in magnitude (the FAC was inferred from the SuperDARN and UVI data). For negative IMF By, maximum of the auroral intensity coincides in latitude with the maximum of the upward field-aligned current. However, for positive IMF By. the maximum of the upward FAC was shifted to the poleward edge of the auroral oval; (3) In response to the IMF By turning from positive to negative, the maximum of the auroral luminosity did not change its position noticeably, but the position of the convection reversal changed considerably from 80-81 degs to about 76 degs MLAT, and the maximum of FAC moved from 77-78 degs to about 76 degs MLAT. Thus, after IMF By turns negative, both the FAC maximum and CR tend to coincide with the auroral maximum; (4) The IMF Bz positive deflection was followed by a decrease in both field-aligned current intensity and auroral luminosity. However, the decrease in the auroral luminosity lags behind the FAC decrease by about 12 min. Firstly, these observations allow us to suggest that the IMF By-related electric field can penetrate into the closed magnetosphere and produce convection and FAC changes in the region of the postnoon auroral oval. Secondly, we suggest that the interchange instability is a promising mechanism for the postnoon auroras.

  2. Energetic Electron Injections Deep Into the Inner Magnetosphere: A Result of the Subauroral Polarization Stream (SAPS) Potential Drop

    NASA Astrophysics Data System (ADS)

    Lejosne, Solène; Kunduri, B. S. R.; Mozer, F. S.; Turner, D. L.

    2018-05-01

    It has been reported that the dynamics of energetic (tens to hundreds of keV) electrons and ions is inconsistent with the theoretical picture in which the large-scale electric field is a superposition of corotation and convection electric fields. Combining one year of measurements by the Super Dual Auroral Radar Network, DMSP F-18, and the Van Allen Probes, we show that subauroral polarization streams (SAPSs) are observed when energetic electrons have penetrated below L = 4. Outside the plasmasphere in the premidnight region, potential energy is subtracted from the total energy of ions and added to the total energy of electrons during SAPS onset. This potential energy is converted into radial motion as the energetic particles drift around Earth and leave the SAPS azimuthal sector. As a result, energetic electrons are injected deeper than energetic ions when SAPSs are included in the large-scale electric field picture, in line with observations.

  3. Theoretical and experimental studies relevant to interpretation of auroral emissions

    NASA Technical Reports Server (NTRS)

    Keffer, Charles E.

    1992-01-01

    The results obtained in the second year of a three year collaborative effort with MSFC are summarized. A succession of experimental studies was completed to determine the effects of the natural and induced space vehicle environment on the measurement of auroral images from space-based platforms. In addition, a global model which incorporates both auroral and dayglow emission sources is being developed to allow interpretation of measured auroral emissions. A description of work completed on these two tasks is presented.

  4. Examination of Cross-Scale Coupling During Auroral Events using RENU2 and ISINGLASS Sounding Rocket Data.

    NASA Astrophysics Data System (ADS)

    Kenward, D. R.; Lessard, M.; Lynch, K. A.; Hysell, D. L.; Hampton, D. L.; Michell, R.; Samara, M.; Varney, R. H.; Oksavik, K.; Clausen, L. B. N.; Hecht, J. H.; Clemmons, J. H.; Fritz, B.

    2017-12-01

    The RENU2 sounding rocket (launched from Andoya rocket range on December 13th, 2015) observed Poleward Moving Auroral Forms within the dayside cusp. The ISINGLASS rockets (launched from Poker Flat rocket range on February 22, 2017 and March 2, 2017) both observed aurora during a substorm event. Despite observing very different events, both campaigns witnessed a high degree of small scale structuring within the larger auroral boundary, including Alfvenic signatures. These observations suggest a method of coupling large-scale energy input to fine scale structures within aurorae. During RENU2, small (sub-km) scale drivers persist for long (10s of minutes) time scales and result in large scale ionospheric (thermal electron) and thermospheric response (neutral upwelling). ISINGLASS observations show small scale drivers, but with short (minute) time scales, with ionospheric response characterized by the flight's thermal electron instrument (ERPA). The comparison of the two flights provides an excellent opportunity to examine ionospheric and thermospheric response to small scale drivers over different integration times.

  5. Ground and space observations of medium frequency auroral radio emissions

    NASA Astrophysics Data System (ADS)

    Broughton, Matthew C.

    The auroral zone is a rich source of natural radio emissions that can be observed in space and at ground-level. By studying these waves, scientists can gain insight into the plasma processes that generate them and use the near-Earth space environment as a large-scale plasma physics laboratory. This thesis uses both ground-level and in situ observations to study two kinds of natural radio emissions. First, we report observations of a new kind of auroral radio emission. The waves have frequencies ranging from 1.3-2.2 MHz, bandwidths ranging from 90-272 kHz, and durations ranging from 16-355 s. Spectral analysis of the waveform data has revealed that the emission has a complex combination of at least three kinds of fine structures. For model auroral electron distributions, calculations indicate that Langmuir waves could be excited at frequencies consistent with observations. The remainder of the thesis discusses auroral medium frequency (MF) burst, an impulsive, broadband natural radio emission observed at ground-level within a few minutes of local substorm onset. LaBelle [2011] proposed that MF burst originates as Langmuir/Z-mode waves on the topside of the ionosphere that subsequently mode convert to L-mode waves and propagate to ground-level. Using continuous waveform measurements and combined observations with the Sondrestrom Incoherent Scatter Radar, we have performed two tests of this mechanism. The results of these tests are consistent with the mechanism described in LaBelle [2011]. A survey of 8,624 half-orbits of the DEMETER spacecraft has revealed 68 observations of bursty MF waves. We have compared the wave properties of these waves to those of MF burst and have found that although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground-level MF burst. Finally, we have used numerical simulations to model both the fine structure of MF burst and to estimate the attenuation the

  6. Swarm Observation of Field-Aligned Currents Associated With Multiple Auroral Arc Systems

    NASA Astrophysics Data System (ADS)

    Wu, J.; Knudsen, D. J.; Gillies, D. M.; Donovan, E. F.; Burchill, J. K.

    2017-10-01

    Auroral arcs occur in regions of upward field-aligned currents (FACs); however, the relation is not one to one, since kinetic energy of the current-carrying electrons is also important in the production of auroral luminosity. Multiple auroral arc systems provide an opportunity to study the relation between FACs and auroral brightness in detail. In this study, we have identified two types of FAC configurations in multiple parallel arc systems using ground-based optical data from the Time History of Events and Macroscale Interactions during Substorms all-sky imagers, magnetometers and electric field instruments on board the Swarm satellites. In "unipolar FAC" events, each arc is an intensification within a broad, unipolar current sheet and downward return currents occur outside of this broad sheet. In "multipolar FAC" events, multiple arc systems represent a collection of multiple up/down current pairs. By collecting 17 events with unipolar FAC and 12 events with multipolar FACs, we find that (1) unipolar FAC events occur most frequently between 20 and 21 magnetic local time and multipolar FAC events tend to occur around local midnight and within 1 h after substorm onset. (2) Arcs in unipolar FAC systems have a typical width of 10-20 km and a spacing of 25-50 km. Arcs in multipolar FAC systems are wider and more separated. (3) Upward currents with more arcs embedded have larger intensities and widths. (4) Electric fields are strong and highly structured on the edges of multiple arc system with unipolar FAC. The fact that arcs with unipolar FAC are much more highly structured than the associated currents suggests that arc multiplicity is indicative not of a structured generator deep in the magnetosphere, but rather of the magnetosphere-ionosphere coupling process.

  7. A Kp-based model of auroral boundaries

    NASA Astrophysics Data System (ADS)

    Carbary, James F.

    2005-10-01

    The auroral oval can serve as both a representation and a prediction of space weather on a global scale, so a competent model of the oval as a function of a geomagnetic index could conveniently appraise space weather itself. A simple model of the auroral boundaries is constructed by binning several months of images from the Polar Ultraviolet Imager by Kp index. The pixel intensities are first averaged into magnetic latitude-magnetic local time (MLT-MLAT) and local time bins, and intensity profiles are then derived for each Kp level at 1 hour intervals of MLT. After background correction, the boundary latitudes of each profile are determined at a threshold of 4 photons cm-2 s1. The peak locations and peak intensities are also found. The boundary and peak locations vary linearly with Kp index, and the coefficients of the linear fits are tabulated for each MLT. As a general rule of thumb, the UV intensity peak shifts 1° in magnetic latitude for each increment in Kp. The fits are surprisingly good for Kp < 6 but begin to deteriorate at high Kp because of auroral boundary irregularities and poor statistics. The statistical model allows calculation of the auroral boundaries at most MLTs as a function of Kp and can serve as an approximation to the shape and extent of the statistical oval.

  8. A Statistical Analysis of Langmuir Wave-Electron Correlations Observed by the CHARM II Auroral Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Dombrowski, M. P.; Labelle, J. W.; Kletzing, C.; Bounds, S. R.; Kaeppler, S. R.

    2014-12-01

    Langmuir-mode electron plasma waves are frequently observed by spacecraft in active plasma environments such as the ionosphere. Ionospheric Langmuir waves may be excited by the bump-on-tail instability generated by impinging beams of electrons traveling parallel to the background magnetic field (B). The Correlation of High-frequencies and Auroral Roar Measurement (CHARM II) sounding rocket was launched into a substorm at 9:49 UT on 17 February 2010, from the Poker Flat Research Range in Alaska. The primary instruments included the University of Iowa Wave-Particle Correlator (WPC), the Dartmouth High-Frequency Experiment (HFE), several charged particle detectors, low-frequency wave instruments, and a magnetometer. The HFE is a receiver system which effectively yields continuous (100% duty cycle) electric-field waveform measurements from 100 kHz to 5 MHz, and which had its detection axis aligned nominally parallel to B. The HFE output was fed on-payload to the WPC, which uses a phase-locked loop to track the incoming wave frequency with the most power, then sorting incoming electrons at eight energy levels into sixteen wave-phase bins. CHARM II encountered several regions of strong Langmuir wave activity throughout its 15-minute flight, and the WPC showed wave-lock and statistically significant particle correlation distributions during several time periods. We show results of an in-depth analysis of the CHARM II WPC data for the entire flight, including statistical analysis of correlations which show evidence of direct interaction with the Langmuir waves, indicating (at various times) trapping of particles and both driving and damping of Langmuir waves by particles. In particular, the sign of the gradient in particle flux appears to correlate with the phase relation between the electrons and the wave field, with possible implications for the wave physics.

  9. Correlated variations of UV and radio emissions during an outstanding Jovian auroral event

    NASA Technical Reports Server (NTRS)

    Prange, R.; Zarka, P.; Ballester, G. E.; Livengood, T. A.; Denis, L.; Carr, T.; Reyes, F.; Bame, S. J.; Moos, H. W.

    1993-01-01

    An exceptional Jovian aurora was detected in the FUV on December 21, 1990, by means of Vilspa and Goddard Space Flight Center (GFSC) International Ultraviolet Explorer (IUE) observations. This event included intensification by a factor of three between December 20 and 21, leading to the brightest aurora identified in the IUE data analyzed, and, in the north, to a shift of the emission peak towards larger longitudes. The Jovian radio emission simultaneously recorded at decameter wavelengths in Nancay also exhibits significant changes, from a weak and short-duration emission on December 20 to a very intense one, lasting several hours, on December 21. Confirmation of this intense radio event is also found in the observations at the University of Florida on December 21. The emissions are identified as right-handed Io-independent 'A' (or 'non Io-A') components from the northern hemisphere. The radio source region deduced from the Nancay observations lies, for both days, close to the UV peak emission, exhibiting in particular a similar shift of the source region toward larger longitudes from one day to the next. A significant broadening of the radio source was also observed and it is shown that on both days, the extent of the radio source closely followed the longitude range for which the UV brightness exceeds a given threshold. The correlated variations, both in intensity and longitude, strongly suggest that a common cause triggered the variation of the UV and radio emissions during this exceptional event. On one hand, the variation of the UV aurora could possibly be interpreted according to the Prange and Elkhamsi (1991) model of diffuse multicomponent auroral precipitation (electron and ion): it would arise from an increase in the precipitation rate of ions together with an inward shift of their precipitation locus from L approximately equal 10 to L approximately equal 6. On the other hand, the analysis of Ulysses observations in the upstream solar wind suggests that

  10. Dawn- Dusk Auroral Oval Oscillations Associated with High- Speed Solar Wind

    NASA Technical Reports Server (NTRS)

    Liou, Kan; Sibeck, David G.

    2018-01-01

    We report evidence of global-scale auroral oval oscillations in the millihertz range, using global auroral images acquired from the Ultraviolet Imager on board the decommissioned Polar satellite and concurrent solar wind measurements. On the basis of two events (15 January 1999 and 6 January 2000) studied, it is found that (1) quasi-periodic auroral oval oscillations (approximately 3 megahertz) can occur when solar wind speeds are high at northward or southward interplanetary magnetic field turning, (2) the oscillation amplitudes range from a few to more than 10 degrees in latitudes, (3) the oscillation frequency is the same for each event irrespective of local time and without any azimuthal phase shift (i.e., propagation), (4) the auroral oscillations occur in phase within both the dawn and dusk sectors but 180 degrees out of phase between the dawn and dusk sectors, and (5) no micropulsations on the ground match the auroral oscillation periods. While solar wind conditions favor the growth of the Kelvin-Helmholtz (K-H) instability on the magnetopause as often suggested, the observed wave characteristics are not consistent with predictions for K-H waves. The in-phase and out-of-phase features found in the dawn-dusk auroral oval oscillations suggest that wiggling motions of the magnetotail associated with fast solar winds might be the direct cause of the global-scale millihertz auroral oval oscillations. Plain Language Summary: We utilize global auroral image data to infer the motion of the magnetosphere and show, for the first time, the entire magnetospheric tail can move east-west in harmony like a windsock flapping in wind. The characteristic period of the flapping motion may be a major source of global long-period ULF (Ultra Low Frequency) waves, adding an extra source of the global mode ULF waves.

  11. Global MHD Modeling of Auroral Conjugacy for Different IMF Conditions

    NASA Astrophysics Data System (ADS)

    Hesse, M.; Kuznetsova, M. M.; Liu, Y. H.; Birn, J.; Rastaetter, L.

    2016-12-01

    The question whether auroral features are conjugate or not, and the search for the underlying scientific causes is of high interest in magnetospheric and ionospheric physics. Consequently, this topic has attracted considerable attention in space-based observations of auroral features, and it has inspired a number of theoretical ideas and related modeling activities. Potential contributing factors to the presence or absence of auroral conjugacy include precipitation asymmetries in case of the diffuse aurora, inter-hemispherical conductivity differences, magnetospheric asymmetries brought about by, e.g., dipole tilt, corotation, or IMF By, and, finally, asymmetries in field-aligned current generation primarily in the nightside magnetosphere. In this presentation, we will analyze high-resolution, global MHD simulations of magnetospheric dynamics, with emphasis on auroral conjugacy. For the purpose of this study, we define controlled conditions by selecting solstice times with steady solar wind input, the latter of which includes an IMF rotation from purely southward to east-westward. Conductivity models will include both auroral precipaition proxies as well as the effects of the aysmmetric daylight. We will analyze these simulations with respect to conjugacies or the lack thereof, and study the role of the effects above in determing the former.

  12. Solar wind control of auroral zone geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.; Mcpherron, R. L.; Searls, C.; Kivelson, M. G.

    1981-01-01

    Solar wind magnetosphere energy coupling functions are analyzed using linear prediction filtering with 2.5 minute data. The relationship of auroral zone geomagnetic activity to solar wind power input functions are examined, and a least squares prediction filter, or impulse response function is designed from the data. Computed impulse response functions are observed to have characteristics of a low pass filter with time delay. The AL index is found well related to solar wind energy functions, although the AU index shows a poor relationship. High frequency variations of auroral indices and substorm expansions are not predictable with solar wind information alone, suggesting influence by internal magnetospheric processes. Finally, the epsilon parameter shows a poorer relationship with auroral geomagnetic activity than a power parameter, having a VBs solar wind dependency.

  13. Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope.

    PubMed

    Nichols, J D; Badman, S V; Baines, K H; Brown, R H; Bunce, E J; Clarke, J T; Cowley, S W H; Crary, F J; Dougherty, M K; Gérard, J-C; Grocott, A; Grodent, D; Kurth, W S; Melin, H; Mitchell, D G; Pryor, W R; Stallard, T S

    2014-05-28

    We present observations of significant dynamics within two UV auroral storms observed on Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroral emission observed at the poleward boundary of a solar wind-induced auroral storm, propagating at ∼330% rigid corotation from near ∼01 h LT toward ∼08 h LT. We suggest that these are indicative of ongoing, bursty reconnection of lobe flux in the magnetotail, providing strong evidence that Saturn's auroral storms are caused by large-scale flux closure. We also discuss the later evolution of a similar storm and show that the emission maps to the trailing region of an energetic neutral atom enhancement. We thus identify the auroral form with the upward field-aligned continuity currents flowing into the associated partial ring current.

  14. Dynamic auroral storms on Saturn as observed by the Hubble Space Telescope

    PubMed Central

    Nichols, J D; Badman, S V; Baines, K H; Brown, R H; Bunce, E J; Clarke, J T; Cowley, S W H; Crary, F J; Dougherty, M K; Gérard, J-C; Grocott, A; Grodent, D; Kurth, W S; Melin, H; Mitchell, D G; Pryor, W R; Stallard, T S

    2014-01-01

    We present observations of significant dynamics within two UV auroral storms observed on Saturn using the Hubble Space Telescope in April/May 2013. Specifically, we discuss bursts of auroral emission observed at the poleward boundary of a solar wind-induced auroral storm, propagating at ∼330% rigid corotation from near ∼01 h LT toward ∼08 h LT. We suggest that these are indicative of ongoing, bursty reconnection of lobe flux in the magnetotail, providing strong evidence that Saturn's auroral storms are caused by large-scale flux closure. We also discuss the later evolution of a similar storm and show that the emission maps to the trailing region of an energetic neutral atom enhancement. We thus identify the auroral form with the upward field-aligned continuity currents flowing into the associated partial ring current. PMID:26074636

  15. 24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

    NASA Technical Reports Server (NTRS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

    2011-01-01

    During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably

  16. The first full-resolution measurements of Auroral Medium Frequency Burst Emissions

    NASA Astrophysics Data System (ADS)

    Bunch, N. L.; Labelle, J.; Weatherwax, A.; Hughes, J.

    2008-12-01

    Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker

  17. Upwelling to Outflowing Oxygen Ions at Auroral Latitudes during Quiet Times: Exploiting a New Satellite Database

    NASA Astrophysics Data System (ADS)

    Redmon, Robert J.

    The mechanisms by which thermal O+ escapes from the top of the ionosphere and into the magnetosphere are not fully understood even with 30 years of active research. This thesis introduces a new database, builds a simulation framework around a thermospheric model and exploits these tools to gain new insights into the study of O+ ion outflows. A dynamic auroral boundary identification system is developed using Defense Meteorological Satellite Program (DMSP) spacecraft observations at 850 km to build a database characterizing the oxygen source region. This database resolves the ambiguity of the expansion and contraction of the auroral zone. Mining this new dataset, new understanding is revealed. We describe the statistical trajectory of the cleft ion fountain return flows over the polar cap as a function of activity and the orientation of the interplanetary magnetic field y-component. A substantial peak in upward moving O+ in the morning hours is discovered. Using published high altitude data we demonstrate that between 850 and 6000 km altitude, O+ is energized predominantly through transverse heating; and acceleration in this altitude region is relatively more important in the cusp than at midnight. We compare data with a thermospheric model to study the effects of solar irradiance, electron precipitation and neutral wind on the distribution of upward O+ at auroral latitudes. EUV irradiance is shown to play a dominant role in establishing a dawn-focused source population of upwelling O+ that is responsible for a pre-noon feature in escaping O+ fluxes. This feature has been corroborated by observations on platforms including the Dynamics Explorer 1 (DE-1), Polar, and Fast Auroral Snapshot SnapshoT (FAST) spacecraft. During quiet times our analysis shows that the neutral wind is more important than electron precipitation in establishing the dayside O+ upwelling distribution. Electron precipitation is found to play a relatively modest role in controlling dayside, and a

  18. Coordinated Ground and Space Measurements of Auroral Surge over South Pole.

    DTIC Science & Technology

    1988-02-01

    3y V. Coordinated Ground and Space Measurements of co an Auroral Surge over South Pole T. J. ROSENBERG and D. L. DETRICK Institute for Physical...Measurements of an Auroral Surge over South Pole 12. PERSONAL AUTHOR(S) Rosenberg, T. J., and DetrickD. L., University of Maryland; Mizera, Paul F., 13a. TYPE...premidnight auroral surge over Amundsen-Scott South Pole station. The set of near-simultaneous measurements provides an excellent opportunity to gain a

  19. Global Auroral Energy Deposition during Substorm Onset Compared with Local Time and Solar Wind IMF Conditions

    NASA Technical Reports Server (NTRS)

    Spann, J. F.; Brittnacher, M.; Fillingim, M. O.; Germany, G. A.; Parks, G. K.

    1998-01-01

    The global images made by the Ultraviolet Imager (UVI) aboard the IASTP/Polar Satellite are used to derive the global auroral energy deposited in the ionosphere resulting from electron precipitation. During a substorm onset, the energy deposited and its location in local time are compared to the solar wind IMF conditions. Previously, insitu measurements of low orbiting satellites have made precipitating particle measurements along the spacecraft track and global images of the auroral zone, without the ability to quantify energy parameters, have been available. However, usage of the high temporal, spatial, and spectral resolution of consecutive UVI images enables quantitative measurement of the energy deposited in the ionosphere not previously available on a global scale. Data over an extended period beginning in January 1997 will be presented.

  20. ANALYSIS OF ENERGY LOSSES OF A 30-kev ELECTRON BEAM IN THE FLUORIDE, CHLORIDE, AND BROMIDE OF LITHIUM (in French)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pradal, F.; Gout, C.

    1963-02-01

    The energy loss of a 30-kev electron beam in films of LiF, LiCl, and LiBr were analyzed with a magnetic spectrograph. For LiF, the results are compared to the absorption curve in the ultraviolet. The rays observed seem due to the excitation of valence band electrons of the 2s band of F/sup -/ and the 1s band of Li/sup +/. In some cases, energy losses less than 10 ev were observed, which seems connected to the presence of color centers. (tr-auth)

  1. IUE observations of longitudinal and temporal variations in the Jovian auroral emission

    NASA Technical Reports Server (NTRS)

    Skinner, T. E.; Durrance, S. T.; Feldman, P. D.; Moos, H. W.

    1984-01-01

    The IUE's short wavelength spectrograph has been used to monitor the auroral emissions from Jupiter's northern hemisphere, yielding eight observations between January 1981 and January 1982 of H I Lyman-alpha and the H2 Lyman and Werner bands. Attention is given to an apparent periodic emission flux fluctuation, through detailed modeling of the emission geometry. Two possible auroral zones are defined at the north pole by mapping the magnetic field lines from the Io torus and the magnetotail onto the planet's atmosphere. The observed variation in flux with central meridian longitude is not consistent with a uniform brightness as a function of magnetic longitude in either auroral zone. The data can be fitted by confining the emissions to the region of the northern torus auroral zone, in qualitative agreement with the magnetic anomaly model. A similar emission from the magnetotail auroral zone cannot be ruled out.

  2. Global Dynamics of Dayside Auroral Precipitation in Conjunction with Solar Wind Pressure Pulses

    NASA Technical Reports Server (NTRS)

    Brittnacher, M.; Chua, D.; Fillingim, M.; Parks, G. K.; Spann, James F., Jr.; Germany, G. A.; Carlson, C. W.; Greenwald, R. A.

    1999-01-01

    Global observation of the dayside auroral region by the Ultraviolet Imager (UVI) during transient solar wind pressure pulse events on October 1, 1997 has revealed unusual features in the auroral precipitation. The auroral arc structure on the dayside, possibly connected with the LLBL, split into 2 arc structures; one moving poleward and fading over a 5 min period, and the other stationary or slightly shifted equatorward (by changes in the x component). The y component was large and positive, and the z component was small and negative. The splitting of the arc structure extended from 9 to 15 MLT and was concurrent with an enhancement of the convection in the cusp region identified by SuperDARN observations. The convection reversal on the morningside was adjacent to and poleward of the weak lower latitude band of precipitation. The sensitivity of the UVI instrument enabled observation of arc structures down to about 0.2 erg electron energy flux, as confirmed by comparison with particle measurements from the FAST satellite for other dayside events. Removal of the spacecraft wobble by PIXON image reconstruction restored the original resolution of the UVI of about 40 km from apogee. This event is being analyzed in connection with a larger study of global dynamics of dayside energy and momentum transfer related to changes in IMF conditions using UVI images in conjunction with observations from FAST and SuperDARN.

  3. Signal yields of keV electronic recoils and their discrimination from nuclear recoils in liquid xenon

    NASA Astrophysics Data System (ADS)

    Aprile, E.; Aalbers, J.; Agostini, F.; Alfonsi, M.; Amaro, F. D.; Anthony, M.; Arneodo, F.; Barrow, P.; Baudis, L.; Bauermeister, B.; Benabderrahmane, M. L.; Berger, T.; Breur, P. A.; Brown, A.; Brown, E.; Bruenner, S.; Bruno, G.; Budnik, R.; Bütikofer, L.; Calvén, J.; Cardoso, J. M. R.; Cervantes, M.; Cichon, D.; Coderre, D.; Colijn, A. P.; Conrad, J.; Cussonneau, J. P.; Decowski, M. P.; de Perio, P.; di Gangi, P.; di Giovanni, A.; Diglio, S.; Eurin, G.; Fei, J.; Ferella, A. D.; Fieguth, A.; Fulgione, W.; Gallo Rosso, A.; Galloway, M.; Gao, F.; Garbini, M.; Geis, C.; Goetzke, L. W.; Grandi, L.; Greene, Z.; Grignon, C.; Hasterok, C.; Hogenbirk, E.; Howlett, J.; Itay, R.; Kaminsky, B.; Kazama, S.; Kessler, G.; Kish, A.; Landsman, H.; Lang, R. F.; Lellouch, D.; Levinson, L.; Lin, Q.; Lindemann, S.; Lindner, M.; Lombardi, F.; Lopes, J. A. M.; Mahlstedt, J.; Manfredini, A.; Maris, I.; Marrodán Undagoitia, T.; Masbou, J.; Massoli, F. V.; Masson, D.; Mayani, D.; Messina, M.; Micheneau, K.; Molinario, A.; Morâ, K.; Murra, M.; Naganoma, J.; Ni, K.; Oberlack, U.; Pakarha, P.; Pelssers, B.; Persiani, R.; Piastra, F.; Pienaar, J.; Pizzella, V.; Piro, M.-C.; Plante, G.; Priel, N.; Ramírez García, D.; Rauch, L.; Reichard, S.; Reuter, C.; Rizzo, A.; Rupp, N.; Saldanha, R.; Dos Santos, J. M. F.; Sartorelli, G.; Scheibelhut, M.; Schindler, S.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Selvi, M.; Shagin, P.; Shockley, E.; Silva, M.; Simgen, H.; Sivers, M. V.; Stein, A.; Thers, D.; Tiseni, A.; Trinchero, G.; Tunnell, C.; Vargas, M.; Wang, H.; Wang, Z.; Wei, Y.; Weinheimer, C.; Wittweg, C.; Wulf, J.; Ye, J.; Zhang, Y.; Zhu, T.; Xenon Collaboration

    2018-05-01

    We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of 92 V /cm , 154 V /cm and 366 V /cm using the XENON100 detector. A data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366 V /cm are presented. The electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. The results provide new measurements in the energy region of interest for dark matter searches using liquid xenon.

  4. Influence of interplanetary magnetic field and solar wind on auroral brightness in different regions

    NASA Astrophysics Data System (ADS)

    Yang, Y. F.; Lu, J. Y.; Wang, J.-S.; Peng, Z.; Zhou, L.

    2013-01-01

    Abstract<p label="1">By integrating and averaging the <span class="hlt">auroral</span> brightness from Polar Ultraviolet Imager <span class="hlt">auroral</span> images, which have the whole <span class="hlt">auroral</span> ovals, and combining the observation data of interplanetary magnetic field (IMF) and solar wind from NASA Operating Missions as a Node on the Internet (OMNI), we investigate the influence of IMF and solar wind on <span class="hlt">auroral</span> activities, and analyze the separate roles of the solar wind dynamic pressure, density, and velocity on aurora, respectively. We statistically analyze the relations between the interplanetary conditions and the <span class="hlt">auroral</span> brightness in dawnside, dayside, duskside, and nightside. It is found that the three components of the IMF have different effects on the <span class="hlt">auroral</span> brightness in the different regions. Different from the nightside <span class="hlt">auroral</span> brightness, the dawnside, dayside, and duskside <span class="hlt">auroral</span> brightness are affected by the IMF Bx, and By components more significantly. The IMF Bx and By components have different effects on these three regional <span class="hlt">auroral</span> brightness under the opposite polarities of the IMF Bz. As expected, the nightside aurora is mainly affected by the IMF Bz, and under southward IMF, the larger the |Bz|, the brighter the nightside aurora. The IMF Bx and By components have no visible effects. On the other hand, it is also found that the aurora is not intensified singly with the increase of the solar wind dynamic pressure: when only the dynamic pressure is high, but the solar wind velocity is not very fast, the aurora will not necessarily be intensified significantly. These results can be used to qualitatively predict the <span class="hlt">auroral</span> activities in different regions for various interplanetary conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DPS....4731113S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DPS....4731113S"><span>Jupiter's <span class="hlt">auroral</span>-related thermal infrared emission from IRTF-TEXES</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinclair, James; Orton, Glenn; Greathouse, Thomas; Fletcher, Leigh; Irwin, Patrick</p> <p>2015-11-01</p> <p><span class="hlt">Auroral</span> processes on Jupiter can be observed at a large range of wavelengths. Charged particles of the solar wind are deflected by Jupiter’s magnetic field and penetrate the atmosphere at high latitudes. This results in ion and/or <span class="hlt">electron</span> precipitation, which produces emission at X-ray, UV, visible, near-infrared and even radio wavelengths. These observations indicate three distinct features of the aurora: 1) filament-like oval structures fixed at the magnetic poles (~80°W (System III) in the south, ~180°W in the north), 2) spatially-continuous but transient aurora that fill these oval regions and 3) discrete spots associated with the magnetic footprints of Io and other Galilean satellites. However, observations in the thermal infrared indicate the aurora also modify the neutral atmosphere. Enhanced emission of CH4 is observed coincident with the <span class="hlt">auroral</span> ovals and indicates heightened stratospheric temperatures possibly as a result of joule heating by the influx of charged particles. Stronger emission is also observed of C2H2, C2H4, C2H6 and even C6H6 though previous work has struggled to determine whether this is a temperature or compositional effect. In order to quantify the <span class="hlt">auroral</span> effects on the neutral atmosphere and to support the 2016 Juno mission (which has no thermal infrared instrument) we have performed a retrieval analysis of IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph, 5- to 25-μm) spectra obtained on Dec 11th 2014 near solar maximum. The instrument slit was scanned east-west across high latitudes in each hemisphere and Jupiter’s rotation was used to obtain ~360° longitudinal coverage. Spectra of H2 S(1), CH4, C2H2, C2H4 and C2H6 emission were measured at a resolving power of R = 85000, allowing a large vertical range in the atmosphere (100 - 0.001 mbar) to be sounded. Preliminary retrievals of the vertical temperature profile from H2 S(1) and CH4 measurements at 60°N, 180°W (on aurora), in comparison to 60°N, 60°W (quiescent</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790016401','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790016401"><span><span class="hlt">Auroral</span> magnetosphere-ionosphere coupling: A brief topical review</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chiu, Y. T.; Schulz, M.; Cornwall, J. M.</p> <p>1979-01-01</p> <p><span class="hlt">Auroral</span> arcs result from the acceleration and precipitation of magnetospheric plasma in narrow regions characterized by strong electric fields both perpendicular and parallel to the earth's magnetic field. The various mechanisms that were proposed for the origin of such strong electric fields are often complementary Such mechanisms include: (1) electrostatic double layers; (2) double reverse shock; (3) anomalous resistivity; (4) magnetic mirroring of hot plasma; and (5) mapping of the magnetospheric-convection electric field through an <span class="hlt">auroral</span> discontinuity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.9543Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.9543Z"><span>Characteristics of pitch angle distributions of hundreds of <span class="hlt">keV</span> <span class="hlt">electrons</span> in the slot region and inner radiation belt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, H.; Li, X.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Baker, D. N.; Jaynes, A. N.; Malaspina, D. M.</p> <p>2014-12-01</p> <p>The pitch angle distribution (PAD) of energetic <span class="hlt">electrons</span> in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state-of-the-art pitch angle-resolved data from the Magnetic <span class="hlt">Electron</span> Ion Spectrometer instrument onboard the Van Allen Probes, a detailed analysis of hundreds of <span class="hlt">keV</span> <span class="hlt">electron</span> PADs below L = 4 is performed, in which the PADs are categorized into three types: normal (flux peaking at 90°), cap (exceedingly peaking narrowly around 90°), and 90° minimum (lower flux at 90°) PADs. By examining the characteristics of the PADs of ˜460 <span class="hlt">keV</span> <span class="hlt">electrons</span> for over a year, we find that the 90° minimum PADs are generally present in the inner belt (L<2), while normal PADs dominate at L˜3.5-4. In the region between, 90° minimum PADs dominate during injection times and normal PADs dominate during quiet times. Cap PADs appear mostly at the decay phase of storms in the slot region and are likely caused by the pitch angle scattering of hiss waves. Fitting the normal PADs into sinnα form, the parameter n is much higher below L = 3 than that in the outer belt and relatively constant in the inner belt but changes significantly in the slot region (2 < L < 3) during injection times. As for the 90° minimum PADs, by performing a detailed case study, we find in the slot region this type of PAD is likely caused by chorus wave heating, but this mechanism can hardly explain the formation of 90° minimum PADs at the center of inner belt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080037609&hterms=solar+intensity+measurement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsolar%2Bintensity%2Bmeasurement','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080037609&hterms=solar+intensity+measurement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsolar%2Bintensity%2Bmeasurement"><span>Saturn's <span class="hlt">Auroral</span> Response to the Solar Wind: Centrifugal Instability Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sittler, Edward C.; Blanc, Michel F.; Richardson, J. D.</p> <p>2008-01-01</p> <p>We describe a model initially presented by Sittler et al. [2006] which attempts to explain the global response of Saturn's magnetosphere and its corresponding <span class="hlt">auroral</span> behavior to variations in the solar wind. The model was derived from published simultaneous Hubble Space Telescope (HST) <span class="hlt">auroral</span> images and Cassini upstream measurements taken during the month of January 2004. These observations show a direct correlation between solar wind dynamic pressure and (1) <span class="hlt">auroral</span> brightening toward dawn local time, (2) an increase of rotational movement of <span class="hlt">auroral</span> features to as much as 75% of the corotation speed, (3) the movement of the <span class="hlt">auroral</span> oval to higher latitudes and (4) an increase in the intensity of Saturn Kilometric Radiation (SKR). This model is an alternative to the reconnection model of Cowley et al. [2004a,b; 2005] which is more Earth-like while ours stresses rotation. If angular momentum is conserved in a global sense, then when compressed the magnetosphere will tend to spin up and when it expands will tend to spin down. With the plasma sheet outer boundary at L approximates 15 we argue this region to be the dominant source region for the precipitating particles. If radial transport is dominated by centrifugal driven flux tube interchange motions, then when the magnetosphere spins up, outward transport will increase, the precipitating particles will move radially outward and cause the <span class="hlt">auroral</span> oval to move to higher latitudes as observed. The Kelvin-Helmholtz instability may contribute to the enhanced emission along the dawn meridian as observed by HST. We present this model in the context of presently published observations by Cassini.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.3668C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.3668C"><span>Mapping <span class="hlt">auroral</span> activity with Twitter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Case, N. A.; MacDonald, E. A.; Heavner, M.; Tapia, A. H.; Lalone, N.</p> <p>2015-05-01</p> <p>Twitter is a popular, publicly accessible, social media service that has proven useful in mapping large-scale events in real time. In this study, for the first time, the use of Twitter as a measure of <span class="hlt">auroral</span> activity is investigated. Peaks in the number of aurora-related tweets are found to frequently coincide with geomagnetic disturbances (detection rate of 91%). Additionally, the number of daily aurora-related tweets is found to strongly correlate with several <span class="hlt">auroral</span> strength proxies (ravg≈0.7). An examination is made of the bias for location and time of day within Twitter data, and a first-order correction of these effects is presented. Overall, the results suggest that Twitter can provide both specific details about an individual aurora and accurate real-time indication of when, and even from where, an aurora is visible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RaPC..107..199S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RaPC..107..199S"><span><span class="hlt">Electron</span> density of Rhizophora spp. wood using Compton scattering technique at 15.77, 17.48 and 22.16 <span class="hlt">keV</span> XRF energies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shakhreet, B. Z.; Bauk, S.; Shukri, A.</p> <p>2015-02-01</p> <p>Compton (incoherently) scattered photons which are directly proportional to the <span class="hlt">electron</span> density of the scatterer, have been employed in characterizing Rhizophora spp. as breast tissue equivalent. X-ray fluorescent scattered incoherently from Rhizophora spp. sample was measured using Si-PIN detector and three XRF energy values 15.77, 17.48 and 22.16 <span class="hlt">keV</span>. This study is aimed at providing <span class="hlt">electron</span> density information in support of the introduction of new tissue substitute materials for mammography phantoms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM51C2190S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM51C2190S"><span>The Search for Precursor Redline <span class="hlt">Auroral</span> Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sobel, E. I.; Kepko, L.; Angelopoulos, V.; Donovan, E.; Spanswick, E.</p> <p>2013-12-01</p> <p>A popular theory of geomagnetic substorms postulates that substorms begin in the downtail region of the magnetosphere and propagate Earthward. This should result in a visible <span class="hlt">auroral</span> precursor; however, observations have not shown such formations. This poster presents the results of our project to examine the little-studied redline data in search of these early-cycle <span class="hlt">auroral</span> phenomena. We reviewed daily ground-based redline <span class="hlt">auroral</span> observations for relevant months of 2008-2013 using software developed in IDL and created an event database with the observation stations, onset timestamp, available satellites, and notes. After narrowing the initial list of nearly 350 events to the best 5, we analyzed the redline events alongside white light and green light observations from the same stations, as well as in situ measurements from THEMIS and geomagnetic readings from ground-based stations. Preliminary results from 36 suspected cases and 5 confirmed cases show some instances of clear redline formations that precede visual onsets. These phenomena form above the equatorward <span class="hlt">auroral</span> arc, descend over several minutes, and then appear to trigger onset within minutes of reaching the arc boundary. We also found evidence that these precursors are created by earthward plasma flows. This research helps answer the long-standing question of why there has been no visible precursor, despite strong evidence of pre-onset earthward flows. It is one of the first ventures into the lower spectra of the aurora, opening the door for future work on the longer-lasting, lower-energy, and more sensitive red wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA44A..01N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA44A..01N"><span>Mesoscale thermospheric wind in response to nightside <span class="hlt">auroral</span> brightening</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nishimura, T.; Zou, Y.; Gabrielse, C.; Lyons, L. R.; Varney, R. H.; Conde, M.; Hampton, D. L.; Mende, S. B.</p> <p>2017-12-01</p> <p>Although high-latitude ionospheric flows and thermospheric winds in the F-region are overall characterized by two-cell patterns over a global scale ( 1000 km), intense energy input from the magnetosphere often occurs in a mesoscale ( 100 km) and transient manner ( 10 min). Intense mesoscale energy input would drive enhanced mesoscale winds, whose properties are closely associated with <span class="hlt">auroral</span> arcs and associated ionospheric flows. However, how thermospheric winds respond to and distribute around mesoscale magnetospheric input has not been characterized systematically. This presentation addresses how mesoscale winds distribute around quasi-steady arcs, evolve and distribute around transient arcs, and vary with geomagnetic and solar activity. We use Scanning Doppler Imagers (SDIs), all-sky imagers and PFISR over Alaska. A channel of azimuthal neutral wind is often found associated with localized flow channels adjacent to quasi-steady discrete aurora. The wind speed dynamically changes after a short time lag (a few tens of minutes) from <span class="hlt">auroral</span> brightenings, including <span class="hlt">auroral</span> streamers and intensifications on preexisting <span class="hlt">auroral</span> arcs. This is in contrast to a much longer time lag ( 1 hour) reported previously. During a storm main phase, a coherent equatorward motion of the Harang discontinuity was seen in plasma flow, aurora and neutral wind, with a few degrees of equatorward displacement of the neutral wind Harang, which is probably due to the inertia. These results suggest that a tight M-I-T connection exists under the energy input of assorted <span class="hlt">auroral</span> arcs and that mesoscale coupling processes are important in M-I-T energy transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EOSTr..94..273S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EOSTr..94..273S"><span><span class="hlt">Auroral</span> Phenomenology and Magnetospheric Processes: Earth and Other Planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schultz, Colin</p> <p>2013-07-01</p> <p>The dancing glow of the aurorae, the long tendrils of light that seem to reach up into space, has mesmerized scientists for centuries. More than a beautiful display, the aurorae tell us about the Earth—about its atmosphere, its magnetic field, and its relationship with the Sun. As technology developed, researchers looking beyond Earth's borders discovered an array of <span class="hlt">auroral</span> processes on planets throughout the solar system. In the AGU monograph <span class="hlt">Auroral</span> Phenomenology and Magnetospheric Processes: Earth and Other Planets, editors Andreas Keiling, Eric Donovan, Fran Bagenal, and Tomas Karlsson explore the many open questions that permeate the science of <span class="hlt">auroral</span> physics and the relatively recent field of extraterrestrial aurorae. In this interview, Eos talks to Karlsson about extraterrestrial aurorae, Alfvén waves, and the sounds of the northern lights.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030061175&hterms=Ford&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DFord','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030061175&hterms=Ford&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DFord"><span>Preliminary Results from Recent Simultaneous Chandra/HST Observations of Jupiter <span class="hlt">Auroral</span> Zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Elsner, R.; Gladstone, R.; Waite, H.; Majeed, T.; Ford, P.; Grodent, D.; Bwardwaj, A.; Howell, R.; Cravens, T.; MacDowell, R.</p> <p>2003-01-01</p> <p>Jupiter was observed by the Chandra X-ray Observatory in late February, 2003, for 144 ks, using both the ACIS-S and HRC-I imaging x-ray cameras. Five orbits of HST STIS observations of the planet's northern <span class="hlt">auroral</span> zone were obtained during the ACIS-S observations. These data are providing a wealth of information about Jupiter's <span class="hlt">auroral</span> activity, including the first x-ray spectra from the x-ray hot spots inside the <span class="hlt">auroral</span> ovals. We will also discuss the approximately 45 minute quasi-periodicity in the <span class="hlt">auroral</span> x-ray emission - which correlates well with simultaneous observations of radio bursts by the Ulysses spacecraft - and a possible phase relation between the emission from the northern and southern x-ray aurora.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820028333&hterms=1087&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231087','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820028333&hterms=1087&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231087"><span>Correlations between solar wind parameters and <span class="hlt">auroral</span> kilometric radiation intensity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gallagher, D. L.; Dangelo, N.</p> <p>1981-01-01</p> <p>The relationship between solar wind properties and the influx of energy into the nightside <span class="hlt">auroral</span> region as indicated by the intensity of <span class="hlt">auroral</span> kilometric radiation is investigated. Smoothed Hawkeye satellite observations of <span class="hlt">auroral</span> radiation at 178, 100 and 56.2 kHz for days 160 through 365 of 1974 are compared with solar wind data from the composite Solar Wind Plasma Data Set, most of which was supplied by the IMP-8 spacecraft. Correlations are made between smoothed daily averages of solar wind ion density, bulk flow speed, total IMF strength, electric field, solar wind speed in the southward direction, solar wind speed multiplied by total IMF strength, the substorm parameter epsilon and the Kp index. The greatest correlation is found between solar wind bulk flow speed and <span class="hlt">auroral</span> radiation intensity, with a linear correlation coefficient of 0.78 for the 203 daily averages examined. A possible mechanism for the relationship may be related to the propagation into the nightside magnetosphere of low-frequency long-wavelength electrostatic waves produced in the magnetosheath by the solar wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..12212406G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..12212406G"><span>Influence of <span class="hlt">Auroral</span> Streamers on Rapid Evolution of Ionospheric SAPS Flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallardo-Lacourt, Bea; Nishimura, Y.; Lyons, L. R.; Mishin, E. V.; Ruohoniemi, J. M.; Donovan, E. F.; Angelopoulos, V.; Nishitani, N.</p> <p>2017-12-01</p> <p>Subauroral polarization streams (SAPS) often show large, rapid enhancements above their slowly varying component. We present simultaneous observations from ground-based all-sky imagers and flows from the Super Dual <span class="hlt">Auroral</span> Radar Network radars to investigate the relationship between <span class="hlt">auroral</span> phenomena and flow enhancement. We first identified <span class="hlt">auroral</span> streamers approaching the equatorward boundary of the <span class="hlt">auroral</span> oval to examine how often the subauroral flow increased. We also performed the reverse query starting with subauroral flow enhancements and then evaluated the <span class="hlt">auroral</span> conditions. In the forward study, 98% of the streamers approaching the equatorward boundary were associated with SAPS flow enhancements reaching 700 m/s and typically hundreds of m/s above background speeds. The reverse study reveals that flow enhancements associated with streamers (60%) and enhanced larger-scale convection (37%) contribute to SAPS flow enhancements. The strong correlation of <span class="hlt">auroral</span> streamers with rapid evolution (approximately minutes) of SAPS flows suggests that transient fast earthward plasma sheet flows can often lead to westward SAPS flow enhancements in the subauroral region and that such enhancements are far more common than only during substorms because of the much more frequent occurrences of streamers under various geomagnetic conditions. We also found a strong correlation between flow duration and streamer duration and a weak correlation between SAPS flow velocity and streamer intensity. This result suggests that intense flow bursts in the plasma sheet (which correlate with intense streamers) are associated with intense SAPS ionospheric flows perhaps by enhancing the ring current pressure and localized pressure gradients when they are able to penetrate close enough to Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JGRA..108.8007S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JGRA..108.8007S"><span>Double layers in expanding plasmas and their relevance to the <span class="hlt">auroral</span> plasma processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, Nagendra; Khazanov, George</p> <p>2003-04-01</p> <p>When a dense plasma consisting of a cold and a sufficiently warm <span class="hlt">electron</span> population expands, a rarefaction shock forms [, 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm <span class="hlt">electron</span> population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the <span class="hlt">auroral</span> acceleration of <span class="hlt">electrons</span> and ions in the upward current region [, 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold <span class="hlt">electron</span> populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold <span class="hlt">electrons</span> coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot <span class="hlt">electron</span> temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve <span class="hlt">electron</span>-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The <span class="hlt">electron-electron</span> two-stream interactions on the high-potential side of the RFS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM51C2508K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM51C2508K"><span>Cusp <span class="hlt">Electron</span> Populations During a Neutral Upwelling Event: Measurements from RENU2 and MMS Conjunction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kenward, D. R.; Lessard, M.; Lynch, K. A.; Hysell, D. L.; Hecht, J. H.; Clemmons, J. H.; Crowley, G.; Cohen, I. J.; Sigernes, F.; Oksavik, K.; Yeoman, T. K.; Lee, S. H.; Burch, J. L.</p> <p>2016-12-01</p> <p>The Rocket Experiment for Neutral Upwelling (RENU2) NASA sounding rocket mission launched into the dayside cusp region from the Andøya Space Center at 07:34 UT on 13 December 2015. The <span class="hlt">Electron</span> Plasma (EPLAS) instrument provided by University of New Hampshire measured the energy distribution of <span class="hlt">electrons</span> from 10 eV to 15 <span class="hlt">keV</span> in 1 ms time steps. This allowed for measurements of small-scale structures within the Poleward Moving <span class="hlt">Auroral</span> Forms (PMAFs) observed by RENU2. In addition, EPLAS had a 360 degree field of view with 10 degree angular resolution to record pitch angle information of the precipitating <span class="hlt">electron</span> population. This presentation reports the details and results of a new algorithm developed to define the field-aligned (FA) <span class="hlt">electron</span> population and determine the precipitating energy flux. <span class="hlt">Electron</span> energy spectra observations from the rocket are presented along with simultaneous particle and field observations from the Magnetospheric Multiscale (MMS) spacecraft at the dayside magnetopause. This conjunction between RENU2 and MMS presents a unique and ideal opportunity to study the in situ dynamics of magnetosphere-ionosphere coupling in the cusp along with dayside reconnection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160007821','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160007821"><span>Spacecraft Charging and <span class="hlt">Auroral</span> Boundary Predictions in Low Earth Orbit</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Minow, Joseph I.</p> <p>2016-01-01</p> <p><span class="hlt">Auroral</span> charging of spacecraft is an important class of space weather impacts on technological systems in low Earth orbit. In order for space weather models to accurately specify <span class="hlt">auroral</span> charging environments, they must provide the appropriate plasma environment characteristics responsible for charging. Improvements in operational space weather prediction capabilities relevant to charging must be tested against charging observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA51B2392M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA51B2392M"><span>Association between substorm onsets in <span class="hlt">auroral</span> all-sky images and geomagnetic Pi2pulsations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miura, T.; Ieda, A.; Teramoto, M.; Kawashima, T.</p> <p>2017-12-01</p> <p>Substorms are explosive disturbances in the magnetosphere and ionosphere of Earth. Substorm onsets are often identified usingsudden <span class="hlt">auroral</span> brightenings (<span class="hlt">auroral</span> breakup) or geomagnetic Pi2 pulsations. These <span class="hlt">auroral</span> brightenings and Pi2 pulsations aresupposed to occur simultaneously within approximately 1 min of each other. However, as <span class="hlt">auroral</span> brightenings typically includea two-stage development, this simultaneity is not straightforward. In this study, we clarify the correspondence between Pi2 pulsations and <span class="hlt">auroral</span> brightenings, including the two-stage development.The first stage of the development is the sudden brightening of an <span class="hlt">auroral</span> arc near the midnight (initial brightening)and the second stage is the poleward expansion of the <span class="hlt">auroral</span> arc. We compared all-sky images (3 s resolution) in Canada andgeomagnetic observations (0.5-1 s resolution) in North and Central America, using data from the THEMIS project. In this study,we examined three substorms events that exhibit evidence of the two-stage <span class="hlt">auroral</span> development. In the first event (4 March 2008), an <span class="hlt">auroral</span> initial brightening occurred at 0533:57 UT and a poleward expansion was observedat 0538:12 UT (4 min after the initial brightening) in Gillam (magnetic latitude:66.0 °, longitude:333 °, MLT:22.9). In contract,the Pi2 pulsation started at 0539:30 UT, which is closer to the time of the poleward expansion, in Carson City (magnetic latitude:45.0 °, longitude:304 °). and San Juan (magnetic latitude:27.9 °, longitude:6.53 °). Thus, we consider this Pi2 pulsation ascorresponding to the poleward expansion rather than the initial brightening. This correspondence was also seen in the other twoevents, suggesting that it is not exceptional. We interpret that the Pi2 pulsation corresponds to the poleward expansion becauseboth are caused by the magnetic field dipolarization, which is a drastic change that propagates from low- to high-latitude fieldlines.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSA42A..06K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSA42A..06K"><span>Defense Meteorological Satellite Program Data in Dynamic <span class="hlt">Auroral</span> Boundary Coordinates: New insights into Polar Cap and <span class="hlt">Auroral</span> Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knipp, D.</p> <p>2016-12-01</p> <p>Using reprocessed (Level-2) data from the Defense Meteorology Satellite Program magnetometer (SSM) and particle precipitation (SSJ) instruments we determine the boundaries of the central plasma sheet <span class="hlt">auroral</span> oval, and then consider the relative locations and intensities of field aligned currents. Large-scale field-aligned currents (FAC) are determined using the Minimum Variance Analysis technique, and their influence is then removed from the magnetic perturbations allowing us to estimate intensity and scale-size of the smaller-scale currents. When sorted by dynamic <span class="hlt">auroral</span> boundary coordinates we find that large- scale Region 1 (R1) FAC are often within the polar cap and Region 2 (R2) FAC show a strong dawn-dusk asymmetry (as in Ohtani et al., 2010). We find that mesoscale FAC are stronger in the summer and are most consistently present in the vicinity of dawnside (downward) R1 FAC. Further, mesoscale FAC are confined to <span class="hlt">auroral</span> latitudes and above on the dawnside, but can be subaroural on the dusk side. Hotspots of mesoscale FAC occur in pre-midnight regions especially during summer. Finally, we show how this information can be combined with measurements from above and below the ionosphere-thermosphere to help explain significant perturbations in polar cap dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GI......7..113Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GI......7..113Y"><span>A comparative study of <span class="hlt">auroral</span> morphology distribution between the Northern and Southern Hemisphere based on automatic classification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Qiuju; Hu, Ze-Jun</p> <p>2018-03-01</p> <p>Aurora is a very important geophysical phenomenon in the high latitudes of Arctic and Antarctic regions, and it is important to make a comparative study of the <span class="hlt">auroral</span> morphology between the two hemispheres. Based on the morphological characteristics of the four labeled dayside discrete <span class="hlt">auroral</span> types (<span class="hlt">auroral</span> arc, drapery corona, radial corona and hot-spot aurora) on the 8001 dayside <span class="hlt">auroral</span> images at the Chinese Arctic Yellow River Station in 2003, and by extracting the local binary pattern (LBP) features and using a k-nearest classifier, this paper performs an automatic classification of the 65 361 <span class="hlt">auroral</span> images of the Chinese Arctic Yellow River Station during 2004-2009 and the 39 335 <span class="hlt">auroral</span> images of the South Pole Station between 2003 and 2005. Finally, it obtains the occurrence distribution of the dayside <span class="hlt">auroral</span> morphology in the Northern and Southern Hemisphere. The statistical results indicate that the four dayside discrete <span class="hlt">auroral</span> types present a similar occurrence distribution between the two stations. To the best of our knowledge, we are the first to report statistical comparative results of dayside <span class="hlt">auroral</span> morphology distribution between the Northern and Southern Hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018P%26SS..155...91G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018P%26SS..155...91G"><span>0.2 to 10 <span class="hlt">keV</span> <span class="hlt">electrons</span> interacting with water ice: Radiolysis, sputtering, and sublimation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galli, A.; Vorburger, A.; Wurz, P.; Pommerol, A.; Cerubini, R.; Jost, B.; Poch, O.; Tulej, M.; Thomas, N.</p> <p>2018-06-01</p> <p>We present new laboratory experiments investigating various water ice samples, ranging from thin ice films to porous thick ice layers, that are irradiated with <span class="hlt">electrons</span>. The molecules leaving the ice are monitored with a pressure gauge and a mass spectrometer. Most particles released from the ice are H2 and O2, the observed ratio of 2:1 is consistent with H2O being radiolysed into H2 + 1/2 O2 upon irradiation. H2O2 is likely a minor contribution of radiolysis, amounting to 0.001 ± 0.001 of the total gas release from the ice sample. Neither the physical properties of the ice, nor the energy, nor the <span class="hlt">electron</span> impact angle have any obvious effect on the relative abundances of the radiolysis products. The absolute sputtering yield (i.e., the ratio of produced O2 or destroyed H2O per impacting <span class="hlt">electron</span>) increases with energy until a few 100 eV. For higher energies up to 10 <span class="hlt">keV</span> the yield remains roughly constant, once the saturation dose of the ice is reached. This indicates that ongoing irradiation eventually releases the radiolysis products from the water ice even for penetration depths of several micrometers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040027570&hterms=thermodynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dthermodynamics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040027570&hterms=thermodynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dthermodynamics"><span>Ground Based Remote Sensing of Upper Atmosphere Dynamics, Thermodynamics and Composition in Support of TIMED Satellites Scientific Mission</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p>The following research work was accomplished: 1. We operated high throughput spectrophotometers and interferometers at eight observatories in the Arctic, Antarctic and mid-latitude regions to record relatively high-resolution spectra of very low light level airglow and <span class="hlt">auroral</span> line as well as band emissions. 2. Our Polar observations of <span class="hlt">auroral</span> emissions from N2 and O emissions have been analyzed to derive the O/N2 ratios around 110 km height in the Polar thermosphere during different <span class="hlt">auroral</span> events triggered by the precipitation of <span class="hlt">auroral</span> <span class="hlt">electrons</span> with average energy of about 10 <span class="hlt">keV</span>. These results have been compared with similar ratios derived from TIMED satellite s GUVI measurements of N2 LBH and 01 1356A emissions. 3. Our airglow measurements show MLT density and temperature modulations by Planetary, Tidal and Gravity Waves. They also indicate Mesopause cooling preceding a Stratospheric Warming Event (SWE).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMSM13D..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMSM13D..03B"><span>What can we learn from the <span class="hlt">auroral</span> footprints of the Jovian moons? (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonfond, B.</p> <p>2010-12-01</p> <p>The signature of electromagnetic interaction between the moons Io, Europa and Ganymede and the Jovian magnetosphere can be observed on Jupiter’s polar ionosphere in the form of <span class="hlt">auroral</span> footprints. The observation campaigns carried out during the past few years by the Hubble Space Telescope in the Far UV domain provided not only a high spatial and temporal resolution but also an unprecedented System III longitude coverage. Consequently, these recent observations of the morphology and the dynamics of the footprints proved to be very powerful tools to probe these interactions. For example, the locations of the satellite footprints have been used as a valuable constraint for building Jovian magnetic field models. Moreover, analysis of the multiplicity of the Io footprint spots as well as their relative motion lead to new conclusions on the <span class="hlt">electron</span> acceleration processes. The altitude of the Io footprint has also been used to infer the typical energy of the impinging <span class="hlt">electrons</span>. Finally, the study of the three-dimensional shape and of the brightness of the different sub-structures of the footprints provides important clues on the processes at play between Io and the Jovian ionosphere. On the theoretical side, considerable efforts have also been recently carried out in order to model the propagation of the Alfvén waves generated at Io and the subsequent acceleration of <span class="hlt">auroral</span> <span class="hlt">electrons</span>. Coupled with HST images, radio decametric measurements and in situ data from the Galileo spacecraft, these advances provide a brand new understanding of the satellite footprints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004cosp...35..689K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004cosp...35..689K"><span>An investigation of ionospheric disturbances over the north-eastern region of Russia in October 2003 using <span class="hlt">auroral</span> images and data from a network of ground-based instruments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kurkin, V. I.; Afraimovich, E. L.; Berngardt, O. I.; Zherebtsov, G. A.; Litovkin, G. I.; Matyushonok, S. M.; Medvedev, A. V.; Potekhin, A. P.; Ratovsky, K. G.; Shpynev, B. G.</p> <p></p> <p>Presented are the results from analyzing the experimental data from the Irkutsk incoherent scatter (IS) radar, a network of magnetometers, GPS receivers, digital ionosounders for vertical- and oblique-incidence sounding combined with <span class="hlt">auroral</span> images during geomagnetic disturbances as a consequence of high flaring activity of the Sun from October 19 to 29, 2003. The position of the <span class="hlt">auroral</span> oval was determined using NOAA POES and DMSP satellite data available through the Internet. For substorms of October 21-22 and 24-25, significant (up to ˜ 50%) negative disturbances of <span class="hlt">electron</span> density were recorded during the nighttime and daytime in the longitude sector from 90E to 150E from subauroral to mid-latitudes (up to ˜ 50N). During the nighttime the equatorial boundary of the <span class="hlt">auroral</span> oval reached ˜ 55N (invariant latitude). The Irkutsk IS radar during that period recorded coherent echoes from ionospheric E-layer irregularities generated near the oval boundary. The strongest ionospheric disturbances throughout the aforementioned region were recorded on October 28 and 29 after two powerful flares of class X17.5 and X10.0 that occurred on October 28 and 29. A combined analysis of <span class="hlt">auroral</span> images and data from ground-based radiophysical facilities made it possible to study the dynamics of the boundaries of the <span class="hlt">auroral</span> oval and ionospheric trough during strong geomagnetic disturbances. A dramatic displacement of the <span class="hlt">auroral</span> oval boundary (up to ˜ 46N of invariant latitude) and a long-lasting generation of a broad spectrum of irregularities and wave-like disturbances in the ionosphere were recorded. During the daytime on October 30 and 31, negative disturbances were recorded over most of the region in the ionospheric F-layer reaching 60-70%, which were replaced the next day by positive disturbances with ˜ 30% amplitude. Negative disturbances of <span class="hlt">electron</span> density during the nighttime were accompanied by a substantial rise of <span class="hlt">electron</span> (by ˜ 1500K) and ion (by ˜ 1000K</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840040873&hterms=generation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgeneration%2BZ','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840040873&hterms=generation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgeneration%2BZ"><span>Generation of <span class="hlt">auroral</span> kilometric and Z mode radiation by the cyclotron maser mechanism</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Omidi, N.; Gurnett, D. A.; Wu, C. S.</p> <p>1984-01-01</p> <p>The relativistic Doppler-shifted cyclotron resonance condition for EM wave interactions with a plasma defines an ellipse in velocity space when the product of the index of refraction and cosine of the wave normal angle is less than or equal to unity, and defines a partial ellipse when the product is greater than unity. It is also noted that waves with frequencies greater than the gyrofrequency can only resonate with particles moving in the same direction along the magnetic field, while waves with lower frequencies than these resonate with particles moving in both directions along the magnetic field. It is found, in the case of <span class="hlt">auroral</span> kilometric radiation, that both the upgoing and the downgoing <span class="hlt">electrons</span> are unstable and can give rise to this radiation's growth. The magnitudes of the growth rates for both the upgoing and downgoing <span class="hlt">auroral</span> kilometric radiation are comparable, and indicate that the path lengths needed to account for the observed intensities of this radiation are of the order of a few hundred km, which is probably too large. Growth rate calculations for the Z mode radiation show that, for wave frequencies just below the gyrofrequency and wave normal angles at or near 90 deg, the <span class="hlt">electron</span> distribution is unstable and the growth rates are large enough to account for the observed intensities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790052142&hterms=History+Wave+Energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DHistory%2BWave%2BEnergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790052142&hterms=History+Wave+Energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DHistory%2BWave%2BEnergy"><span><span class="hlt">Auroral</span> origin of medium scale gravity waves in neutral composition and temperature</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chandra, S.; Spencer, N. W.; Krankowsky, D.; Laemmerzahl, P.</p> <p>1979-01-01</p> <p>The kinetic temperature and neutral composition data obtained from the Aeros B neutral atmosphere temperature experiment and the neutral and ion mass spectrometer show spatial structures characteristic of medium scale gravity waves with a wavelength in the range of several hundred kilometers. These waves are associated with <span class="hlt">auroral</span> activity, and their spatial structure reflects the time history of the <span class="hlt">auroral</span> electrojet. The medium scale gravity waves tend to propagate to mid-latitudes on the nightside. On the dayside their range is limited to high latitudes. Gravity waves are carriers of <span class="hlt">auroral</span> energy to middle and low latitudes where they may cause irreversible changes in temperature via viscous dissipation. Since <span class="hlt">auroral</span> activity occurs frequently, it is suggested that this energy reaches the mid-latitude region of the thermosphere much more frequently than is indicated by planetary magnetic indices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1524..267G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1524..267G"><span>Studies on effective atomic numbers for photon energy absorption and <span class="hlt">electron</span> density of some narcotic drugs in the energy range 1 <span class="hlt">keV</span>-20 MeV</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gounhalli, Shivraj G.; Shantappa, Anil; Hanagodimath, S. M.</p> <p>2013-04-01</p> <p>Effective atomic numbers for photon energy absorption ZPEA,eff, photon interaction ZPI,eff and for <span class="hlt">electron</span> density Nel, have been calculated by a direct method in the photon-energy region from 1 <span class="hlt">keV</span> to 20 MeV for narcotic drugs, such as Heroin (H), Cocaine (CO), Caffeine (CA), Tetrahydrocannabinol (THC), Cannabinol (CBD), Tetrahydrocannabivarin (THCV). The ZPEA,eff, ZPI,eff and Nel values have been found to change with energy and composition of the narcotic drugs. The energy dependence ZPEA,eff, ZPI,eff and Nel is shown graphically. The maximum difference between the values of ZPEA,eff, and ZPI,eff occurs at 30 <span class="hlt">keV</span> and the significant difference of 2 to 33% for the energy region 5-100 <span class="hlt">keV</span> for all drugs. The reason for these differences is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950059011&hterms=energy+baseline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Denergy%2Bbaseline','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950059011&hterms=energy+baseline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Denergy%2Bbaseline"><span>Effects of a parallel electric field and the geomagnetic field in the topside ionosphere on <span class="hlt">auroral</span> and photoelectron energy distributions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.</p> <p>1993-01-01</p> <p>The consequences of electric field acceleration and an inhomogeneous magnetic field on <span class="hlt">auroral</span> <span class="hlt">electron</span> energy distributions in the topside ionosphere are investigated. The one-dimensional, steady state <span class="hlt">electron</span> transport equation includes elastic and inelastic collisions, an inhomogeneous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of O(+) and H(+), and the <span class="hlt">electron</span> and ion energy equations to derive the <span class="hlt">electron</span> and ion temperatures. The system of coupled <span class="hlt">electron</span> transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the <span class="hlt">electron</span> distribution function is investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the <span class="hlt">electron</span> flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary <span class="hlt">electrons</span> and decelerates the upward directed component. Above about 400 km the inhomogeneous magnetic field produces anisotropies in the angular distribution of the <span class="hlt">electron</span> flux. The effects of the perturbed energy distributions on <span class="hlt">auroral</span> spectral emission features are noted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970014275&hterms=energy+baseline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Denergy%2Bbaseline','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970014275&hterms=energy+baseline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Denergy%2Bbaseline"><span>Effects of a Parallel Electric Field and the Geomagnetic Field in the Topside Ionosphere on <span class="hlt">Auroral</span> and Photoelectron Energy Distributions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.</p> <p>1993-01-01</p> <p>The consequences of electric field acceleration and an inhomogencous magnetic field on <span class="hlt">auroral</span> <span class="hlt">electron</span> energy distributions in the topside ionosphere are investigated. The one- dimensional, steady state <span class="hlt">electron</span> transport equation includes elastic and inelastic collisions, an inhomogencous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of 0(+) and H(+), and the <span class="hlt">electron</span> and ion energy equations to derive the <span class="hlt">electron</span> and ion temperatures. The system of coupled <span class="hlt">electron</span> transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the <span class="hlt">electron</span> distribution function in investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the <span class="hlt">electron</span> flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary <span class="hlt">electrons</span> and decelerates the upward directed component. Above about 400 km the inhomogencous magnetic field produces anisotropies in the angular distribution of the <span class="hlt">electron</span> flux. The effects of the perturbed energy distributions on <span class="hlt">auroral</span> spectral emission features are noted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26C....11..138L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26C....11..138L"><span>The <span class="hlt">Auroral</span> Planetary Imaging and Spectroscopy (APIS) service</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lamy, L.; Prangé, R.; Henry, F.; Le Sidaner, P.</p> <p>2015-06-01</p> <p>The <span class="hlt">Auroral</span> Planetary Imaging and Spectroscopy (APIS) service, accessible online, provides an open and interactive access to processed <span class="hlt">auroral</span> observations of the outer planets and their satellites. Such observations are of interest for a wide community at the interface between planetology, magnetospheric and heliospheric physics. APIS consists of (i) a high level database, built from planetary <span class="hlt">auroral</span> observations acquired by the Hubble Space Telescope (HST) since 1997 with its mostly used Far-Ultraviolet spectro-imagers, (ii) a dedicated search interface aimed at browsing efficiently this database through relevant conditional search criteria and (iii) the ability to interactively work with the data online through plotting tools developed by the Virtual Observatory (VO) community, such as Aladin and Specview. This service is VO compliant and can therefore also been queried by external search tools of the VO community. The diversity of available data and the capability to sort them out by relevant physical criteria shall in particular facilitate statistical studies, on long-term scales and/or multi-instrumental multi-spectral combined analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5751414-coherent-generation-auroral-kilometric-radiation-nonlinear-beatings-between-electrostatic-waves','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5751414-coherent-generation-auroral-kilometric-radiation-nonlinear-beatings-between-electrostatic-waves"><span>Coherent generation of the <span class="hlt">auroral</span> kilometric radiation by nonlinear beatings between electrostatic waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Pellat, R.; Roux, A.</p> <p>1979-09-01</p> <p>The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma is studied analytically. These waves, which are driven unstable by <span class="hlt">auroral</span> beams of <span class="hlt">electrons</span>, are shown to suffer a further geometrical amplification while they propagate toward cut-off. Simultaneously their group velocities tend to be aligned with the geomagnetic field. Then it is shown that the electrostatic energy tends to accumulate at or near ..omega../sub L/H and ..omega../sub U/H, the local lower and upper hybrid frequencies. Due to this process, large amplitude electrostatic waves with very narrow spectra should be observed near these frequencies at any place along themore » <span class="hlt">auroral</span> field lines where intense beam driven instability takes place. These intense quasi-monochromatic electrostatic waves are then shown to give rise by a coherent nonlinear three wave process to an intense electromagnetic radiation. Provided that the ratio ..omega../sub p/e/..omega../sub c/e tends to be smaller than unity, it is shown that the most intense radiation should be observed at 2..omega../sub U/H in the extraordinary mode.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E3538V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E3538V"><span>Radiation induced conductivity of polycarbonate doped with different concentrations of aromatic hydrazone DEH</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vladimir, Saenko; Novikov, Lev; Tyutnev, Andrey</p> <p></p> <p>Radiation induced conductivity (RIC) of polymers widely used on present-day spacecraft plays is an important factor affecting their charging by the hot plasma of the Earth’s magnetosphere. As a result, researchers pay special attention to laboratory investigations of RIC in polymers excited by 10 -100 <span class="hlt">keV</span> <span class="hlt">electrons</span> prevailing in the hot magnetospheric plasma, including <span class="hlt">auroral</span> radiation. Due to fluctuating fluxes of plasma <span class="hlt">electrons</span> and especially of <span class="hlt">auroral</span> <span class="hlt">electrons</span>, it is very important to know how RIC depends on time. In our report we present RIC results observed in polycarbonate (PC) molecularly doped with aromatic hydrazone DEH (10 to 30 mas. percent) under continuous irradiation with 50 <span class="hlt">keV</span> <span class="hlt">electrons</span>. It has been found that RIC behavior in this material differs markedly from what we observed earlier in most of the polymers. After beginning of the stepwise irradiation, the RIC of PC+DEH rises fast to the quasistationary level but unlike common polymers, does not fall by an order of magnitude, instead it starts to increase further thus causing the accumulating space charge to decrease. This fact combined with the confirmed high radiation and temperature tolerance allows us to recommend this material for application on the spacecraft outer surface and specifically, as a thermal blanket.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA51B2391S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA51B2391S"><span>Mid-latitude Plasma Irregularities During Sub-<span class="hlt">Auroral</span> Polarization Streams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, N.; Loper, R. D.</p> <p>2017-12-01</p> <p>Geomagnetic storming impacts the ionosphere in different ways at different latitudes. In the mid latitudes, Sub-<span class="hlt">Auroral</span> Polarization Streams (SAPS) may trigger a redistribution of plasma leading to the creation of ionospheric troughs, storm enhanced density plumes, and acceleration of sub-<span class="hlt">auroral</span> ion drifts. Solar cycle data, real time space weather satellite data, and radar data will be analyzed to study mid-latitude plasma densities and characterize the plasma anomalies SAPS create in order to increase short-term mid-latitude space weather forecasting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM53A..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM53A..04L"><span>Strong Ionospheric <span class="hlt">Electron</span> Heating Associated With Pulsating Auroras - A Swarm Survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, J.; Yang, B.; Burchill, J. K.; Donovan, E.; Knudsen, D. J.</p> <p>2016-12-01</p> <p>A pulsating aurora is a repetitive modulation of <span class="hlt">auroral</span> luminosity with periods typically of the order of 1-30 sec. It is often observed in the equatorward portion of the <span class="hlt">auroral</span> oval. While it is generally recognized that the ultimate source of the pulsating <span class="hlt">auroral</span> precipitation comes from energetic <span class="hlt">electrons</span> of magnetospheric origin, investigating the ionospheric signature of the pulsating aurora may offer clues to the magnetosphere-ionosphere coupling aspect of the pulsating aurora and, under certain circumstance, to the generation mechanism of the pulsating aurora. In this study, we perform an extensive survey on the ionospheric signatures (<span class="hlt">electron</span> temperature, plasma density and field-aligned current etc.) of pulsating auroras using Swarm satellite data. Via the survey we repeatedly identify a strong <span class="hlt">electron</span> temperature enhancement associated with the pulsating aurora. On average, the <span class="hlt">electron</span> temperature at Swarm satellite altitude ( 500 km) increases from 2100 K at subauroral altitudes to a peak of 2900 K upon entering the pulsating aurora patch. This indicates that the pulsating auroras may act as an important heating source of the nightside ionosphere/thermosphere. On the other hand, no well-defined trend of plasma density variation associated with pulsating auroras is identified in the survey. There often exist moderate upward field-aligned currents (up to a few mA/m2) within the pulsating <span class="hlt">auroral</span> patch when the patch is "on" during the traversal of satellites [Gillies et al., 2015], and the <span class="hlt">electron</span> temperature enhancement is found to be positively correlated with the magnitude of the field-aligned current. In a few events with high-resolution Swarm electric field instrument (EFI) data, we find that the on-time pulsating <span class="hlt">auroral</span> patch is associated with structured electric field disturbances with peaks exceeding 10 mV/m. Based upon observations and ionospheric models, we consider and evaluate several possible mechanisms that may account for the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM13F4230H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM13F4230H"><span>Ground and satellite observations of multiple sun-aligned <span class="hlt">auroral</span> arcs on the duskside</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hosokawa, K.; Maggiolo, R.; Zhang, Y.; Fear, R. C.; Fontaine, D.; Cumnock, J. A.; Kullen, A.; Milan, S. E.; Kozlovsky, A.; Echim, M.; Shiokawa, K.</p> <p>2014-12-01</p> <p>Sun-aligned <span class="hlt">auroral</span> arcs (SAAs) are one of the outstanding phenomena in the high-latitude region during periods of northward interplanetary magnetic field (IMF). Smaller scale SAAs tend to occur either in the duskside or dawnside of the polar cap and are known to drift in the dawn-dusk direction depending on the sign of the IMF By. Studies of SAAs are of particular importance because they represent dynamical characteristics of their source plasma in the magnetosphere, for example in the interaction region between the solar wind and magnetosphere or in the boundary between the plasma sheet and tail lobe. To date, however, very little has been known about the spatial structure and/or temporal evolution of the magnetospheric counterpart of SAAs. In order to gain more comprehensive understanding of the field-aligned plasma transport in the vicinity of SAAs, we have investigated an event of SAAs on November 10, 2005, during which multiple SAAs were detected by a ground-based all-sky camera at Resolute Bay, Canada. During this interval, several SAAs were detached from the duskside oval and moved poleward. The large-scale structure of these arcs was visualized by space-based imagers of TIMED/GUVI and DMSP/SSUSI. In addition to these optical observations, we employ the Cluster satellites to reveal the high-altitude particle signature corresponding to the small-scale SAAs. The ionospheric footprints of the 4 Cluster satellites encountered the SAAs sequentially and observed well correlated enhancements of <span class="hlt">electron</span> fluxes at weak energies (< 1 <span class="hlt">keV</span>). The Cluster satellites also detected signatures of upflowing beams of ions and <span class="hlt">electrons</span> in the vicinity of the SAAs. This implies that these ions and <span class="hlt">electrons</span> were accelerated upward by a quasi-stationary electric field existing in the vicinity of the SAAs and constitute a current system in the magnetosphere-ionosphere coupling system. Ionospheric convection measurement from one of the SuperDARN radars shows an indication that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM13D4196M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM13D4196M"><span>Relative Timing of Substorm-Associated Processes in the Near-Earth Magnetotail and Development of <span class="hlt">Auroral</span> Onset Arc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miyashita, Y.; Ieda, A.; Machida, S.; Hiraki, Y.; Angelopoulos, V.; McFadden, J. P.; Auster, H. U.; Mende, S. B.; Donovan, E.; Larson, D. E.</p> <p>2014-12-01</p> <p>We have studied the relative timing of the processes in the near-Earth magnetotail and development of <span class="hlt">auroral</span> onset arc at the beginning of the expansion phase, based on substorm events observed by the THEMIS spacecraft and ground-based all-sky imagers. The THEMIS all-sky imagers can observe auroras over a wide area with temporal and spacial resolutions higher than spacecraft-borne cameras. This enables us to investigate the timing of <span class="hlt">auroral</span> development in more detail than before. A few min after the appearance and intensification of an <span class="hlt">auroral</span> onset arc, it begins to form wave-like structure. Then <span class="hlt">auroral</span> poleward expansion begins another few min later. THEMIS magnetotail observations clearly show that magnetic reconnection is initiated at X~-20 Re at least 1-2 min before the intensification of <span class="hlt">auroral</span> onset arc. Then low-frequency waves are excited in the plasma sheet at X~-10 Re 2 min before dipolarization, which is simultaneous with the formation of <span class="hlt">auroral</span> wave-like structure. Dipolarization begins at the same time as the <span class="hlt">auroral</span> poleward expansion. These results suggest that near-Earth magnetic reconnection plays some role in the development of dipolarization and <span class="hlt">auroral</span> onset arc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM51E2597M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM51E2597M"><span>Development of the Near-Earth Magnetotail and the <span class="hlt">Auroral</span> Arc Associated with Substorm Onset: Evidence for a New Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miyashita, Y.; Hiraki, Y.; Angelopoulos, V.; Ieda, A.; Machida, S.</p> <p>2015-12-01</p> <p>We have studied the time sequence of the development of the near-Earth magnetotail and the <span class="hlt">auroral</span> arc associated with a substorm onset, using the data from the THEMIS spacecraft and ground-based observatories at high temporal and spatial resolutions. We discuss four steps of the <span class="hlt">auroral</span> development, linking them to magnetotail changes: the <span class="hlt">auroral</span> fading, the initial brightening of an <span class="hlt">auroral</span> onset arc, the enhancement of the wave-like structure, and the poleward expansion. A case study shows that near-Earth magnetic reconnection began at X~-17 RE at least ~3 min before the <span class="hlt">auroral</span> initial brightening and ~1 min before the <span class="hlt">auroral</span> fading. Ionospheric large-scale convection also became enhanced just before the <span class="hlt">auroral</span> fading and before the <span class="hlt">auroral</span> initial brightening. Then low-frequency waves were amplified in the plasma sheet at X~-10 RE, with the pressure increase due to the arrival of the earthward flow from the near-Earth reconnection site ~20 s before the enhancement of the <span class="hlt">auroral</span> wave-like structure. Finally, the dipolarization began ~30 s before the <span class="hlt">auroral</span> poleward expansion. On the basis of the present observations, we suggest that near-Earth magnetic reconnection plays two roles in the substorm triggering. First, it generates a fast earthward flow and Alfvén waves. When the Alfvén waves which propagate much faster than the fast flow reach the ionosphere, large-scale ionospheric convection is enhanced, leading to the <span class="hlt">auroral</span> initial brightening and subsequent gradual growth of the <span class="hlt">auroral</span> wave-like structure. Second, when the reconnection-initiated fast flow reaches the near-Earth magnetotail, it promotes rapid growth of an instability, such as the ballooning instability, and the <span class="hlt">auroral</span> wave-like structure is further enhanced. When the instability grows sufficiently, the dipolarization and the <span class="hlt">auroral</span> poleward expansion are initiated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM51D2522O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM51D2522O"><span>Field-aligned Currents Induced by Electrostatic Polarization at the Ionosphere: Application to the Poleward Boundary Intensification (PBI) of <span class="hlt">Auroral</span> Emission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ohtani, S.; Yoshikawa, A.</p> <p>2016-12-01</p> <p>Although the field-aligned currents (Birkeland currents) are generally considered to be driven by magnetospheric processes, it is possible that some field-aligned currents are locally induced in the ionosphere in the presence of sharp conductance gradient. In this presentation we shall discuss the poleward boundary intensification (PBI) of <span class="hlt">auroral</span> emission as an example effect of such electrostatic polarization. The observations show that the PBIs are very often preceded by the fast polar cap convection approaching the nightside <span class="hlt">auroral</span> oval. We propose that the ionospheric currents driven by the associated electric field diverges/converges at the poleward boundary of the <span class="hlt">auroral</span> oval as the background ionospheric conductance changes sharply in space, and they close with field-aligned currents. The associated upward field-aligned current is accompanied by <span class="hlt">electron</span> precipitation, which may cause <span class="hlt">auroral</span> emission as observed as PBIs. We test this idea by modeling the ionosphere as a slab-shaped enhancement of conductance and the polar cap flow channel as a pair of upward and downward FACs. The results show that (i) a pair of upward and downward FACs is induced at the poleward boundary when the front of the polar cap flow channel approaches the <span class="hlt">auroral</span> oval; (ii) the upward FAC extends westward much wider in longitude than the flow channel; (iii) the peak FAC density is significantly larger than the incident FAC; and (iv) the induced upward and downward FACs are distributed almost symmetrically in longitude, indicating that the Pedersen polarization dominates the Hall polarization. These results are consistent with some general characteristics of PBIs, which are rather difficult to explain if the PBIs are the ionospheric manefestation of distant reconnection as often suggested.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA263158','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA263158"><span><span class="hlt">Auroral</span>-E Observations: The First Year’s Data.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-02-01</p> <p>incidence-sound- ing (VIS) ionograms. One group, generally called <span class="hlt">auroral</span>-E, includes nighttime E (par- ticle E) of the k type and E of the r type (Esr...toward solar minimum. <span class="hlt">Auroral</span>-E tended to occur in clusters or "swarms" during periods of increased geo- magnetic activity. Figures 15a, 15b, and 15c show...midnight and several hours after local midnight. In the hours between 2200 and 0300 local time, when the K index is sufficiently high to place the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AdSpR..54.1786E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AdSpR..54.1786E"><span>Nonlinear <span class="hlt">electron</span>-acoustic rogue waves in <span class="hlt">electron</span>-beam plasma system with non-thermal hot <span class="hlt">electrons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.</p> <p>2014-11-01</p> <p>The properties of nonlinear <span class="hlt">electron</span>-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold <span class="hlt">electron</span> fluid, non-thermal hot <span class="hlt">electrons</span> obeying a non-thermal distribution, an <span class="hlt">electron</span> beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles on the <span class="hlt">electron</span> beam and energetic population parameter are discussed. The results of the present investigation may be applicable in <span class="hlt">auroral</span> zone plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910017323','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910017323"><span>Theoretical and experimental studies relevant to interpretation of <span class="hlt">auroral</span> emissions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Keffer, Charles E.</p> <p>1991-01-01</p> <p>The accomplishments achieved over the past year are detailed with emphasis on the interpretation or <span class="hlt">auroral</span> emissions and studies of potential spacecraft-induced contamination effects. Accordingly, the research was divided into two tasks. The first task is designed to add to the understanding of space vehicle induced external contamination. An experimental facility for simulation of the external environment for a spacecraft in low earth orbit was developed. The facility was used to make laboratory measurements of important phenomena required for improving the understanding of the space vehicle induced external environment and its effect on measurement of <span class="hlt">auroral</span> emissions from space-based platforms. A workshop was sponsored to provide a forum for presentation of the latest research by nationally recognized experts on space vehicle contamination and to discuss the impact of this research on future missions involving space-based platforms. The second task is to add an ab initio <span class="hlt">auroral</span> calculation to the extant ionospheric/thermospheric global modeling capabilities. Once the addition of the code was complete, the combined model was to be used to compare the relative intensities and behavior of various emission sources (dayglow, aurora, etc.). Such studies are essential to an understanding of the types of vacuum ultraviolet (VUV) <span class="hlt">auroral</span> images which are expected to be available within two years with the successful deployment of the Ultraviolet Imager (UVI) on the ISTP POLAR spacecraft. In anticipation of this, the second task includes support for meetings of the science working group for the UVI to discuss operational and data analysis needs. Taken together, the proposed tasks outline a course of study designed to make significant contributions to the field of space-based <span class="hlt">auroral</span> imaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22409711-we-bre-impact-iudr-rat-glioma-cell-survival-kev-photo-activated-auger-electron-therapy','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22409711-we-bre-impact-iudr-rat-glioma-cell-survival-kev-photo-activated-auger-electron-therapy"><span>WE-E-BRE-08: Impact of IUdR in Rat 9L Glioma Cell Survival for 25–35 <span class="hlt">KeV</span> Photo-Activated Auger <span class="hlt">Electron</span> Therapy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Alvarez, D; Hogstrom, K; Mary Bird Perkins Cancer Center, Baton Rouge, LA</p> <p>2014-06-15</p> <p>Purpose: To determine the biological effect from Auger <span class="hlt">electrons</span> with 9% and 18% iododeoxyuridine (IUdR) incorporated into the DNA of rat 9L glioma cells at photon energies above and below the K-edge of iodine (33.2 <span class="hlt">keV</span>). Methods: Rat 9L glioma cell survival versus dose curves with 0%, 9%, and 18% thymidine replacement with IUdR were measured using four irradiation energies (4 MV x-rays; monochromatic 35, 30, and 25 <span class="hlt">keV</span> synchrotron photons). For each of 11 conditions (Energy, %IUdR) survival curves were fit to the data (826 cell cultures) using the linear-quadratic model. The ratio of doses resulting in 10% survivalmore » gave sensitization enhancement ratios (SER10) from which contributions due to linear-energy transfer (LET), radiosensitization (RS), and Auger effect (AE) were extracted. Results: At 35, 30, and 25 <span class="hlt">keV</span>, SER10,LET values were 1.08±0.03, 1.22±0.02, and 1.37±0.02, respectively. At 4 MV SER10,RS values for 9% and 18% IUdR were 1.28±0.02 and 1.40±0.02, respectively. Assuming LET effects are independent of %IUdR and radiosensitization effects are independent of energy, SER10,AE values for 18% IUdR at 35, 30, and 25 <span class="hlt">keV</span> were 1.35±0.05, 1.06±0.03, and 0.98±0.03, respectively; values for 9% IUdR at 35 and 25 <span class="hlt">keV</span> were 1.01±0.04 and 0.82±0.02, respectively. Conclusion: For 18% IUdR the radiosensitization effect of 1.40 and the Auger effect of 1.35 at 35 <span class="hlt">keV</span> are equally important to the combined effect of 1.90. No measureable Auger effect was observed for energies below the K-edge at 20 and 25 <span class="hlt">keV</span>, as expected. The insignificant Auger effect at 9% IUdR was not expected. Additional data (40–70 <span class="hlt">keV</span>) and radiobiological modeling are being acquired to better understand the energy dependence of Auger <span class="hlt">electron</span> therapy with IUdR. Funding support in part by the National Science Foundation Graduate Research Fellowship Program and in part by Contract No. W81XWH-10-1-0005 awarded by the U.S. Army Research Acquisition Activity. This paper does not</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040000732&hterms=quasi+rest+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dquasi%2Brest%2Bpotential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040000732&hterms=quasi+rest+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dquasi%2Brest%2Bpotential"><span>Double Layers in Expanding Plasmas and Their Relevance to the <span class="hlt">Auroral</span> Plasma Processes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Singh, Nagendra; Khazanov, George</p> <p>2003-01-01</p> <p>When a dense plasma consisting of a cold and a sufficiently warm <span class="hlt">electron</span> population expands, a rarefaction shock forms [Bezzerides et al., 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm <span class="hlt">electron</span> population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [Barakat and Schunk, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the <span class="hlt">auroral</span> acceleration of <span class="hlt">electrons</span> and ions in the upward current region [Ergun et al., 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold <span class="hlt">electron</span> populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an ,extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold <span class="hlt">electrons</span> coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot <span class="hlt">electron</span> temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve <span class="hlt">electron</span>-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The <span class="hlt">electron-electron</span> two</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930047919&hterms=taylor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D60%26Ntt%3Dtaylor%2Bt%2Bb','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930047919&hterms=taylor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D60%26Ntt%3Dtaylor%2Bt%2Bb"><span>Artificial auroras in the upper atmosphere. I - <span class="hlt">Electron</span> beam injections</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Burch, J. L.; Mende, S. B.; Kawashima, N.; Roberts, W. T.; Taylor, W. W. L.; Neubert, T.; Gibson, W. C.; Marshall, J. A.; Swenson, G. R.</p> <p>1993-01-01</p> <p>The Atlas-1 Spacelab payload's Space Experiments with Particle Accelerators generated artificial <span class="hlt">electron</span> beams for the stimulation of <span class="hlt">auroral</span> emissions at southern <span class="hlt">auroral</span> latitudes. Optical measurements were made by the Shuttle Orbiter's onboard TV cameras, as well as by the Atmospheric Emissions Photometric Imager (in both white light and the 427.8 nm N2(+) emission line). Shuttle-based <span class="hlt">auroral</span> imaging furnished a novel perspective on the artificial auroras; the emissions were traced from 295 km to the 110 km level along the curved magnetic-field lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM53A..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM53A..03K"><span>An Overlooked Source of <span class="hlt">Auroral</span> Arc Field-Aligned Current</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knudsen, D. J.</p> <p>2017-12-01</p> <p>The search for the elusive generator of quiet <span class="hlt">auroral</span> arcs often focuses on magnetospheric pressure gradients, based on the static terms in the so-called Vaslyiunas equation [Vasyliunas, in "Magneospheric Currents", Geophysical Monograph 28, 1984]. However, magnetospheric pressure gradient scale sizes are much larger than the width of individual <span class="hlt">auroral</span> arcs. This discrepancy was noted by Atkinson [JGR, 27, p4746, 1970], who proposed that the <span class="hlt">auroral</span> arcs are fed instead by steady-state polarization currents, in which large-scale convection across quasi-static electric field structures leads to an apparent time dependence in the frame co-moving with the plasma, and therefore to the generation of ion polarization currents. This mechanism has been adopted by a series of authors over several decades, relating to studies of the ionospheric feedback instability, or IFI. However, the steady-state polarization current mechanism does not require the IFI, nor even the ionsophere. Specifically, any quasi-static electric field structure that is stationary relative to large-scale plasma convection is subject to the generation this current. This talk demonstrates that assumed convection speeds of the order of a 100 m/s across typical arc fields structures can lead to the generation FAC magintudes of several μA/m2, typical of values observed at the ionospheric footpoint of auoral arcs. This current can be viewed as originating within the M-I coupling medium, along the entire field line connecting an <span class="hlt">auroral</span> arc to its root in the magnetosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050210157','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050210157"><span>Eyewitness Reports of the Great <span class="hlt">Auroral</span> Storm of 1859</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Green, James L.; Boardsen, Scott; Odenwald, Sten; Humble, John; Pazamickas, Katherine A.</p> <p>2005-01-01</p> <p>The great geomagnetic storm of 1859 is really composed of two closely spaced massive worldwide <span class="hlt">auroral</span> events. The first event began on August 28th and the second began on September 2nd. It is the storm on September 2nd that results from the Carrington-Hodgson white light flare that occurred on the sun September l&. In addition to published scientific measurements; newspapers, ship logs and other records of that era provide an untapped wealth of first hand observations giving time and location along with reports of the <span class="hlt">auroral</span> forms and colors. At its height, the aurora was described as a blood or deep crimson red that was so bright that one "could read a newspaper by." Several important aspects of this great geomagnetic storm are simply phenomenal. <span class="hlt">Auroral</span> forms of all types and colors were observed to latitudes of 25deg and lower. A significant portion of the world's 125,000 miles of telegraph lines were also adversely affected. Many of - which were unusable for 8 hours or more and had a small but notable economic impact. T h s paper presents only a select few available first hand accounts of the Great <span class="hlt">Auroral</span> Event of 1859 in an attempt to give the modern reader a sense of how this spectacular display was received by the public from many places around the globe and present some other important historical aspects of the storm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950035957&hterms=quasi+particle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dquasi%2Bparticle','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950035957&hterms=quasi+particle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dquasi%2Bparticle"><span>Jupiter radio bursts and particle acceleration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Desch, Michael D.</p> <p>1994-01-01</p> <p>Particle acceleration processes are important in understanding many of the Jovian radio and plasma wave emissions. However, except for the high-energy <span class="hlt">electrons</span> that generate synchrotron emission following inward diffusion from the outer magnetosphere, acceleration processes in Jupiter's magnetosphere and between Jupiter and Io are poorly understood. We discuss very recent observations from the Ulysses spacecraft of two new Jovian radio and plamas wave emissions in which particle acceleration processes are important and have been addressed directly by complementary investigations. First, radio bursts known as quasi-periodic bursts have been observed in close association with a population of highly energetic <span class="hlt">electrons</span>. Second, a population of much lower energy (<span class="hlt">keV</span> range) <span class="hlt">electrons</span> on <span class="hlt">auroral</span> field lines can be shown to be responsible for the first observation of a Jovian plasma wave emission known as <span class="hlt">auroral</span> hiss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA43C..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA43C..01H"><span>Stormtime Simulations of Sub-<span class="hlt">Auroral</span> Polarization Streams (SAPS)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huba, J.; Sazykin, S. Y.; Coster, A. J.</p> <p>2017-12-01</p> <p>We present simulation results from the self-consistently coupled SAMI3/RCM code on the impact of geomagnetic storms on the ionosphere/plasmasphere system with an emphasis on the development of sub-<span class="hlt">auroral</span> plasma streams (SAPS). We consider the following storm events: March 31, 2001, March 17, 2013, March 17, 2015, September 3, 2012, and June 23, 2015. We compare and contrast the development of SAPS for these storms. The main results are the development of sub-<span class="hlt">auroral</span> (< 60 degrees) low-density, high-speed flows (1 - 2 km/s). Additionally, we discuss the impact on plasmaspheric dynamics. We compare our model results to data (e.g., Millstone Hill radar, GPS TEC).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......412M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......412M"><span>In situ analysis of measurements of <span class="hlt">auroral</span> dynamics and structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mella, Meghan R.</p> <p></p> <p>Two <span class="hlt">auroral</span> sounding rocket case studies, one in the dayside and one in the nightside, explore aspects of poleward boundary aurora. The nightside sounding rocket, Cascades-2 was launched on 20 March 2009 at 11:04:00 UT from the Poker Flat Research Range in Alaska, and flew across a series of poleward boundary intensifications (PBIs). Each of the crossings have fundamentally different in situ <span class="hlt">electron</span> energy and pitch angle structure, and different ground optics images of visible aurora. The different particle distributions show signatures of both a quasistatic acceleration mechanism and an Alfvenic acceleration mechanism, as well as combinations of both. The Cascades-2 experiment is the first sounding rocket observation of a PBI sequence, enabling a detailed investigation of the <span class="hlt">electron</span> signatures and optical aurora associated with various stages of a PBI sequence as it evolves from an Alfvenic to a more quasistatic structure. The dayside sounding rocket, Scifer-2 was launched on 18 January 2008 at 7:30 UT from the Andoya Rocket Range in Andenes, Norway. It flew northward through the cleft region during a Poleward Moving <span class="hlt">Auroral</span> Form (PMAF) event. Both the dayside and nightside flights observe dispersed, precipitating ions, each of a different nature. The dispersion signatures are dependent on, among other things, the MLT sector, altitude, source region, and precipitation mechanism. It is found that small changes in the shape of the dispersion have a large influence on whether the precipitation was localized or extended over a range of altitudes. It is also found that a single Maxwellian source will not replicate the data, but rather, a sum of Maxwellians of different temperature, similar to a Kappa distribution, most closely reproduces the data. The various particle signatures are used to argue that both events have similar magnetospheric drivers, that is, Bursty Bulk Flows in the magnetotail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....13474M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....13474M"><span>Itaca2 - Twin 76-ilat <span class="hlt">auroral</span> monitors.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Massetti, S.; Candidi, M.; Cerulli-Irelli, P.; Sparapani, R.; Maggiore, M.; Philipsen, H.; Baldetti, P.; Morbidini, A.</p> <p>2003-04-01</p> <p>In August 2002, the Italian Research Council (CNR) set up a new automatic <span class="hlt">auroral</span> monitor in Daneborg, on the North-East coast of Greenland, thanks to the support of the Progetto Nazionale Ricerche in Antartide (PNRA), and to the logistical support of the Danish Polar Center (DPC) and the Sirus-patrol (PNG). The new station is equipped with a digital all-sky camera, and it is intended to operate in conjunction with the other Italian station located in Ny-Ålesund, Svalbard: the two observatories constitute a system of twin <span class="hlt">auroral</span> monitors, owing almost the same invariant latitude of 76°, which is mainly devoted to the observation of the dayside red aurora connected to the cusp/LLBL magnetospheric region. When observing the high altitude dayside auroras, the field-of-views of the two stations are contiguous and allow the monitoring of the dayside <span class="hlt">auroral</span> activity over about 80° of magnetic longitude (about 5/6 hours MLT). Since many years ago, Svalbard Islands have been an ideal place for polar researches due to its scientific facilities, the easy access during all the year and the frequent flight connections. In Greenland, on the contrary, the set up and maintenance of a high-latitude station that has to operate during the winter season, needs more logistical efforts, and it would be impossible without the precious support of people residing in-situ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........27O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........27O"><span>Characterization and diagnostic methods for geomagnetic <span class="hlt">auroral</span> infrasound waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oldham, Justin J.</p> <p></p> <p>Infrasonic perturbations resulting from <span class="hlt">auroral</span> activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of <span class="hlt">auroral</span> infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic <span class="hlt">auroral</span> infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60 0 longitude east of the anti-Sun-Earth line and at ~770 North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active <span class="hlt">Auroral</span> Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic <span class="hlt">auroral</span> electrojet currents as primary sources of much of the observed infrasound, with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JGRA..10912213S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JGRA..10912213S"><span>Two types of energy-dispersed ion structures at the plasma sheet boundary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauvaud, J.-A.; Kovrazhkin, R. A.</p> <p>2004-12-01</p> <p>We study two main types of ion energy dispersions observed in the energy range ˜1 to 14 <span class="hlt">keV</span> on board the Interball-<span class="hlt">Auroral</span> (IA) satellite at altitudes 2-3 RE at the poleward boundary of the plasma sheet. The first type of structure is named velocity dispersed ion structures (VDIS). It is known that VDIS represent a global proton structure with a latitudinal width of ˜0.7-2.5°, where the ion overall energy increases with latitude. IA data allow to show that VDIS are made of substructures lasting for ˜1-3 min. Inside each substructure, high-energy protons arrive first, regardless of the direction of the plasma sheet boundary crossing. A near-continuous rise of the maximal and minimal energies of consecutive substructures with invariant latitude characterizes VDIS. The second type of dispersed structure is named time-of-flight dispersed ion structures (TDIS). TDIS are recurrent sporadic structures in H+ (and also O+) with a quasi-period of ˜3 min and a duration of ˜1-3 min. The maximal energy of TDIS is rather constant and reaches ≥14 <span class="hlt">keV</span>. During both poleward and equatorward crossings of the plasma sheet boundary, inside each TDIS, high-energy ions arrive first. These structures are accompanied by large fluxes of upflowing H+ and O+ ions with maximal energies up to 5-10 <span class="hlt">keV</span>. In association with TDIS, bouncing H+ clusters are observed in quasi-dipolar magnetic field tubes, i.e., equatorward from TDIS. The <span class="hlt">electron</span> populations generally have different properties during observations of VDIS and TDIS. The <span class="hlt">electron</span> flux accompanying VDIS first increases smoothly and then decreases after Interball-<span class="hlt">Auroral</span> has passed through the proton structure. The average <span class="hlt">electron</span> energy in the range ˜0.5-2 <span class="hlt">keV</span> is typical for <span class="hlt">electrons</span> from the plasma sheet boundary layer (PSBL). The <span class="hlt">electron</span> fluxes associated with TDIS increases suddenly at the polar boundary of the <span class="hlt">auroral</span> zone. Their average energy, reaching ˜5-8 <span class="hlt">keV</span>, is typical for CPS. A statistical analysis shows that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28880294','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28880294"><span>Discrete and broadband <span class="hlt">electron</span> acceleration in Jupiter's powerful aurora.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mauk, B H; Haggerty, D K; Paranicas, C; Clark, G; Kollmann, P; Rymer, A M; Bolton, S J; Levin, S M; Adriani, A; Allegrini, F; Bagenal, F; Bonfond, B; Connerney, J E P; Gladstone, G R; Kurth, W S; McComas, D J; Valek, P</p> <p>2017-09-06</p> <p>The most intense <span class="hlt">auroral</span> emissions from Earth's polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of <span class="hlt">electrons</span> by slowly evolving, powerful electric fields directed along the magnetic field lines that connect Earth's space environment to its polar regions. In contrast, Earth's less intense auroras are generally caused by wave scattering of magnetically trapped populations of hot <span class="hlt">electrons</span> (in the case of diffuse aurora) or by the turbulent or stochastic downward acceleration of <span class="hlt">electrons</span> along magnetic field lines by waves during transitory periods (in the case of broadband or Alfvénic aurora). Jupiter's relatively steady main aurora has a power density that is so much larger than Earth's that it has been taken for granted that it must be generated primarily by the discrete <span class="hlt">auroral</span> process. However, preliminary in situ measurements of Jupiter's <span class="hlt">auroral</span> regions yielded no evidence of such a process. Here we report observations of distinct, high-energy, downward, discrete <span class="hlt">electron</span> acceleration in Jupiter's <span class="hlt">auroral</span> polar regions. We also infer upward magnetic-field-aligned electric potentials of up to 400 kiloelectronvolts, an order of magnitude larger than the largest potentials observed at Earth. Despite the magnitude of these upward electric potentials and the expectations from observations at Earth, the downward energy flux from discrete acceleration is less at Jupiter than that caused by broadband or stochastic processes, with broadband and stochastic characteristics that are substantially different from those at Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPSC...10..830L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPSC...10..830L"><span>Updated modeling of Io and non-Io Radio <span class="hlt">Auroral</span> Emissions of Jupiter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Louis, C.; Lamy, L.; Zarka, P.; Cecconi, B.; Hess, S.</p> <p>2015-10-01</p> <p>The radio <span class="hlt">auroral</span> emissions produced by the Jupiter's magnetosphere between a few kHz and 40MHz, the most intense of our Solar System, are known since half a century, but they still drive many questions, and their deepened study is one of the main aim of the JUNO missions (arrival in July 2016). Jovian <span class="hlt">auroral</span> radio emissions are thought to be produced through the Cyclotron Maser Instability (CMI), from non-maxwellian weakly relativistic <span class="hlt">electrons</span> gyrating along high-latitude magnetic fields lines (Zarka, 1998). These emissions divide in different spectral components, driven or not by the moon Io. The origin and the relationship between kilometric, hectometric and decametric non-Io emissions in particular remains poorly understood. To investigate these emissions, we simulated numerical dynamic spectra with the most recent version of the ExPRES code - Exoplanetary and Planetary Radio Emission Simulator, available at http://maser.obspm.fr - already used to successfully model Io decametric and Saturn's kilometric arcshaped emissions (Hess et al., 2008, Lamy et al., 2008) and predict exoplanetary radio emissions (Hess et al., 2011). Such simulations bring direct constraints on the locus of active magnetic field lines and on the nature of CMI-unstable <span class="hlt">electrons</span> (Hess et al., submitted). We validated the new theoretical calculation of the beaming angle used by ExPRES, which now includes refraction at the source. We then built updated simulations of Io and non-Io emissions which were compared to the radio observations acquired by the Cassini spacecraft (Jupiter flyby in 2000) and the Nançay decameter array (routines observations of Jupiter).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982PhDT.........5Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982PhDT.........5Y"><span>Parallel Electric Field on <span class="hlt">Auroral</span> Magnetic Field Lines.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yeh, Huey-Ching Betty</p> <p>1982-03-01</p> <p>The interaction of Birkeland (magnetic-field-aligned) current carriers and the Earth's magnetic field results in electrostatic potential drops along magnetic field lines. The statistical distributions of the field-aligned potential difference (phi)(,(PARLL)) were determined from the energy spectra of <span class="hlt">electron</span> inverted "V" events observed at ionospheric altitude for different conditions of geomagnetic activity as indicated by the AE index. Data of 1270 <span class="hlt">electron</span> inverted "V"'s were obtained from Low-Energy <span class="hlt">Electron</span> measurements of the Atmosphere Explorer-C and -D Satellite (despun mode) in the interval January 1974-April 1976. In general, (phi)(,(PARLL)) is largest in the dusk to pre-midnight sector, smaller in the post-midnight to dawn sector, and smallest in the near noon sector during quiet and disturbed geomagnetic conditions; there is a steady dusk-dawn-noon asymmetry of the global (phi)(,(PARLL)) distribution. As the geomagnetic activity level increases, the (phi)(,(PARLL)) pattern expands to lower invariant latitudes, and the magnitude of (phi)(,(PARLL)) in the 13-24 magnetic local time sector increases significantly. The spatial structure and intensity variation of the global (phi)(,(PARLL)) distribution are statistically more variable, and the magnitudes of (phi)(,(PARLL)) have smaller correlation with the AE-index, in the post-midnight to dawn sector. A strong correlation is found to exist between upward Birkeland current systems and global parallel potential drops, and between <span class="hlt">auroral</span> <span class="hlt">electron</span> precipitation patterns and parallel potential drops, regarding their mophology, their intensity and their dependence of geomagnetic activity. An analysis of the fine-scale simultaneous current-voltage relationship for upward Birkeland currents in Region 1 shows that typical field-aligned potential drops are consistent with model predictions based on linear acceleration of the charge carriers through an electrostatic potential drop along convergent magnetic field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRA..123..364B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRA..123..364B"><span>Evidence for <span class="hlt">Auroral</span> Emissions From Callisto's Footprint in HST UV Images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bhattacharyya, Dolon; Clarke, John T.; Montgomery, Jordan; Bonfond, Bertrand; Gérard, Jean-Claude; Grodent, Denis</p> <p>2018-01-01</p> <p><span class="hlt">Auroral</span> emissions are expected from the footprint of Callisto in Jupiter's upper atmosphere owing to the known interaction of its atmosphere with Jupiter's magnetosphere, and from the observed <span class="hlt">auroral</span> emissions from the footprints of the other three Galilean satellites. The mapping of Callisto along modeled magnetic field lines at Jupiter, however, places the expected footprint at the same latitude as the main <span class="hlt">auroral</span> emissions, making it difficult to detect. We analyzed ultraviolet images of Jupiter taken using the Hubble Space Telescope/Advanced Camera for Surveys instrument during a large observing campaign in 2007. Using a coaddition method similar to one used for Enceladus, we have identified a strong candidate for the footprint of Callisto on 24 May 2007. We tested this finding by applying the same coaddition technique to a nearly identical <span class="hlt">auroral</span> configuration on 30 May 2007 when Callisto was behind Jupiter, not visible from Earth (central meridian longitude = 22°; sub-Callisto system III longitude = 327°). By comparing the two coadded images, we can clearly see the presence of a strongly subcorotating spot close to the expected Callisto footprint location on 24 May and its absence on 30 May. On 24 May Callisto was located in the current sheet. We also found a probable candidate on 26 May 2007 during which time Callisto was positioned below the current sheet. The measured location and intensity of the <span class="hlt">auroral</span> emission provide important information about the interaction of Callisto with Jupiter's magnetic field, the corotating plasma, and the neutral and ionized state of the thin atmosphere of Callisto.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AIPC..771...91B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..771...91B"><span><span class="hlt">Electron</span> Collisions in our Atmosphere — How the Microscopic Drives the Macroscopic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buckman, S. J.; Brunger, M. J.; Campbell, L.; Jelisavcic, M.; Petrovic, Z. Lj.</p> <p>2005-05-01</p> <p>Recent measurements of low energy, absolute <span class="hlt">electron</span> scattering cross sections for vibrational excitation of NO have been used to update the cross set used for modeling atmospheric <span class="hlt">auroral</span> processes. These new cross sections, which highlight the role that intermediate negative ions (resonances) play at energies below 5 eV in mediating vibrational excitation, also indicate that <span class="hlt">electron</span>-driven processes play an important role in the infrared (˜5 um) <span class="hlt">auroral</span> emissions from the NO molecule.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Icar..300..305S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Icar..300..305S"><span>Jupiter's <span class="hlt">auroral</span>-related stratospheric heating and chemistry II: Analysis of IRTF-TEXES spectra measured in December 2014</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Moses, J. I.; Hue, V.; Irwin, P. G. J.</p> <p>2018-01-01</p> <p>We present a retrieval analysis of TEXES (Texas Echelon Cross Echelle Spectrograph (Lacy et al., 2002)) spectra of Jupiter's high latitudes obtained on NASA's Infrared Telescope Facility on December 10 and 11th 2014. The vertical temperature profile and vertical profiles of C2H2, C2H4 and C2H6 were retrieved at both high-northern and high-southern latitudes and results were compared in 'quiescent' regions and regions known to be affected by Jupiter's aurora in order to highlight how <span class="hlt">auroral</span> processes modify the thermal structure and hydrocarbon chemistry of the stratosphere. In qualitative agreement with Sinclair et al. (2017a), we find temperatures in <span class="hlt">auroral</span> regions to be elevated with respect to quiescent regions at two discrete pressures levels at approximately 1 mbar and 0.01 mbar. For example, in comparing retrieved temperatures at 70°N, 60°W (a representative quiescent region) and 70°N, 180°W (centred on the northern <span class="hlt">auroral</span> oval), temperatures increase by 19.0 ± 4.2 K at 0.98 mbar, 20.8 ± 3.9 K at 0.01 mbar but only by 8.3 ± 4.9 K at the intermediate level of 0.1 mbar. We conclude that elevated temperatures at 0.01 mbar result from heating by joule resistance of the atmosphere and the energy imparted by <span class="hlt">electron</span> and ion precipitation. However, temperatures at 1 mbar are considered to result either from heating by shortwave radiation of <span class="hlt">aurorally</span>-produced haze particulates or precipitation of higher energy population of charged particles. Our former conclusion would be consistent with results of <span class="hlt">auroral</span>-chemistry models, that predict the highest number densities of <span class="hlt">aurorally</span>-produced haze particles at this pressure level (Wong et al., 2000, 2003). C2H2 and C2H4 exhibit enrichments but C2H6 remains constant within uncertainty when comparing retrieved concentrations in the northern <span class="hlt">auroral</span> region with quiescent longitudes in the same latitude band. At 1 mbar, C2H2 increases from 278.4 ± 40.3 ppbv at 70°N, 60°W to 564.4 ± 72.0 ppbv at 70°N, 180</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030067837&hterms=project+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dproject%2Bwaves','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030067837&hterms=project+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dproject%2Bwaves"><span>Wave and Particle Interactions in the High and Low-Altitude <span class="hlt">Auroral</span> Region During Rising Solar Activity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gurnett, Donald A.; Menietti, J. D.</p> <p>2003-01-01</p> <p>The project has resulted in four separate investigations, which are each in various stages of publication in the refereed scientific journals. The first investigation was of the generation of electrostatic <span class="hlt">electron</span> cyclotron waves observed by the Polar spacecraft throughout the <span class="hlt">auroral</span> regions, dayside cusp, and polar magnetosphere. We have since discovered that these waves are also present within the magnetopause and magnetosheath, which is one of the topics of a second study, entitled: 'Polar observations of plasma waves in and near the dayside magnetopause/magnetosheath.' A third study of plasma waves focussed on kilometric continuum (KC) emission. This work is reported in a paper entitled 'Near-source and Remote Observations of Kilometric Continuum Radiation From Multi-spacecraft Observations'.The final investigation of this program concerns the possible transverse heating of <span class="hlt">auroral</span> ions by impulsive wave structures. We summarize that substantial transverse ion heating has already occurred at lower altitudes. Abstracts of the above four studies are included in the Appendix to this final report.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850016292&hterms=F4&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DF4','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850016292&hterms=F4&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DF4"><span>Field-aligned currents observed in the vicinity of a moving <span class="hlt">auroral</span> arc</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goertz, C. K.; Bruening, K.</p> <p>1984-01-01</p> <p>The sounding rocket Porcupine F4 was launched into an <span class="hlt">auroral</span> arc and the field aligned currents were independently deduced from magnetic field measurements; the horizontal current deduced from the electric field measurements and height integrated conductivity calculations; and measurements of <span class="hlt">electron</span> fluxes. Above the arc the different methods agree. The magnetosphere acts as generator and the ionosphere as load. North of the arc, the first two methods disagree, possibly due to an Alfven wave carrying the observed magnetic field perturbation. The energy flow is out of the ionosphere. Here the ionosphere acts as generator and the magnetosphere as load.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730009663','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730009663"><span>Vertical distribution of vibrational energy of molecular nitrogen in a stable <span class="hlt">auroral</span> red arc and its effect on ionospheric <span class="hlt">electron</span> densities. Ph.D. Thesis - Catholic Univ. of Am.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Newton, G. P.</p> <p>1973-01-01</p> <p>Previous solutions of the problem of the distribution of vibrationally excited molecular nitrogen in the thermosphere have either assumed a Boltzmann distribution and considered diffusion as one of the loss processes or solved for the energy level populations and neglected diffusion. Both of the previous approaches are combined by solving the time dependent continuity equations, including the diffusion process, for the first six energy levels of molecular nitrogen for conditions in the thermosphere corresponding to a stable <span class="hlt">auroral</span> red arc. The primary source of molecular nitrogen excitation was subexcitation, and inelastic collisions between thermal <span class="hlt">electrons</span> and molecular nitrogen. The reaction rates for this process were calculated from published cross section calculations. The loss processes for vibrational energy were <span class="hlt">electron</span> and atomic oxygen quenching and vibrational energy exchange. The coupled sets of nonlinear, partial differential equations were solved numerically by employing finite difference equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM23A2216H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM23A2216H"><span>Time development of high-altitude <span class="hlt">auroral</span> acceleration region plasma, potentials, and field-aligned current systems observed by Cluster during a substorm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hull, A. J.; Chaston, C. C.; Fillingim, M. O.; Mozer, F.; Frey, H. U.</p> <p>2013-12-01</p> <p>The <span class="hlt">auroral</span> acceleration region is an integral link in the chain of events that transpire during substorms, and the currents, plasma and electric fields undergo significant changes driven by complex dynamical processes deep in the magnetotail. These <span class="hlt">auroral</span> acceleration processes in turn accelerate and heat the plasma that ultimately leads to some of the most intense global substorm <span class="hlt">auroral</span> displays. The complex interplay between field-aligned current system formation, the development of parallel electric fields, and resultant changes in the plasma constituents that occur during substorms within or just above the <span class="hlt">auroral</span> acceleration zone remain unclear. We present Cluster multi-point observations within the high-altitude acceleration region (> 3 Re altitude) at key instances during the development of a substorm. Of particular emphasis is on the time-development of the plasma, potentials and currents that occur therein with the aim of ascertaining high-altitude drivers of substorm active <span class="hlt">auroral</span> acceleration processes and <span class="hlt">auroral</span> emission consequences. Preliminary results show that the initial onset is dominated by Alfvenic activity as evidenced by the sudden occurrence of relatively intense, short-spatial scale Alfvenic currents and attendant energy dispersed, counterstreaming <span class="hlt">electrons</span> poleward of the growth-phase arc. The Alfvenic currents are locally planar structures with characteristic thicknesses on the order of a few tens of kilometers. In subsequent passages by the other spacecraft, the plasma sheet region became hotter and thicker via the injection of new hot, dense plasma of magnetospheric origins poleward of the pre-existing growth phase arc. In association with the heating and/or thickening of the plasma sheet, the currents appeared to broaden to larger scales as Alfven dominated activity gave way to either inverted-V dominated or mixed inverted-V and Alfvenic behavior depending on location. The transition from Alfven dominated to inverted-V dominated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996A%26A...305..669L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996A%26A...305..669L"><span>A coherent nonlinear theory of <span class="hlt">auroral</span> Langmuir-Alfven-whistler (LAW) events in the planetary magnetosphere.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lopes, S. R.; Chian, A. C.-L.</p> <p>1996-01-01</p> <p>A coherent nonlinear theory of three-wave coupling involving Langmuir, Alfven and whistler waves is formulated and applied to the observation of <span class="hlt">auroral</span> LAW events in the planetary magnetosphere. The effects of pump depletion, dissipation and frequency mismatch in the nonlinear wave dynamics are analyzed. The relevance of this theory for understanding the fine structures of <span class="hlt">auroral</span> whistler-mode emissions and amplitude modulations of <span class="hlt">auroral</span> Langmuir waves is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PASJ...69...86H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PASJ...69...86H"><span>Records of <span class="hlt">auroral</span> candidates and sunspots in Rikkokushi, chronicles of ancient Japan from early 7th century to 887</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hayakawa, Hisashi; Iwahashi, Kiyomi; Tamazawa, Harufumi; Ebihara, Yusuke; Kawamura, Akito Davis; Isobe, Hiroaki; Namiki, Katsuko; Shibata, Kazunari</p> <p>2017-12-01</p> <p>We present the results of the surveys on sunspots and <span class="hlt">auroral</span> candidates in Rikkokushi, Japanese official histories from the early 7th century to 887, to review the solar and <span class="hlt">auroral</span> activities. In total, we found one sunspot record and 13 <span class="hlt">auroral</span> candidates in Rikkokushi. We then examine the records of the sunspots and <span class="hlt">auroral</span> candidates, compare the <span class="hlt">auroral</span> candidates with the lunar phase to estimate their reliability, and compare the records of the sunspots and <span class="hlt">auroral</span> candidates with the contemporary total solar irradiance reconstructed from radioisotope data. We also identify the locations of the observational sites to review possible equatorward expansion of the <span class="hlt">auroral</span> oval. These discussions suggest a major gap in <span class="hlt">auroral</span> candidates from the late 7th to early 9th centuries, which includes the candidate of the grand minimum reconstructed from the radioisotope data, a similar tendency as the distributions of sunspot records in contemporary China, and a relatively high magnetic latitude of observational sites with a higher potential for observing aurorae more frequently than at present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA111266','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA111266"><span>Anomalous Resistivity of <span class="hlt">Auroral</span> Field Lines.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1982-01-25</p> <p>Anomalous Resistivity on <span class="hlt">Auroral</span> Field Lines H-. L. R0VNLAND AND K. PAPADOPOULOS Laboratory for Plasma and Fusion Energy Studies$ University of Maryland...d in Stock 20, It difitir.oI from Reprt) It.SUPPLEMENTARY NOTES * Laboratory for Plasma and Fusion Energy Studies, University of NMarland, College</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982JGR....87.3591R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982JGR....87.3591R"><span><span class="hlt">Auroral</span> nitric oxide concentration and infrared emission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reidy, W. P.; Degges, T. C.; Hurd, A. G.; Stair, A. T., Jr.; Ulwick, J. C.</p> <p>1982-05-01</p> <p>Rocket-borne measurements of infrared <span class="hlt">auroral</span> emission by nitric oxide are analyzed. Four rocket flights provided opportunities to measure 5.3- and 2.7-micron NO emission by means of infrared fixed band radiometers and CVF spectrometers, narrow band photometers, and incident energy spectra on various occasions. Analysis of infrared emission profiles and <span class="hlt">electron</span> flux data indicates the NO density to be significantly enhanced with respect to midlatitude values. NO emission in the fundamental 5.3-micron band is attributed to resonance excitation by warm earth radiation, collisional excitation primarily by O atoms and chemiluminescence from the reaction of N with O2; with an energy efficiency of 0.015. The overtone band emission at 2.7 microns is accounted for by chemiluminescence produced with an energy efficiency of 0.0054. Total photon yield for the chemiluminescence reaction is estimated to range from 1.2 to 2.4 vibrational quanta per NO molecule.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA41C..06K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA41C..06K"><span>Statistical characterization of the Sub-<span class="hlt">Auroral</span> Polarization Stream (SAPS)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kunduri, B.; Baker, J. B.; Ruohoniemi, J. M.; Erickson, P. J.; Coster, A. J.; Oksavik, K.</p> <p>2017-12-01</p> <p>The Sub-<span class="hlt">Auroral</span> Polarization Stream (SAPS) is a narrow region of westward directed plasma convection typically observed in the dusk-midnight sector equatorward of the main <span class="hlt">auroral</span> oval. SAPS plays an important role in mid-latitude space weather dynamics and has a controlling influence on the evolution of large-scale plasma features, such as Storm Enhanced Density (SED) plumes. In this study, data from North American mid-latitude SuperDARN radars collected between January 2011 and December 2014 have been used to compile a database of SAPS events for statistical analysis. We examine the dependence of SAPS velocity magnitude and direction on geomagnetic activity and magnetic local time. The lowest speed limit and electric fields observed during SAPS are discussed and histograms of SAPS velocities for different Dst bins and MLAT-MLT locations are presented. We find significant differences in SAPS characteristics between periods of low and high geomagnetic activity, suggesting that SAPS are driven by different mechanisms during storm and non-storm conditions. To further explore this possibility, we have characterized the SAPS location and peak speed relative to the ionospheric trough specified by GPS Total <span class="hlt">Electron</span> Content (TEC) data from the MIT Haystack Madrigal database. A particular emphasis is placed on identifying the extent to which the location, structure, and depth of the trough may play a controlling influence on SAPS speeds during storm and non-storm periods. The results are interpreted in terms of the current paradigm for active thermosphere-ionosphere feedback being an important component of SAPS physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011745','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011745"><span>V and V Efforts of <span class="hlt">Auroral</span> Precipitation Models: Preliminary Results</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zheng, Yihua; Kuznetsova, Masha; Rastaetter, Lutz; Hesse, Michael</p> <p>2011-01-01</p> <p><span class="hlt">Auroral</span> precipitation models have been valuable both in terms of space weather applications and space science research. Yet very limited testing has been performed regarding model performance. A variety of <span class="hlt">auroral</span> models are available, including empirical models that are parameterized by geomagnetic indices or upstream solar wind conditions, now casting models that are based on satellite observations, or those derived from physics-based, coupled global models. In this presentation, we will show our preliminary results regarding V&V efforts of some of the models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSA33A2177F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSA33A2177F"><span>Preliminary Observations of Ionospheric Response to an <span class="hlt">Auroral</span> Driver from the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) Sounding Rocket Campaign</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernandes, P. A.; Lynch, K. A.; Hysell, D. L.; Powell, S.; Miceli, R.; Hampton, D. L.; Ahrns, J.; Lessard, M.; Cohen, I. J.; Moen, J. I.; Bekkeng, T.</p> <p>2012-12-01</p> <p>The nightside sounding rocket MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) launched from Poker Flat, AK, on February 19, 2012, and reached an apogee of 325km. MICA was launched into several discrete, localized arcs in the wake of a westward traveling surge. The MICA instrumentation included both in situ and ground based instruments, and was designed to measure the response of the ionosphere to an <span class="hlt">auroral</span> driver. More specifically, the science goal was to measure response of the ionosphere to a feedback instability in the ionospheric Alfvén resonator. The MICA payload included in situ particle, electric and magnetic field, and GPS instruments. The ground-based array consisted of a multitude of imagers, coherent and incoherent scatter radars, and a Fabry-Perot interferometer. We present observational characteristics of the response of the ionospheric plasma to the <span class="hlt">auroral</span> drivers inferred from inverting camera data. We compare the measured precipitating <span class="hlt">electron</span> population to inversions of camera images, which use a transport model to infer a 2D map of the precipitation. Comparisons show that as the payload passes through what appears to be an Alfvénic <span class="hlt">auroral</span> arc, the in situ <span class="hlt">electron</span> instrument shows dispersions indicative of Alfvénic activity. We then introduce measurements of the thermal ion distribution, to examine how the <span class="hlt">auroral</span> arcs drive a response in the ionosphere. The thermal ion data show that the payload potential strengthens as the payload passes through the arc. When including <span class="hlt">electron</span> density, temperature, and electric field data, we observe times in which the ionospheric environment changes as the precipitation changes, and times during which there is no measured response by the ionosphere. Future work will compare how the ion bulk flow as measured by the thermal ion instrument compares to the ExB drift as measured by the electric field instrument and to the neutral wind measurements from the Fabry-Perot interferometer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800018485','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800018485"><span>Trigger, an active release experiment that stimulated <span class="hlt">auroral</span> particle precipitation and wave emissions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Holmgren, G.; Bostroem, R.; Kelley, M. C.; Kintner, P. M.; Lundin, R.; Fahleson, U. V.; Bering, E. A.; Sheldon, W. R.</p> <p>1979-01-01</p> <p>The experiment design, including a description of the diagnostic and chemical release payload, and the general results are given for an <span class="hlt">auroral</span> process simulation experiment. A drastic increase of the field aligned charged particle flux was observed over the approximate energy range 10 eV to more than 300 <span class="hlt">keV</span>, starting about 150 ms after the release and lasting about one second. The is evidence of a second particle burst, starting one second after the release and lasting for tens of seconds, and evidence for a periodic train of particle bursts occurring with a 7.7 second period from 40 to 130 seconds after the release. A transient electric field pulse of 200 mv/m appeared just before the particle flux increase started. Electrostatic wave emissions around 2 kHz, as well as a delayed perturbation of the E-region below the plasma cloud were also observed. Some of the particle observations are interpreted in terms of field aligned electrostatic acceleration a few hundred kilometers above the injected plasma cloud. It is suggested that the acceleration electric field was created by an instability driven by field aligned currents originating in the plasma cloud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GMS...216..121M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GMS...216..121M"><span>Relationship between Alfvén Wave and Quasi-Static Acceleration in Earth's <span class="hlt">Auroral</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mottez, Fabrice</p> <p>2016-02-01</p> <p>There are two main categories of acceleration processes in the Earth's <span class="hlt">auroral</span> zone: those based on quasi-static structures, and those based on Alfvén wave (AW). AWs play a nonnegligible role in the global energy budget of the plasma surrounding the Earth because they participate in <span class="hlt">auroral</span> acceleration, and because <span class="hlt">auroral</span> acceleration conveys a large portion of the energy flux across the magnetosphere. Acceleration events by double layers (DLs) and by AW have mostly been investigated separately, but many studies cited in this chapter show that they are not independent: these processes can occur simultaneously, and one process can be the cause of the other. The quasi-simultaneous occurrences of acceleration by AW and by quasi-static structures have been observed predominantly at the polar cap boundary of <span class="hlt">auroral</span> arc systems, where often new bright arcs develop or intensify.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720023744','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720023744"><span>Magnetospheric <span class="hlt">electrons</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coroniti, F. V.; Thorne, R. M.</p> <p>1972-01-01</p> <p>Coupling of source, transport, and sink processes produces a fairly accurate model for the macroscopic structure and dynamics of magnetospheric <span class="hlt">electrons</span>. <span class="hlt">Auroral</span> <span class="hlt">electrons</span> are controlled by convective transport from a plasma sheet source coupled with a precipitation loss due to whistler and electrostatic plasma turbulence. Outer and inner zone <span class="hlt">electrons</span> are governed by radial diffusion transport from convection and acceleration sources external to the plasmapause and by parasitic precipitation losses arising from cyclotron and Landau interactions with whistler and ion cyclotron turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910025795&hterms=discrete+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddiscrete%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910025795&hterms=discrete+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddiscrete%2Bstructure"><span>A mathematical model of the structure and evolution of small-scale discrete <span class="hlt">auroral</span> arcs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Seyler, Charles E.</p> <p>1990-01-01</p> <p>A three-dimensional fluid model for the structure and evolution of small-scale discrete <span class="hlt">auroral</span> arcs originating from Alfven waves is developed and used to study the nonlinear macroscopic plasma dynamics of these <span class="hlt">auroral</span> arcs. The results of simulations show that stationary <span class="hlt">auroral</span> arcs can be unstable to a collisionless tearing mode which may be responsible for the observed transverse structuring in the form of folds and curls. At late times, the plasma becomes turbulent having transverse electric field power spectra that tend toward a universal k exp -5/3 spectral form.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GSL.....3...12M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GSL.....3...12M"><span>Relation of the <span class="hlt">auroral</span> substorm to the substorm current wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McPherron, Robert L.; Chu, Xiangning</p> <p>2016-12-01</p> <p>The <span class="hlt">auroral</span> substorm is an organized sequence of events seen in the aurora near midnight. It is a manifestation of the magnetospheric substorm which is a disturbance of the magnetosphere brought about by the solar wind transfer of magnetic flux from the dayside to the tail lobes and its return through the plasma sheet to the dayside. The most dramatic feature of the <span class="hlt">auroral</span> substorm is the sudden brightening and poleward expansion of the aurora. Intimately associated with this expansion is a westward electrical current flowing across the bulge of expanding aurora. This current is fed by a downward field-aligned current (FAC) at its eastern edge and an upward current at its western edge. This current system is called the substorm current wedge (SCW). The SCW forms within a minute of <span class="hlt">auroral</span> expansion. FAC are created by pressure gradients and field line bending from shears in plasma flow. Both of these are the result of pileup and diversion of plasma flows in the near-earth plasma sheet. The origins of these flows are reconnection sites further back in the tail. The <span class="hlt">auroral</span> expansion can be explained by a combination of a change in field line mapping caused by the substorm current wedge and a tailward growth of the outer edge of the pileup region. We illustrate this scenario with a complex substorm and discuss some of the problems associated with this interpretation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E.658G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E.658G"><span>Ultraviolet aurora on outer planets: morphology and remote sensing of <span class="hlt">electron</span> precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gerard, Jean-Claude; Bisikalo, Dmitry; Shematovich, Valery; Soret, Lauriane</p> <p>2016-07-01</p> <p>The aurora is the result of the interaction between energetic particles and the upper atmosphere of a planet. Generally, energetic particles from the magnetosphere penetrate the atmosphere, partly deposit their energy and are partly reflected. Their collisional interactions with the atmospheric atoms and molecules heat the atmosphere and produce <span class="hlt">auroral</span> emissions. Consequently, the aurora then bears the signature of both the acceleration mechanism and the atmospheric structure and composition. Jupiter's UV <span class="hlt">auroral</span> H2 and H emissions are generally divided into several components. The main <span class="hlt">auroral</span> emission at Jupiter is associated with the giant current loop connecting the region of co-rotation breakdown in the middle magnetosphere with the ionosphere. The polar emissions observed inside the main emission are very variable over short timescales. The observed diffuse emission equatorward of the main emission is most likely related to precipitation resulting from wave-particle interactions. Finally, the satellite magnetic footprints are created by accelerated <span class="hlt">electrons</span> resulting from the interaction between the Galilean moons and the plasma in the Jovian magnetosphere. Saturn's magnetosphere and its aurorae appear to be both solar wind driven as the terrestrial magnetosphere and rotationally dominated, similarly to Jupiter. In addition to the main <span class="hlt">auroral</span> ring, transient features have been recently identified. Uranus displays aurorae quite different from the other two with faint small-size structures appearing following solar storm activity. These different processes are probably associated with different energy spectra of the precipitated <span class="hlt">electrons</span>. We present an overview of recent results concerning the relation between morphology, variability and remote sensing of the <span class="hlt">auroral</span> <span class="hlt">electron</span> energy in the different components. We show that mapping the UV color ratio is a powerful tool to globally characterize the <span class="hlt">electron</span> precipitation and the flux-energy relation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...10422613A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...10422613A"><span>Energy and pitch angle-dispersed <span class="hlt">auroral</span> <span class="hlt">electrons</span> suggesting a time-variable, inverted-V potential structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arnoldy, R. L.; Lynch, K. A.; Austin, J. B.; Kintner, P. M.</p> <p>1999-10-01</p> <p>High temporal resolution <span class="hlt">electron</span> detectors aboard the PHAZE II rocket flight have shown that the energy-dispersed, field-aligned bursts (FABs) are time coincident with pitch angle-dispersed <span class="hlt">electrons</span> having energies at the maximum voltage of the inverted-V potential. This modulation of the energetic inverted-V <span class="hlt">electrons</span> is superimposed upon an energy-diffused background resulting in a peak-to-valley ratio of ~2 for the pitch angle-dispersed <span class="hlt">electrons</span>. Since the characteristic energy of the FABs, the order of an eV, is considerably less than that of the plasma sheet <span class="hlt">electrons</span> (the order of a <span class="hlt">keV</span>) presumably falling through the inverted-V potential to create the discrete aurora, the modulation mechanism has to be independent of the <span class="hlt">electron</span> temperature. The mechanism must accelerate the cold <span class="hlt">electrons</span> over a range of energies from the inverted-V energy down to a few tens of eV. It must do this at the same time it is creating a population of hot, pitch angle-dispersed <span class="hlt">electrons</span> at the inverted-V energy. Both the energy dispersion of the FABs and the pitch angle dispersion of the inverted-V <span class="hlt">electrons</span> can be used to determine a source height assuming both populations start from the same source region at the same time. These calculations give source heights between 3500 and 5300 km for various events and disagreement between the two methods the order of 20%, which is within the rather substantial error limits of both calculations. A simple mechanism of providing a common start time for both populations of <span class="hlt">electrons</span> would be a turning on/off of a spatially limited (vertically), inverted-V potential. The energy-dispersed FABs can be reconstructed at rocket altitudes if one assumes that cold <span class="hlt">electrons</span> are accelerated to an energy determined by how much of the inverted-V potential they fall through when it is turned on. Similarly, the pitch angle-dispersed, inverted-V <span class="hlt">electrons</span> can be modeled at rocket altitudes if one assumes that the plasma sheet <span class="hlt">electrons</span> falling through</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010033251','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010033251"><span>Electromagnetic Waves and Bursty <span class="hlt">Electron</span> Acceleration: Implications from Freja</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Andersson, Laila; Ivchenko, N.; Wahlund, J.-E.; Clemmons, J.; Gustavsson, B.; Eliasson, L.</p> <p>2000-01-01</p> <p>Dispersive Alfven wave activity is identified in four dayside <span class="hlt">auroral</span> oval events measured by the Freja satellite. The events are characterized by ion injection, bursty <span class="hlt">electron</span> precipitation below about I <span class="hlt">keV</span>, transverse ion heating and broadband extremely low frequency (ELF) emissions below the lower hybrid cutoff frequency (a few kHz). The broadband emissions are observed to become more electrostatic towards higher frequencies. Large-scale density depletions/cavities, as determined by the Langmuir probe measurements, and strong electrostatic emissions are often observed simultaneously. A correlation study has been carried out between the E- and B-field fluctuations below 64 Hz (the dc instrument's upper threshold) and the characteristics of the precipitating <span class="hlt">electrons</span>. This study revealed that the energization of <span class="hlt">electrons</span> is indeed related to the broadband ELF emissions and that the electrostatic component plays a predominant role during very active magnetospheric conditions. Furthermore, the effect of the ELF electromagnetic emissions on the larger scale field-aligned current systems has been investigated, and it is found that such an effect cannot be detected. Instead, the Alfvenic activity creates a local region of field-aligned currents. It is suggested that dispersive Alfven waves set up these local field-aligned current regions and in turn trigger more electrostatic emissions during certain conditions. In these regions ions are transversely heated, and large-scale density depletions/cavities may be created during especially active periods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990009871&hterms=monographs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmonographs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990009871&hterms=monographs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmonographs"><span><span class="hlt">Auroral</span> Observations from the POLAR Ultraviolet Imager (UVI)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Germany, G. A.; Spann, J. F.; Parks, G. K.; Brittnacher, M. J.; Elsen, R.; Chen, L.; Lummerzheim, D.; Rees, M. H.</p> <p>1998-01-01</p> <p>Because of the importance of the <span class="hlt">auroral</span> regions as a remote diagnostic of near-Earth plasma processes and magnetospheric structure, spacebased instrumentation for imaging the <span class="hlt">auroral</span> regions have been designed and operated for the last twenty-five years. The latest generation of imagers, including those flown on the POLAR satellite, extends this quest for multispectral resolution by providing three separate imagers for the visible, ultraviolet, and X ray images of the aurora. The ability to observe extended regions allows imaging missions to significantly extend the observations available from in situ or groundbased instrumentation. The complementary nature of imaging and other observations is illustrated below using results from tile GGS Ultraviolet Imager (UVI). Details of the requisite energy and intensity analysis are also presented.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900049920&hterms=kaufmann&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D60%26Ntt%3Dkaufmann','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900049920&hterms=kaufmann&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D60%26Ntt%3Dkaufmann"><span>Mapping and distortions of <span class="hlt">auroral</span> structures in the quiet magnetosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufmann, Richard L.; Larson, Douglas J.; Lu, Chen</p> <p>1990-01-01</p> <p>The closed quiet magnetosphere model of Beard (1979) and Beard et al. (1982) is used to identify those features of commonly observed dayside auroras that can be explained by either of two processes: mapping distortions or distortions caused by nearby Birkeland currents. It is shown that single and multiple linear and hooked <span class="hlt">auroral</span> forms can be easily explained in terms of mapping distortions in a quiet magnetosphere. On the other hand, the shapes of bright twisted or folded <span class="hlt">auroral</span> forms can be more easily explained as distortions produced by localized Birkeland currents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018RuPhJ..60.2201Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018RuPhJ..60.2201Z"><span>A Combined Model of Charging of the Surface and Bulk of a Dielectric Target by <span class="hlt">Electrons</span> with the Energies 10-30 <span class="hlt">keV</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zykov, V. M.; Neiman, D. A.</p> <p>2018-04-01</p> <p>A physico-mathematical model of the processes of radiation-induced charging of dielectric materials with open surfaces, irradiated with monoenergetic <span class="hlt">electrons</span> in the energy range 10-30 <span class="hlt">keV</span>, is described. The model takes into account the relationship between the processes of surface and bulk charging for the given conditions of the experimental design, which accounts for the effect of anomalously long charging of dielectrics after the incident energy of primary <span class="hlt">electrons</span> during charging is reduced to below the second critical energy for the secondary <span class="hlt">electronic</span> emission coefficient. The initial fast phase of charging a high-resistivity dielectric material (Al2O3) is investigated. It is shown that as the incident <span class="hlt">electron</span> energy is approaching the second critical energy during charging, the secondary <span class="hlt">electronic</span> emission is partially suppressed due to negative charging of the open surface of the dielectric and formation of a near-surface inversion electrical field retarding the <span class="hlt">electronic</span> emission yield.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22493151-single-impacts-kev-fullerene-ions-free-standing-graphene-emission-ions-electrons-from-confined-volume','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22493151-single-impacts-kev-fullerene-ions-free-standing-graphene-emission-ions-electrons-from-confined-volume"><span>Single impacts of <span class="hlt">keV</span> fullerene ions on free standing graphene: Emission of ions and <span class="hlt">electrons</span> from confined volume</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Verkhoturov, Stanislav V.; Geng, Sheng; Schweikert, Emile A., E-mail: schweikert@chem.tamu.edu</p> <p></p> <p>We present the first data from individual C{sub 60} impacting one to four layer graphene at 25 and 50 <span class="hlt">keV</span>. Negative secondary ions and <span class="hlt">electrons</span> emitted in transmission were recorded separately from each impact. The yields for C{sub n}{sup −} clusters are above 10% for n ≤ 4, they oscillate with <span class="hlt">electron</span> affinities and decrease exponentially with n. The result can be explained with the aid of MD simulation as a post-collision process where sufficient vibrational energy is accumulated around the rim of the impact hole for sputtering of carbon clusters. The ionization probability can be estimated by comparing experimentalmore » yields of C{sub n}{sup −} with those of C{sub n}{sup 0} from MD simulation, where it increases exponentially with n. The ionization probability can be approximated with ejecta from a thermally excited (3700 K) rim damped by cluster fragmentation and <span class="hlt">electron</span> detachment. The experimental <span class="hlt">electron</span> probability distributions are Poisson-like. On average, three <span class="hlt">electrons</span> of thermal energies are emitted per impact. The thermal excitation model invoked for C{sub n}{sup −} emission can also explain the emission of <span class="hlt">electrons</span>. The interaction of C{sub 60} with graphene is fundamentally different from impacts on 3D targets. A key characteristic is the high degree of ionization of the ejecta.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5524379','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5524379"><span>Calculations of <span class="hlt">Electron</span> Inelastic Mean Free Paths. XI. Data for Liquid Water for Energies from 50 eV to 30 <span class="hlt">keV</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shinotsuka, H.; Da, B.; Tanuma, S.; Yoshikawa, H.; Powell, C. J.; Penn, D. R.</p> <p>2017-01-01</p> <p>We calculated <span class="hlt">electron</span> inelastic mean free paths (IMFPs) for liquid water from its optical energy-loss function (ELF) for <span class="hlt">electron</span> energies from 50 eV to 30 <span class="hlt">keV</span>. These calculations were made with the relativistic full Penn algorithm (FPA) that has been used for previous IMFP and <span class="hlt">electron</span> stopping-power calculations for many elemental solids. We also calculated IMFPs of water with three additional algorithms: the relativistic single-pole approximation (SPA), the relativistic simplified SPA, and the relativistic extended Mermin method. These calculations were made using the same optical ELF in order to assess any differences of the IMFPs arising from choice of the algorithm. We found good agreement among the IMFPs from the four algorithms for energies over 300 eV. For energies less than 100 eV, however, large differences became apparent. IMFPs from the relativistic TPP-2M equation for predicting IMFPs were in good agreement with IMFPs from the four algorithms for energies between 300 eV and 30 <span class="hlt">keV</span> but there was poorer agreement for lower energies. We calculated values of the static structure factor as a function of momentum transfer from the FPA. The resulting values were in good agreement with results from first-principles calculations and with inelastic X-ray scattering spectroscopy experiments. We made comparisons of our IMFPs with earlier calculations from authors who had used different algorithms and different ELF data sets. IMFP differences could then be analyzed in terms of the algorithms and the data sets. Finally, we compared our IMFPs with measurements of IMFPs and of a related quantity, the effective attenuation length (EAL). There were large variations in the measured IMFPs and EALs (as well as their dependence on <span class="hlt">electron</span> energy). Further measurements are therefore required to establish consistent data sets and for more detailed comparisons with calculated IMFPs. PMID:28751796</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28751796','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28751796"><span>Calculations of <span class="hlt">Electron</span> Inelastic Mean Free Paths. XI. Data for Liquid Water for Energies from 50 eV to 30 <span class="hlt">keV</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shinotsuka, H; Da, B; Tanuma, S; Yoshikawa, H; Powell, C J; Penn, D R</p> <p>2017-04-01</p> <p>We calculated <span class="hlt">electron</span> inelastic mean free paths (IMFPs) for liquid water from its optical energy-loss function (ELF) for <span class="hlt">electron</span> energies from 50 eV to 30 <span class="hlt">keV</span>. These calculations were made with the relativistic full Penn algorithm (FPA) that has been used for previous IMFP and <span class="hlt">electron</span> stopping-power calculations for many elemental solids. We also calculated IMFPs of water with three additional algorithms: the relativistic single-pole approximation (SPA), the relativistic simplified SPA, and the relativistic extended Mermin method. These calculations were made using the same optical ELF in order to assess any differences of the IMFPs arising from choice of the algorithm. We found good agreement among the IMFPs from the four algorithms for energies over 300 eV. For energies less than 100 eV, however, large differences became apparent. IMFPs from the relativistic TPP-2M equation for predicting IMFPs were in good agreement with IMFPs from the four algorithms for energies between 300 eV and 30 <span class="hlt">keV</span> but there was poorer agreement for lower energies. We calculated values of the static structure factor as a function of momentum transfer from the FPA. The resulting values were in good agreement with results from first-principles calculations and with inelastic X-ray scattering spectroscopy experiments. We made comparisons of our IMFPs with earlier calculations from authors who had used different algorithms and different ELF data sets. IMFP differences could then be analyzed in terms of the algorithms and the data sets. Finally, we compared our IMFPs with measurements of IMFPs and of a related quantity, the effective attenuation length (EAL). There were large variations in the measured IMFPs and EALs (as well as their dependence on <span class="hlt">electron</span> energy). Further measurements are therefore required to establish consistent data sets and for more detailed comparisons with calculated IMFPs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JGR...10628897V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JGR...10628897V"><span>Polar UVI observations of dayside <span class="hlt">auroral</span> transient events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vorobjev, V. G.; Yagodkina, O. I.; Sibeck, D. G.; Liou, K.; Meng, C.-I.</p> <p>2001-12-01</p> <p>We analyze Polar Ultraviolet Imager (UVI) observations of <span class="hlt">auroral</span> transient events (ATEs) in the dayside Northern Hemisphere. During 5 winter months in 1996 and 1997, we found 31 prenoon ATEs but only 13 afternoon events. Prenoon and afternoon event characteristics differ. Prenoon ATEs generally appear as bright spots of <span class="hlt">auroral</span> luminosity in the area from 0800 to 1000 magnetic local time (MLT) and 74.5° and 76.5° corrected geomagnetic latitude (CGL). Bright aurorae then quickly expand westward and poleward, accompanied by high-latitude magnetic impulsive events (MIE) and traveling convection vortices (TCV). Afternoon ATEs usually appear as a sudden intensification of aurorae in the area from 1400 to 1600 MLT and 75.5° to 78.5° CGL. Within 15-20 min the bright band of luminosity extends eastward to reach 2000-2100 MLT at 70°-72° CGL. Although midlatitude and low-latitude ground magnetograms in the evening sector record increases in the horizontal component of the magnetic field, no corresponding features occur at stations in the morning sector. Afternoon ATEs correspond to abrupt changes in the interplanetary magnetic field (IMF) orientation, but not to significant variations of the solar wind dynamic pressure, indicating that the <span class="hlt">auroral</span> transient events occur as part of the magnetospheric response to abrupt changes in the foreshock geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870056475&hterms=Thermoelectric+effect&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DThermoelectric%2Beffect','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870056475&hterms=Thermoelectric+effect&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DThermoelectric%2Beffect"><span>Theoretical study of the effect of ionospheric return currents on the <span class="hlt">electron</span> temperature</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schunk, R. W.; Sojka, J. J.; Bowline, M. D.</p> <p>1987-01-01</p> <p>A time-dependent, three-dimensional model of the high-altitude ionosphere is presently used to study the effects of field-aligned ionospheric return currents on <span class="hlt">auroral</span> <span class="hlt">electron</span> temperatures for different seasonal and solar cycle conditions, as well as for different upper boundary heat fluxes. The average, large scale, return current densities, which are a few microamps/sq m, are too small to affect <span class="hlt">auroral</span> <span class="hlt">electron</span> temperatures. The thermoelectric effect exhibits a pronounced solar cycle and seasonal dependence, and its heat transport corresponds to an upward flow of <span class="hlt">electron</span> energy which can be either a source or sink of <span class="hlt">electron</span> energy depending on altitude and geophysical conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780031606&hterms=hot+spot&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dhot%2Bspot','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780031606&hterms=hot+spot&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dhot%2Bspot"><span>Search for Jovian <span class="hlt">auroral</span> hot spots</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Atreya, S. K.; Barker, E. S.; Yung, Y. L.; Donahue, T. M.</p> <p>1977-01-01</p> <p><span class="hlt">Auroral</span> emission originating at the foot of the Io-associated flux tube at Jupiter has been detected with a high-resolution spectrometer/telescope on board the Orbiting Astronomical Observatory Copernicus. The emission intensity at Ly-alpha is found to be greater than 100 kR, and the emission is located at zenographic latitudes greater than 65 deg.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20180000745&hterms=application+spaces&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dapplication%2Bspaces','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20180000745&hterms=application+spaces&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dapplication%2Bspaces"><span>First Application of the Zeeman Technique to Remotely Measure <span class="hlt">Auroral</span> Electrojet Intensity From Space</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yee, J. H.; Gjerloev, J.; Wu, D.; Schwartz, M. J.</p> <p>2017-01-01</p> <p>Using the O2 118 GHz spectral radiance measurements obtained by the Microwave Limb Sounder instrument on board the Aura spacecraft, we demonstrate that the Zeeman effect can be used to remotely measure the magnetic field perturbations produced by the <span class="hlt">auroral</span> electrojet near the Hall current closure altitudes. Our derived current-induced magnetic field perturbations are found to be highly correlated with those coincidently obtained by ground magnetometers. These perturbations are also found to be linearly correlated with <span class="hlt">auroral</span> electrojet strength. The statistically derived polar maps of our measured magnetic field perturbation reveal a spatial-temporal morphology consistent with that produced by the Hall current during substorms and storms. With today's technology, a constellation of compact, low-power, high spectral-resolution cubesats would have the capability to provide high precision and spatiotemporal magnetic field samplings needed for <span class="hlt">auroral</span> electrojet measurements to gain insights into the spatiotemporal behavior of the <span class="hlt">auroral</span> electrojet system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA43B2648L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA43B2648L"><span>Ionospheric <span class="hlt">electron</span> heating associated with pulsating auroras: joint optical and PFISR observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, J.; Donovan, E.; Spanswick, E.; Reimer, A.; Hampton, D. L.; Varney, R. H.</p> <p>2017-12-01</p> <p>In a recent survey based upon Swarm satellite data, Liang et al. [2017] repeatedly identified a strong <span class="hlt">electron</span> temperature (Te) enhancement associated with the pulsating aurora at Swarm altitudes ( 460 km). The observation of Te enhancement is not contingent upon whether the pulsating patch is "on" or "off" at the satellite traversal epoch. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the 4D (space-time) variations of the Te enhancement in association with the pulsating aurora. In a long-lasting pulsating <span class="hlt">auroral</span> event on 19 March 2015, we identify strong Te enhancements ( 600-1200 K) in the upper F-region ionosphere ( 300-600 km altitude) in conjunction to the passage of pulsating auroras over PFISR beams. The spatial-temporal variations of PFISR Te enhancement are found to generally conform to the variations of pulsating auroras. However, collocated meridian spectrograph observations suggest that the pulsating auroras of interest are composed of energetic <span class="hlt">electron</span> precipitation with characteristic energy ≥10 <span class="hlt">keV</span>, which is not supposed to be efficient in heating <span class="hlt">electrons</span> in the upper F-region. On the other hand, only moderate (<27%) Ne enhancements are found in the upper F-region during the pulsating aurora and Te enhancement interval. There are also moderate Te enhancements ( 100 K) in the E-region accompanying the pulsating auroras, but no clue of Te enhancement is found in the lower F-region. Based upon the above observations and simulations using the model developed in Liang et al. [2017], we propose that thermal conduction from the topside ionosphere, led by magnetospheric heat fluxes, constitutes the most likely underlying mechanism for the upper F-region <span class="hlt">electron</span> heating associated with pulsating auroras. Such magnetospheric heat fluxes may be pertinent to one long-hypothesized feature of pulsating auroras, namely the existence of an enhanced low-energy plasma population in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990089688&hterms=hydra&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhydra','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990089688&hterms=hydra&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhydra"><span>Relationship of Topside Ionospheric Ion Outflows to <span class="hlt">Auroral</span> Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_19990089688'); toggleEditAbsImage('author_19990089688_show'); toggleEditAbsImage('author_19990089688_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_19990089688_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_19990089688_hide"></p> <p>1997-01-01</p> <p>The POLAR satellite often observes upflowing ionospheric ions (UFls) in and near the <span class="hlt">auroral</span> oval on southern perigee (approximately 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass-angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with <span class="hlt">auroral</span> forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the dusk side after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawn side during the recovery phase. The UFls showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below approximately 10 kHz, while no significant <span class="hlt">auroral</span> activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped <span class="hlt">auroral</span> kilometric radiation (AKR) signatures observed above approximately 200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument (EFI) were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating <span class="hlt">electrons</span> and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs. the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860007325','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860007325"><span>Global <span class="hlt">auroral</span> responses to magnetospheric compressions by shocks in the solar wind: Two case studies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Craven, J. D.; Frank, L. A.; Russell, C. T.; Smith, E. J.; Lepping, R. P.</p> <p>1985-01-01</p> <p>The global <span class="hlt">auroral</span> responses to shocks in the solar wind at Earth were studied. The z-component of the interplanetary magnetic field, Bz, is negative ahead and behind the first shock and positive for the second case. A sudden-commencement geomagnetic storm develops in each case, with maximum D sub st 190 nT. An immediate <span class="hlt">auroral</span> response is detected at all longitudes around the <span class="hlt">auroral</span> oval, in which <span class="hlt">auroral</span> luminosities increase by a factor of 2 to 3 with the first samples after each sudden commencement. The time delay in obtaining the first sample varies with local time from approx. 1 to 18 mins. No other significant variations in the aurora are associated with the immediate response. Beginning approx. 30 mins after each sudden commencement, the aurora becomes active and displays significant variations in its luminosity and spatial distribution. For Bz 0 an intense substorm develops. A sun-aligned transpolar arc forms when Bz 0, appearing first at local midnight as a polar arc and then lengthening sunward from the <span class="hlt">auroral</span> oval across the polar cap to noon at an average speed of approx. 1 km/sec.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM53A..08Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM53A..08Y"><span>Improving the Ionospheric <span class="hlt">Auroral</span> Conductance in a Global Ring Current Model and the Effects on the Ionospheric Electrodynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Jordanova, V. K.; McGranaghan, R. M.; Solomon, S. C.</p> <p>2017-12-01</p> <p>The ionospheric conductance, height-integrated electric conductivity, can regulate both the ionospheric electrodynamics and the magnetospheric dynamics because of its key role in determining the electric field within the coupled magnetosphere-ionosphere system. State-of-the-art global magnetosphere models commonly adopt empirical conductance calculators to obtain the <span class="hlt">auroral</span> conductance. Such specification can bypass the complexity of the ionosphere-thermosphere chemistry but on the other hand breaks the self-consistent link within the coupled system. In this study, we couple a kinetic ring current model RAM-SCB-E that solves for anisotropic particle distributions with a two-stream <span class="hlt">electron</span> transport code (GLOW) to more self-consistently compute the height-dependent electric conductivity, provided the <span class="hlt">auroral</span> <span class="hlt">electron</span> precipitation from the ring current model. Comparisons with the traditional empirical formula are carried out. It is found that the newly coupled modeling framework reveals smaller Hall and Pedersen conductance, resulting in a larger electric field. As a consequence, the subauroral polarization streams demonstrate a better agreement with observations from DMSP satellites. It is further found that the commonly assumed Maxwellian spectrum of the particle precipitation is not globally appropriate. Instead, a full precipitation spectrum resulted from wave particle interactions in the ring current accounts for a more comprehensive precipitation spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5126218-morphology-auroral-zone-radio-wave-scintillation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5126218-morphology-auroral-zone-radio-wave-scintillation"><span>Morphology of <span class="hlt">auroral</span> zone radio wave scintillation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Rino, C.L.; Matthews, S.J.</p> <p>1980-08-01</p> <p>This paper describes the morphology of midnight sector and morning sector <span class="hlt">auroral</span> zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation activity followed the general pattern of local magnetic activity. The most prominent feature in the nightime data is a localized amplitude and phase scintillation enhancement at the point where the propagation vector lies within an L shell. A geometrical effectmore » due to a dynamic slab of sheetlike structures in the F region is hypothesized as the source of his enhancement. The data have been sorted by magnetic activity, proximity to local midnight, and season. The general features of the data are in agreement with the accepted morphology of <span class="hlt">auroral</span> zone scintillation.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940018611','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940018611"><span>Computer assisted analysis of <span class="hlt">auroral</span> images obtained from high altitude polar satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Samadani, Ramin; Flynn, Michael</p> <p>1993-01-01</p> <p>Automatic techniques that allow the extraction of physically significant parameters from <span class="hlt">auroral</span> images were developed. This allows the processing of a much larger number of images than is currently possible with manual techniques. Our techniques were applied to diverse <span class="hlt">auroral</span> image datasets. These results were made available to geophysicists at NASA and at universities in the form of a software system that performs the analysis. After some feedback from users, an upgraded system was transferred to NASA and to two universities. The feasibility of user-trained search and retrieval of large amounts of data using our automatically derived parameter indices was demonstrated. Techniques based on classification and regression trees (CART) were developed and applied to broaden the types of images to which the automated search and retrieval may be applied. Our techniques were tested with DE-1 <span class="hlt">auroral</span> images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12190590','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12190590"><span>The role of lower-hybrid-wave collapse in the <span class="hlt">auroral</span> ionosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schuck, P W; Ganguli, G I; Kintner, P M</p> <p>2002-08-05</p> <p>In regions where lower-hybrid solitary structures (LHSS) are observed, the character of <span class="hlt">auroral</span> lower-hybrid turbulence (LHT) (0-20 kHz) is investigated using the amplitude probability distribution of the electric field. The observed probability distributions are accurately described by a Rayleigh distribution with two degrees of freedom. The statistics of the LHT exhibit no evidence of the global modulational instability or self-similar wave collapse. We conclude that nucleation and resonant scattering in preexisting density depletions are the processes responsible for LHSS in <span class="hlt">auroral</span> LHT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JPhCS.162a2005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JPhCS.162a2005C"><span>Nonequilibrium calculations of the role of <span class="hlt">electron</span> impact in the production of NO and its emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Campbell, L.; Brunger, M. J.</p> <p>2009-04-01</p> <p>We review our recent work on nonequilibrium modelling of the density of nitric oxide and its infrared emissions in the Earth's upper atmosphere. The aim of these studies was to investigate the contribution of <span class="hlt">electron</span> impact excitation to the NO density and the sensitivity of this process to the <span class="hlt">electron</span> impact cross sections. The results are compared with satellite measurements of NO densities in equatorial and <span class="hlt">auroral</span> high-latitude conditions and with rocket measurements of infrared emissions in <span class="hlt">auroral</span> conditions. Particular findings are that <span class="hlt">electron</span> impact excitation of N2 makes a significant contribution to the NO density at altitudes around 105 km and to <span class="hlt">auroral</span> infrared emissions for the (1 → 0) ground-state emission from NO. The sensitivity of the NO fundamental emissions to various measured and theoretical integral cross sections is investigated and found to be significant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050163121&hterms=open+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dopen%2Bsource','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050163121&hterms=open+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dopen%2Bsource"><span>Cusp and LLBL as Sources of the Isolated Dayside <span class="hlt">Auroral</span> Feature During Northward IMF</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, S.-W.; Gallagher, D. L.; Spann, J. F.; Mende, S. B.; Greenwald, R. A.; Newell, P. T.</p> <p>2004-01-01</p> <p>An intense dayside proton aurora was observed by Imager for Magnetopause-to- Aurora Global Exploration Far Ultra-Violet imager (IMAGE FUV) for an extensive period of northward interplanetary magnetic field (IMF) on 17 and 18 September 2000. This aurora partially coincided with the <span class="hlt">auroral</span> oval and intruded farther poleward into the polar cap, and it showed longitudinal motions in response to IMF By variation. Intense magnetosheath-like <span class="hlt">electron</span> and ion precipitations have been simultaneously detected by Defense Meteorological Satellite Program (DMSP) above the poleward portion of the high-latitude dayside aurora. They resemble the typical plasmas observed in the low-altitude cusp. However, less intense <span class="hlt">electrons</span> and more energetic ions were detected over the equatonvard part of the aurora. These plasmas are closer to the low-latitude boundary layer (LLBL) plasmas. Under strongly northward IMF, global ionospheric convection derived from Super Dual <span class="hlt">Auroral</span> Radar Network (SuperDARN) radar measurements showed a four-cell pattern with sunward convection in the middle of the dayside polar cap and the dayside aurora corresponded to two different convection cells. This result further supports two source regions for the aurora. The cusp proton aurora is on open magnetic field lines convecting sunward whereas the LLBL proton aurora is on closed field lines convecting antisunward. These IMAGE, DMSP, and SuperDARN observations reveal the structure and dynamics of the aurora and provide strong evidence for magnetic merging occurring at the high-latitude magnetopause poleward from the cusp. This merging process was very likely quasi-stationary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740018764','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740018764"><span>Rocket investigations of the <span class="hlt">auroral</span> electrojet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, T. N.</p> <p>1973-01-01</p> <p>Five Nike-Tomahawk rockets were flown to measure perturbations in the magnitude of the geomagnetic field due to <span class="hlt">auroral</span> electrojets. The dates and locations of the rocket launches are given along with a brief explanation of payloads and instrumentation. Papers published as a result of the project are listed. An abstract is included which outlines the scientific results from one of the flights.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/909921','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/909921"><span>Thermoluminescent response of LiF (TLD-100) to 5-30 <span class="hlt">keV</span> <span class="hlt">electrons</span> and the effect of annealing in various atmospheres.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lasky, J B; Moran, P R</p> <p>1977-09-01</p> <p>The response of single crystal and extruded ribbons of TLD-100 to 5-30 <span class="hlt">keV</span> <span class="hlt">electrons</span> was investigated. If annealing is done in a vacuum, the sensitivity of TLD-100 single crystals to these <span class="hlt">electrons</span> and the resultant glow curve are essentially the same as when irradiation are carried out with 137Cs gamma rays. All discrepancies in sensitivity can then be accounted for by the higher LET of <span class="hlt">electrons</span>. The commonly used 'standard annealing' at 400 degrees C for one hour produced a change in the glow curve shape and a loss in sensitivity in contrast to the vacuum anneal results. Diffusion of hydroxyl ions into the sample during air annealing is believed to be the primary cause for this change. These results explain the source of the 'dead layer' proposed to explain the variation with particle size of the luminescent efficiency of X-ray irradiated TLD-100 powder and the low TL efficiency from low energy <span class="hlt">electron</span> irradiations. With the use of the vacuum annealing procedure, the same sensitivity and reproducibility can be achieved for the dosimetry of low energy <span class="hlt">electrons</span> and other shallowly penetrating radiation as is currently achieved for the dosimetry of X-rays.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPlPh..81b9004E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPlPh..81b9004E"><span>Effect of <span class="hlt">electron</span> beam on the properties of <span class="hlt">electron</span>-acoustic rogue waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>El-Shewy, E. K.; Elwakil, S. A.; El-Hanbaly, A. M.; Kassem, A. I.</p> <p>2015-04-01</p> <p>The properties of nonlinear <span class="hlt">electron</span>-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold <span class="hlt">electron</span> fluid, Maxwellian hot <span class="hlt">electrons</span>, an <span class="hlt">electron</span> beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles and the associated electric field on the carrier wave number, normalized density of hot <span class="hlt">electron</span> and <span class="hlt">electron</span> beam, relative cold <span class="hlt">electron</span> temperature and relative beam temperature are discussed. The results of the present investigation may be applicable in <span class="hlt">auroral</span> zone plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24144616','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24144616"><span>Calculations of stopping powers and inelastic mean free paths for 20 eV-20 <span class="hlt">keV</span> <span class="hlt">electrons</span> in 11 types of human tissue.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tan, Zhenyu; Liu, Wei</p> <p>2013-12-01</p> <p>Systematic calculations are performed for determining the stopping powers (SP) and inelastic mean free paths (IMFP) for 20 eV-20 <span class="hlt">keV</span> <span class="hlt">electrons</span> in 11 types of human tissue. The calculations are based on a dielectric model, including the Born-Ochkur exchange correction. The optical energy loss functions (OELF) are empirically evaluated, because of the lack of available experimental optical data for the 11 tissues under consideration. The evaluated OELFs are examined by the f-sum rule expected from the dielectric response theory, and by calculation of the mean excitation energy. The calculated SPs are compared with those for PMMA (polymethylmethacrylate, a tissue equivalent material) and liquid water. The SP and IMFP data presented here are the results for the 11 human tissues over the energy range of 20 eV-20 <span class="hlt">keV</span>, and are of importance in radiotherapy planning and for studies of various radiation effects on human tissues. © 2013 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRA..118..685I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRA..118..685I"><span>The Heppner-Maynard Boundary measured by SuperDARN as a proxy for the latitude of the <span class="hlt">auroral</span> oval</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Imber, S. M.; Milan, S. E.; Lester, M.</p> <p>2013-02-01</p> <p>We present a statistical study relating the latitude of the <span class="hlt">auroral</span> oval measured by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) SI-12 proton <span class="hlt">auroral</span> camera to that of the Heppner-Maynard Boundary (HMB) determined from Super Dual <span class="hlt">Auroral</span> Radar Network (SuperDARN) data during the period 2000-2002. The HMB represents the latitudinal extent of the ionospheric convection pattern. The oval latitude from the proton <span class="hlt">auroral</span> images is determined using the method of Milan et al. (2009a), which fits a circle centered on a point 2° duskward and 5° antisunward of the magnetic pole. The <span class="hlt">auroral</span> latitude at midnight is determined for those images where the concurrent SuperDARN northern hemisphere maps contain more than 200 data points such that the HMB is well-defined. The statistical study comprises over 198,000 two-minute intervals, and we find that the HMB is located on average 2.2° equatorward of the proton <span class="hlt">auroral</span> latitude. A superposed epoch analysis of over 2500 substorms suggests that the separation between the HMB and the oval latitude increases slightly during periods of high geomagnetic activity. We suggest that during intervals where there are no <span class="hlt">auroral</span> images available, the HMB latitude and motion could be used as a proxy for that of the aurora, and therefore provide information about motions of the open/closed field line boundary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RaPC..141...17L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RaPC..141...17L"><span>Lα and Mαβ X-ray production cross-sections of Bi by 6-30 <span class="hlt">keV</span> <span class="hlt">electron</span> impact</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Y.; Xu, M. X.; Yuan, Y.; Wu, Y.; Qian, Z. C.; Chang, C. H.; Mei, C. S.; Zhu, J. J.; Moharram, K.</p> <p>2017-12-01</p> <p>In this paper, the Lα and Mαβ X-ray production cross-sections for Bi impacted by 6-30 <span class="hlt">keV</span> <span class="hlt">electron</span> have been measured. The experiments were performed at a Scanning <span class="hlt">Electron</span> Microscope equipped with a silicon drift detector. The thin film with thick C substrate and the thin film deposited on self-supporting thin C film were both used as the targets to make a comparison. For the thick carbon substrate target, the Monte Carlo method has been used to eliminate the contribution of backscattering particles. The measured data are compared with the DWBA theoretical model and the experimental results in the literature. The experimental data for the thin film with thick C substrate target and the thin film deposited on self-supporting thin C film target are within reasonable gaps. The DWBA theoretical model gives good fit to the experimental data both for L- and M- shells. Besides, we also analyze the reasons why the discrepancies exist between our measurements and the experimental results in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...10520857C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...10520857C"><span>Nitric oxide excited under <span class="hlt">auroral</span> conditions: Excited state densities and band emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cartwright, D. C.; Brunger, M. J.; Campbell, L.; Mojarrabi, B.; Teubner, P. J. O.</p> <p>2000-09-01</p> <p><span class="hlt">Electron</span> impact excitation of vibrational levels in the ground <span class="hlt">electronic</span> state and nine excited <span class="hlt">electronic</span> states in NO has been simulated for an IBC II aurora (i.e., ˜10 kR in 3914 Å radiation) in order to predict NO excited state number densities and band emission intensities. New integral <span class="hlt">electron</span> impact excitation cross sections for NO were combined with a measured IBC II <span class="hlt">auroral</span> secondary <span class="hlt">electron</span> distribution, and the vibrational populations of 10 NO <span class="hlt">electronic</span> states were determined under conditions of statistical equilibrium. This model predicts an extended vibrational distribution in the NO ground <span class="hlt">electronic</span> state produced by radiative cascade from the seven higher-lying doublet excited <span class="hlt">electronic</span> states populated by <span class="hlt">electron</span> impact. In addition to significant energy storage in vibrational excitation of the ground <span class="hlt">electronic</span> state, both the a 4Π and L2 Φ excited <span class="hlt">electronic</span> states are predicted to have relatively high number densities because they are only weakly connected to lower <span class="hlt">electronic</span> states by radiative decay. Fundamental mode radiative transitions involving the lowest nine excited vibrational levels in the ground <span class="hlt">electronic</span> state are predicted to produce infrared (IR) radiation from 5.33 to 6.05 μm with greater intensity than any single NO <span class="hlt">electronic</span> emission band. Fundamental mode radiative transitions within the a 4Π <span class="hlt">electronic</span> state, in the 10.08-11.37 μm region, are predicted to have IR intensities comparable to individual <span class="hlt">electronic</span> emission bands in the Heath and ɛ band systems. Results from this model quantitatively predict the vibrational quantum number dependence of the NO IR measurements of Espy et al. [1988].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840033231&hterms=generation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeneration%2BZ','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840033231&hterms=generation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeneration%2BZ"><span>Cyclotron maser emission of <span class="hlt">auroral</span> Z mode radiation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Melrose, D. B.; Hewitt, R. G.; Dulk, G. A.</p> <p>1983-01-01</p> <p>Results are presented suggesting that loss cone driven cyclotron maser emission by upgoing <span class="hlt">electrons</span>, closely analogous to <span class="hlt">auroral</span> kilometric radiation (AKR), may be the mechanism behind the observed Z mode radiation. With this hypothesis, the lack of a strong correlation between the Z mode radiation and AKR is not surprising; the ray paths for the X mode and the Z mode are markedly different, with the former directed upward and the latter downward. In addition, it is expected that the generation of the Z mode will be favored only in regions where the ratio of the plasma frequency to the <span class="hlt">electron</span> cyclotron frequency is greater than or approximately equal to 0.3, that is, where the X mode radiation is suppressed. If the fraction of the radiation generated that crosses the cyclotron layer is large, then the argument in favor of the loss cone driven cyclotron maser as the source of the observed Z mode radiation is a strong one. The spatial growth rates are fairly large in comparison with those for the X mode, and there seems to be little doubt that Z mode radiation should be generated under conditions that differ only slightly from those for the generation of X mode radiation in AKR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983JGR....8810065M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983JGR....8810065M"><span>Cyclotron maser emission of <span class="hlt">auroral</span> Z mode radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Melrose, D. B.; Hewitt, R. G.; Dulk, G. A.</p> <p>1983-12-01</p> <p>Results are presented suggesting that loss cone driven cyclotron maser emission by upgoing <span class="hlt">electrons</span>, closely analogous to <span class="hlt">auroral</span> kilometric radiation (AKR), may be the mechanism behind the observed Z mode radiation. With this hypothesis, the lack of a strong correlation between the Z mode radiation and AKR is not surprising; the ray paths for the X mode and the Z mode are markedly different, with the former directed upward and the latter downward. In addition, it is expected that the generation of the Z mode will be favored only in regions where the ratio of the plasma frequency to the <span class="hlt">electron</span> cyclotron frequency is greater than or approximately equal to 0.3, that is, where the X mode radiation is suppressed. If the fraction of the radiation generated that crosses the cyclotron layer is large, then the argument in favor of the loss cone driven cyclotron maser as the source of the observed Z mode radiation is a strong one. The spatial growth rates are fairly large in comparison with those for the X mode, and there seems to be little doubt that Z mode radiation should be generated under conditions that differ only slightly from those for the generation of X mode radiation in AKR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSH43B2578H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSH43B2578H"><span>ISIS/EPI-Lo: A New Instrument for Measuring <span class="hlt">keV</span> to MeV Ions and <span class="hlt">Electrons</span> with Simultaneous Half-Sky Coverage on NASA's Solar Probe Plus Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hill, M. E.; Mitchell, D. G.; McNutt, R. L., Jr.; Cooper, S.; Crew, A. B.; Dupont, A.; Hayes, J.; Hoffer, E.; Nelson, K.; Parker, C.; Schlemm, C., II; Seifert, H.; Stokes, M.; Angold, N. G.; McComas, D. J.; Weidner, S.; Wiedenbeck, M. E.</p> <p>2016-12-01</p> <p>The Solar Probe Plus (SPP) Mission's Integrated Science Investigation of the Sun (ISIS) is a suite of two energetic particle instruments, EPI-Lo and EPI-Hi, covering lower ( 10 <span class="hlt">keV</span>-100 MeV) and higher ( 1-100 MeV/nuc) energies, respectively. The ISIS team will investigate the origins, acceleration, and transport of energetic particles in the corona and inner heliosphere during the planned 7-year, 24-orbit mission, with a perihelion initially of 0.16 AU (36 Solar radii; RS), the three final orbits reaching 0.044 AU (9.9 RS). EPI-Lo has a novel approach to obtaining large angular coverage, well-suited to 3-axis stabilized spacecraft such as SPP, by densely sampling its 2π steradian field of view with 80 apertures organized in eight matching, 10-aperture wedges. Each wedge relies primarily on time-of-flight (TOF) mass spectrometer techniques, employing thin secondary-<span class="hlt">electron</span>-emitting foils, microchannel plates, and solid state detectors (SSDs), to measure ions from 50 <span class="hlt">keV</span> - 15 MeV and <span class="hlt">electrons</span> from 50-500 <span class="hlt">keV</span>. Signal attenuation, absorbers, TOF-only measurements, and SSD-only techniques are used to extend this energy range higher and lower. In 2015 and 2016 we made measurements with engineering units and flight-spare EPI-Lo wedges at accelerators and with radioactive sources; in addition to presenting the instrument design, we will report the results from these tests to characterize the instrument's measurement performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720048295&hterms=pitch+detector&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dpitch%2Bdetector','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720048295&hterms=pitch+detector&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dpitch%2Bdetector"><span>Anisotropic pitch angle distribution of 50 eV to 50 <span class="hlt">keV</span> particles at synchronous altitude.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deforest, S. E.; Mcilwain, C. F.</p> <p>1972-01-01</p> <p>At times, the <span class="hlt">electron</span> pitch angle distributions at synchronous orbit have been observed to be highly anisotropic. In the local morning region, distributions concentrated near 90 deg are often observed in particles of less than approximately 2000 V. This anisotropy decreases with increasing energy from 1 <span class="hlt">keV</span> to the detector's limit at 50 <span class="hlt">keV</span>. The time development of anisotropy is consistent with production by pitch angle scattering processes which are not effective on <span class="hlt">electrons</span> with small velocities parallel to the magnetic field. Another type of distribution has been observed with the low-energy (below 1000 V) <span class="hlt">electrons</span> concentrated parallel and antiparallel to the magnetic field. These distributions are only seen in the dusk sector, but this may be an orbital artifact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850027204','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850027204"><span>Two-dimensional quasineutral description of particles and fields above discrete <span class="hlt">auroral</span> arcs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Newman, A. L.; Chiu, Y. T.; Cornwall, J. M.</p> <p>1985-01-01</p> <p>Stationary hot and cool particle distributions in the <span class="hlt">auroral</span> magnetosphere are modelled using adiabatic assumptions of particle motion in the presence of broad-scale electrostatic potential structure. The study has identified geometrical restrictions on the type of broadscale potential structure which can be supported by a multispecies plasma having specified sources and energies. Without energization of cool thermal ionospheric <span class="hlt">electrons</span>, a substantial parallel potential drop cannot be supported down to altitudes of 2000 km or less. Observed upward-directed field-aligned currents must be closed by return currents along field lines which support little net potential drop. In such regions the plasma density appears significantly enhanced. Model details agree well with recent broad-scale implications of satellite observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM41A2664C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM41A2664C"><span>ISINGLASS <span class="hlt">Auroral</span> Sounding Rocket Campaign Data Synthesis: Radar, Imagery, and In Situ Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clayton, R.; Lynch, K. A.; Evans, T.; Hampton, D. L.; Burleigh, M.; Zettergren, M. D.; Varney, R. H.; Reimer, A.; Hysell, D. L.; Michell, R.; Samara, M.; Grubbs, G. A., II</p> <p>2017-12-01</p> <p>E-field and flow variations across <span class="hlt">auroral</span> arc boundaries are typically sub-grid measurements for ground based sensors such as radars and imagers, even for quiet stable arcs. In situ measurements can provide small scale resolution, but only provide a snapshot at a localized time and place. Using ground based and in situ measurements of the ISINGLASS <span class="hlt">auroral</span> sounding rocket campaign in conjunction, we use the in situ measurements to validate ground based synthesis of these small scale observations based on the classification of <span class="hlt">auroral</span> arcs in Marklund(1984). With validation of this technique, sub-grid information can be gained from radar data using particular visible <span class="hlt">auroral</span> features during times where only ground based measurements are present. The ISINGLASS campaign (Poker Flat Alaska, Winter 2017) included the nights of Feb 22 2017 and Mar 02 2017, which possessed multiple stable arc boundaries that can be used for synthesis, including the two events into which the ISINGLASS rockets were launched. On Mar 02 from 0700 to 0800 UT, two stable slowly southward-propagating <span class="hlt">auroral</span> arcs persisted within the instrument field of view, and lasted for a period of >15min. The second of these events contains the 36.304 rocket trajectory, while both events have full ground support from camera imagery and radar. Data synthesis from these events is accomplished using Butler (2010), Vennell (2009), and manually selected <span class="hlt">auroral</span> boundaries from ground based cameras. With determination of the <span class="hlt">auroral</span> arc boundaries from ground based imagery, a prediction of the fields along the length of a long straight arc boundary can be made using the ground based radar data, even on a sub-radar-grid scale, using the Marklund arc boundary classification. We assume that fields everywhere along a long stable arc boundary should be the same. Given a long stable arc, measurements anywhere along the arc (i.e. from PFISR) can be replicated along the length of the boundary. This prediction can then</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JKPS...72.1086S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JKPS...72.1086S"><span>HEPD on NEXTSat-1: A High Energy Particle Detector for Measurements of Precipitating Radiation Belt <span class="hlt">Electrons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sohn, Jongdae; Lee, Jaejin; Min, Kyoungwook; Lee, Junchan; Lee, Seunguk; Lee, Daeyoung; Jo, Gyeongbok; Yi, Yu; Na, Gowoon; Kang, Kyung-In; Shin, Goo-Hwan</p> <p>2018-05-01</p> <p>Radiation belt particles of the inner magnetosphere precipitate into the atmosphere in the subauroral regions when they are pitch-angle scattered into the loss cone by wave-particle interactions. Such particle precipitations are known to be especially enhanced during space storms, though they can also occur during quiet times. The observed characteristics of precipitating <span class="hlt">electrons</span> can be distinctively different, in their time series as well as in their spectra, depending on the waves involved. The present paper describes the High Energy Particle Detector (HEPD) on board the Next Generation Small Satellite-1 (NEXTSat-1), which will measure these radiation belt <span class="hlt">electrons</span> from a low-Earth polar orbit satellite to study the mechanisms related to <span class="hlt">electron</span> precipitation in the sub-<span class="hlt">auroral</span> regions. The HEPD is based on silicon barrier detectors and consists of three telescopes that are mounted on the satellite to have angles of 0°. 45°, and 90°, respectively with the local geomagnetic field during observations. With a high time resolution of 32 Hz and a high spectral resolution of 11 channels over the energy range from 350 <span class="hlt">keV</span> to 2 MeV, together with the pitch angle information provided by the three telescopes, HEPD is capable of identifying physical processes, such as microbursts and dust-side relativistic <span class="hlt">electron</span> precipitation (DREP) events associated with <span class="hlt">electron</span> precipitations. NextSat-1 is scheduled for launch in early 2018.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NIMPB.394..103H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NIMPB.394..103H"><span>A comparative study of inelastic scattering models at energy levels ranging from 0.5 <span class="hlt">keV</span> to 10 <span class="hlt">keV</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Chia-Yu; Lin, Chun-Hung</p> <p>2017-03-01</p> <p>Six models, including a single-scattering model, four hybrid models, and one dielectric function model, were evaluated using Monte Carlo simulations for aluminum and copper at incident beam energies ranging from 0.5 <span class="hlt">keV</span> to 10 <span class="hlt">keV</span>. The inelastic mean free path, mean energy loss per unit path length, and backscattering coefficients obtained by these models are compared and discussed to understand the merits of the various models. ANOVA (analysis of variance) statistical models were used to quantify the effects of inelastic cross section and energy loss models on the basis of the simulated results deviation from the experimental data for the inelastic mean free path, the mean energy loss per unit path length, and the backscattering coefficient, as well as their correlations. This work in this study is believed to be the first application of ANOVA models towards evaluating inelastic <span class="hlt">electron</span> beam scattering models. This approach is an improvement over the traditional approach which involves only visual estimation of the difference between the experimental data and simulated results. The data suggests that the optimization of the effective <span class="hlt">electron</span> number per atom, binding energy, and cut-off energy of an inelastic model for different materials at different beam energies is more important than the selection of inelastic models for Monte Carlo <span class="hlt">electron</span> scattering simulation. During the simulations, parameters in the equations should be tuned according to different materials for different beam energies rather than merely employing default parameters for an arbitrary material. Energy loss models and cross-section formulas are not the main factors influencing energy loss. Comparison of the deviation of the simulated results from the experimental data shows a significant correlation (p < 0.05) between the backscattering coefficient and energy loss per unit path length. The inclusion of backscattering <span class="hlt">electrons</span> generated by both primary and secondary <span class="hlt">electrons</span> for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AnGeo..32..623X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AnGeo..32..623X"><span>An empirical model of the <span class="hlt">auroral</span> oval derived from CHAMP field-aligned current signatures - Part 2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, C.; Lühr, H.</p> <p>2014-06-01</p> <p>In this paper we introduce a new model for the location of the <span class="hlt">auroral</span> oval. The <span class="hlt">auroral</span> boundaries are derived from small- and medium-scale field-aligned current (FAC) based on the high-resolution CHAMP (CHAllenging Minisatellite Payload) magnetic field observations during the years 2000-2010. The basic shape of the <span class="hlt">auroral</span> oval is controlled by the dayside merging electric field, Em, and can be fitted well by ellipses at all levels of activity. All five ellipse parameters show a dependence on Em which can be described by quadratic functions. Optimal delay times for the merging electric field at the bow shock are 30 and 15 min for the equatorward and poleward boundaries, respectively. A comparison between our model and the British Antarctic Survey (BAS) <span class="hlt">auroral</span> model derived from IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) optical observations has been performed. There is good agreement between the two models regarding both boundaries, and the differences show a Gaussian distribution with a width of ±2° in latitude. The difference of the equatorward boundary shows a local-time dependence, which is 1° in latitude poleward in the morning sector and 1° equatorward in the afternoon sector of the BAS model. We think the difference between the two models is caused by the appearance of <span class="hlt">auroral</span> forms in connection with upward FACs. All information required for applying our <span class="hlt">auroral</span> oval model (CH-Aurora-2014) is provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1525..138C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1525..138C"><span>Diagnostics for the optimization of an 11 <span class="hlt">keV</span> inverse Compton scattering x-ray source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauchat, A.-S.; Brasile, J.-P.; Le Flanchec, V.; Nègre, J.-P.; Binet, A.; Ortega, J.-M.</p> <p>2013-04-01</p> <p>In a scope of a collaboration between Thales Communications & Security and CEA DAM DIF, 11 <span class="hlt">keV</span> Xrays were produced by inverse Compton scattering on the ELSA facility. In this type of experiment, X-ray observation lies in the use of accurate <span class="hlt">electron</span> and laser beam interaction diagnostics and on fitted X-ray detectors. The low interaction probability between < 100 μm width, 12 ps [rms] length <span class="hlt">electron</span> and photon pulses requires careful optimization of pulse spatial and temporal covering. Another issue was to observe 11 <span class="hlt">keV</span> X-rays in the ambient radioactive noise of the linear accelerator. For that, we use a very sensitive detection scheme based on radio luminescent screens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ChPhC..38d4001H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ChPhC..38d4001H"><span>Evaluation of the 1077 <span class="hlt">keV</span> γ-ray emission probability from 68Ga decay</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Xiao-Long; Jiang, Li-Yang; Chen, Xiong-Jun; Chen, Guo-Chang</p> <p>2014-04-01</p> <p>68Ga decays to the excited states of 68Zn through the <span class="hlt">electron</span> capture decay mode. New recommended values for the emission probability of 1077 <span class="hlt">keV</span> γ-ray given by the ENSDF and DDEP databases all use data from absolute measurements. In 2011, JIANG Li-Yang deduced a new value for 1077 <span class="hlt">keV</span> γ-ray emission probability by measuring the 69Ga(n,2n) 68Ga reaction cross section. The new value is about 20% lower than values obtained from previous absolute measurements and evaluations. In this paper, the discrepancies among the measurements and evaluations are analyzed carefully and the new values are re-recommended. Our recommended value for the emission probability of 1077 <span class="hlt">keV</span> γ-ray is (2.72±0.16)%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21185967-effect-electron-irradiation-dose-performance-avalanche-photodiode-electron-detectors','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21185967-effect-electron-irradiation-dose-performance-avalanche-photodiode-electron-detectors"><span>Effect of <span class="hlt">electron</span> irradiation dose on the performance of avalanche photodiode <span class="hlt">electron</span> detectors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kawauchi, Taizo; Wilde, Markus; Fukutani, Katsuyuki</p> <p>2009-01-01</p> <p>Avalanche photodiodes (APDs) are efficient detectors for <span class="hlt">electrons</span> with energies below 100 <span class="hlt">keV</span>. The damaging effects of 8 <span class="hlt">keV</span> <span class="hlt">electron</span> beam irradiation on the dark current and the output signal of the APD detector were investigated in this study. The APD dark current increases after <span class="hlt">electron</span> doses exceeding 1.4x10{sup 13} cm{sup -2}. Preirradiation by high doses of 8 <span class="hlt">keV</span> <span class="hlt">electrons</span> further causes a deformation of the pulse height distribution of the APD output in the subsequent detection of low-flux <span class="hlt">electrons</span>. This effect is particularly prominent when the energy of the detected <span class="hlt">electrons</span> is lower than that of the damaging <span class="hlt">electrons</span>.more » By comparing the experimental data with results of a simulation based on an <span class="hlt">electron</span> trapping model, we conclude that the degradation of the APD performance is attributable to an enhancement of secondary-<span class="hlt">electron</span> trapping at irradiation induced defects.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5131847','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5131847"><span>Magnetotail energy dissipation during an <span class="hlt">auroral</span> substorm</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Panov, E.V.; Baumjohann, W.; Wolf, R.A.; Nakamura, R.; Angelopoulos, V.; Weygand, J. M.; Kubyshkina, M.V.</p> <p>2016-01-01</p> <p>Violent releases of space plasma energy from the Earth’s magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal <span class="hlt">auroral</span> arcs that move equatorward at a velocity of about 1km/s. This observed <span class="hlt">auroral</span> activity appears sufficient to dissipate the released energy. PMID:27917231</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM23A2536H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM23A2536H"><span>Evolution of <span class="hlt">auroral</span> acceleration region field-aligned current systems, plasma, and potentials observed by Cluster during substorms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hull, A. J.; Chaston, C. C.; Fillingim, M. O.; Frey, H. U.; Goldstein, M. L.; Bonnell, J. W.; Mozer, F.</p> <p>2015-12-01</p> <p>The <span class="hlt">auroral</span> acceleration region is an integral link in the chain of events that transpire during substorms, and the currents, plasma and electric fields undergo significant changes driven by complex dynamical processes deep in the magnetotail. The acceleration processes that occur therein accelerate and heat the plasma that ultimately leads to some of the most intense global substorm <span class="hlt">auroral</span> displays. Though this region has garnered considerable attention, the temporal evolution of field-aligned current systems, associated acceleration processes, and resultant changes in the plasma constituents that occur during key stages of substorm development remain unclear. In this study we present a survey of Cluster traversals within and just above the <span class="hlt">auroral</span> acceleration region (≤3 Re altitude) during substorms. Particular emphasis is on the spatial morphology and developmental sequence of <span class="hlt">auroral</span> acceleration current systems, potentials and plasma constituents, with the aim of identifying controlling factors, and assessing <span class="hlt">auroral</span> emmission consequences. Exploiting multi-point measurements from Cluster in combination with <span class="hlt">auroral</span> imaging, we reveal the injection powered, Alfvenic nature of both the substorm onset and expansion of <span class="hlt">auroral</span> particle acceleration. We show evidence that indicates substorm onsets are characterized by the gross-intensification and filamentation/striation of pre-existing large-scale current systems to smaller/dispersive scale Alfven waves. Such an evolutionary sequence has been suggested in theoretical models or single spacecraft data, but has not been demonstrated or characterized in multispacecraft observations until now. It is also shown how the Alfvenic variations over time may dissipate to form large-scale inverted-V structures characteristic of the quasi-static aurora. These findings suggest that, in addition to playing active roles in driving substorm aurora, inverted-V and Alfvenic acceleration processes are causally linked. Key</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P24A..08S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P24A..08S"><span>High spatial and spectral resolution measurements of Jupiter's <span class="hlt">auroral</span> regions using Gemini-North-TEXES</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Lacy, J.; Giles, R.; Fletcher, L. N.; Vogt, M.; Irwin, P. G.</p> <p>2017-12-01</p> <p>Jupiter exhibits <span class="hlt">auroral</span> emission at a multitude of wavelengths. <span class="hlt">Auroral</span> emission at X-ray, ultraviolet and near-infrared wavelengths demonstrate the precipitation of ion and <span class="hlt">electrons</span> in Jupiter's upper atmosphere, at altitudes exceeding 250 km above the 1-bar level. Enhanced mid-infrared emission of CH4, C2H2, C2H4 and further hydrocarbons is also observed coincident with Jupiter's <span class="hlt">auroral</span> regions. Retrieval analyses of infrared spectra from IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility) indicate strong heating at the 1-mbar level and evidence of ion-neutral chemistry, which enriches the abundances of unsaturated hydrocarbons (Sinclair et al., 2017b, doi:10.1002/2017GL073529, Sinclair et al., 2017c (under review)). The extent to which these phenomena in the stratosphere are correlated and coupled physically with the shorter-wavelength <span class="hlt">auroral</span> emission originating from higher altitudes has been a challenge due to the limited spatial resolution available on the IRTF. Smaller-scale features observed in the near-infrared and ultraviolet emission, such as the main `oval', transient `swirls' and dusk-active regions within the main oval (e.g. Stallard et al., 2014, doi:10.1016/j/Icarus.2015.12.044, Nichols et al., 2017, doi: 10.1002/2017GL073029) are potentially being blurred in the mid-infrared by the diffraction-limited resolution (0.7") of IRTF's 3-metre primary aperture. However, on March 17-19th 2017, we obtained spectral measurements of H2 S(1), CH4, C2H2, C2H4 and C2H6 emission of Jupiter's high latitudes using TEXES on Gemini-North, which has a 8-metre primary aperture. This rare opportunity combines the superior spectral resolving power of TEXES and the high spatial resolution provided by Gemini-North's 8-metre aperture. We will perform a retrieval analyses to determine the 3D distributions of temperature, C2H2, C2H4 and C2H6. The morphology will be compared with near-contemporaneous measurements of H3+ emission from</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730051495&hterms=nike&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dnike','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730051495&hterms=nike&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dnike"><span>An example of anticorrelation of <span class="hlt">auroral</span> particles and electric fields.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maynard, N. C.; Bahnsen, A.; Christophersen, P.; Lundin, R.; Egeland, A.</p> <p>1973-01-01</p> <p>The question of whether correlation or anticorrelation should occur is complex and depends on many factors, e.g., the internal impedance of the source; the Pedersen conductivity, which in turn is dependent on the incident energy of the precipitated particles; whether space charge can build up; and the magnitude of the incoming flux. Data are presented from a case in which an anticorrelation between <span class="hlt">auroral</span> particles and electric fields is especially striking. The data were obtained from a Nike Tomahawk launched from the Norwegian rocket range at Andoya. The experiments carried are described briefly. The data support the anticorrelation model as one mechanism that can affect the electric field strength in <span class="hlt">auroral</span> regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050110125&hterms=comparative&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcomparative','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050110125&hterms=comparative&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcomparative"><span>Aurora and Non-<span class="hlt">Auroral</span> X-ray Emissions from Jupiter: A Comparative View</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bhardwal, Anil; Elsner, Ron; Gladstone, Randy; Waite, Hunter, Jr.; Lugaz, Noe; Cravens, Tom; Branduardi-Raymont, Graziella; Ramsay, Gavin; Soria, Rob; Ford, Peter</p> <p>2004-01-01</p> <p>Jovian X-rays can be broadly classified into two categories: (1) <span class="hlt">auroral</span> emission, which is confined to high-latitudes (approximately greater than 60 deg.) at both polar regions, and (2) dayglow emission, which originates from the sunlit low-latitude (approximately less than 50 deg.) regions of the disk (hereafter called disk emissions). Recent X-ray observations of Jupiter by chandra and XMM-Newton have shown that these two types of X-ray emission from Jupiter have different morphological, temporal, and spectral characteristics. In particular: 1) contrary to the <span class="hlt">auroral</span> X-rays, which are concentrated in a spot in the north and in a band that runs half-way across the planet in the south, the low-latitude X-ray disk is almost uniform; 2) unlike the approximately 40 plus or minus 20-min periodic oscillations seen in the <span class="hlt">auroral</span> X-ray emissions, the disk emissions do not show any periodic oscillations; 3) the disk emission is harder and extends to higher energies than the <span class="hlt">auroral</span> spectrum; and 4) the disk X-ray emission show time variability similar to that seen in solar X-rays. These differences and features imply that the processes producing X-rays are different at these two latitude regions on Jupiter. We will present the details of these and other features that suggest the differences between these two classes of X-ray emissions from Jupiter, and discuss the current scenario of the production mechanism of them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM31A2619N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM31A2619N"><span>Superposed epoch analysis of O+ <span class="hlt">auroral</span> outflow during sawtooth events and substorms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nowrouzi, N.; Kistler, L. M.; Lund, E. J.; Cai, X.</p> <p>2017-12-01</p> <p>Sawtooth events are repeated injection of energetic particles at geosynchronous orbit. Studies have shown that 94% of sawtooth events occurred during magnetic storm times. The main factor that causes a sawtooth event is still an open question. Simulations have suggested that heavy ions like O+ may play a role in triggering the injections. One of the sources of the O+ in the Earth's magnetosphere is the nightside aurora. O+ ions coming from the nightside <span class="hlt">auroral</span> region have direct access to the near-earth magnetotail. A model (Brambles et al. 2013) for interplanetary coronal mass ejection driven sawtooth events found that nightside O+ outflow caused the subsequent teeth of the sawtooth event through a feedback mechanism. This work is a superposed epoch analysis to test whether the observed <span class="hlt">auroral</span> outflow supports this model. Using FAST spacecraft data from 1997-2007, we examine the <span class="hlt">auroral</span> O+ outflow as a function of time relative to an injection onset. Then we determine whether the profile of outflow flux of O+ during sawtooth events is different from the outflow observed during isolated substorms. The <span class="hlt">auroral</span> region boundaries are estimated using the method of (Andersson et al. 2004). Subsequently the O+ outflow flux inside these boundaries are calculated and binned as a function of superposed epoch time for substorms and sawtooth "teeth". In this way, we will determine if sawtooth events do in fact have greater O+ outflow, and if that outflow is predominantly from the nightside, as suggested by the model results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006EP%26S...58.1107I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006EP%26S...58.1107I"><span>Preliminary results of rocket attitude and <span class="hlt">auroral</span> green line emission rate in the DELTA campaign</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iwagami, Naomoto; Komada, Sayaka; Takahashi, Takao</p> <p>2006-09-01</p> <p>The attitude of a sounding rocket launched in the DELTA (Dynamics and Energetics of the Lower Thermosphere in Aurora) campaign was determined with IR horizon sensors and geomagnetic sensors. Since the payload was separated into two portions, two sets of attitude sensors were needed. A new IR sensor was developed for the present experiment, and found the zenith-angle of the spin-axis of the rocket with an accuracy of 2°. By combining information obtained by both type of sensors, the absolute attitudes were determined. The <span class="hlt">auroral</span> green line emission rate was measured by a photometer on board the same rocket launched under active <span class="hlt">auroral</span> conditions, and the energy flux of the <span class="hlt">auroral</span> particle precipitation was estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920068571&hterms=polar+bear&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpolar%2Bbear','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920068571&hterms=polar+bear&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpolar%2Bbear"><span>Determining the source region of <span class="hlt">auroral</span> emissions in the prenoon oval using coordinated Polar BEAR UV-imaging and DMSP particle measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Newell, Patrick T.; Meng, CHING-I.; Huffman, Robert E.</p> <p>1992-01-01</p> <p>The Polar Beacon Experiment and <span class="hlt">Auroral</span> Research (Polar BEAR) satellite included the capability for imaging the dayside <span class="hlt">auroral</span> oval in full sunlight at several wavelengths. Particle observations from the DMSP F7 satellite during dayside <span class="hlt">auroral</span> oval crossings are compared with approximately simultaneous Polar BEAR 1356-A images to determine the magnetospheric source region of the dayside <span class="hlt">auroral</span> oval. The source region is determined from the DMSP particle data, according to recent work concerning the classification and identification of precipitation source regions. The close DMSP/Polar BEAR coincidences all occur when the former satellite is located between 0945 and 1000 MLT. Instances of <span class="hlt">auroral</span> arcs mapping to each of several different regions, including the boundary plasma sheet, the low-latitude boundary layer, and the plasma mantle were found. It was determined that about half the time the most prominent <span class="hlt">auroral</span> arcs are located at the interfaces between distinct plasma regions, at least at the local time studied here.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMSM51A0280H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMSM51A0280H"><span>Temporal Development of <span class="hlt">Auroral</span> Acceleration Potentials: High-Altitude Evolutionary Sequences, Drivers and Consequences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hull, A. J.; Wilber, M.; Chaston, C.; Bonnell, J.; Mozer, F.; McFadden, J.; Goldstein, M.; Fillingim, M.</p> <p>2007-12-01</p> <p>The region above the <span class="hlt">auroral</span> acceleration region is an integral part of the <span class="hlt">auroral</span> zone electrodynamic system. At these altitudes (≥ 3 Re) we find the source plasma and fields that determine acceleration processes occurring at lower altitudes, which play a key role in the transport of mass and energy into the ionosphere. Dynamic changes in these high-altitude regions can affect and/or control lower-altitude acceleration processes according to how field-aligned currents and specific plasma sources form and decay and how they are spatially distributed, and through magnetic configuration changes deeper in the magnetotail. Though much progress has been made, the time development and consequential effects of the high-altitude plasma and fields are still not fully understood. We present Cluster multi-point observations at key instances within and above the acceleration region (> 3 RE) of evolving <span class="hlt">auroral</span> arc current systems. Results are presented from events occurring under different conditions, such as magnetospheric activity, associations with density depletions or gradients, and Alfvenic turbulence. A preliminary survey, primarily at or near the plasma sheet boundary, indicates quasi- static up-down current pair systems are at times associated with density depletions and other instances occur in association with density gradients. The data suggest that such quasi-static current systems may be evolving from structured Alfvenic current systems. We will discuss the temporal development of <span class="hlt">auroral</span> acceleration potentials, plasma and currents, including quasi-static system formation from turbulent systems of structured Alfvenic field-aligned currents, density depletion and constituent reorganization of the source and ionospheric plasma that transpire in such systems. Of particular emphasis is how temporal changes in magnetospheric source plasma and fields affect the development of <span class="hlt">auroral</span> acceleration potentials at lower altitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820040361&hterms=barium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbarium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820040361&hterms=barium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbarium"><span>The electric field structure of <span class="hlt">auroral</span> arcs as determined from barium plasma injection experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wescott, E. M.</p> <p>1981-01-01</p> <p>Barium plasma injection experiments have revealed a number of features of electric fields in and near <span class="hlt">auroral</span> forms extending from a few hundred to many thousands of km in altitude. There is evidence for V-type potential structures over some auroras, but not in others. For some <span class="hlt">auroral</span> arcs, large E fields are found at ionospheric altitudes outside the arc but the E field inside the arc is near zero. In a few other auroras, most recently one investigated in an experiment conducted from Poker Flat on March 22, 1980, large, rapidly fluctuating E fields were detected by barium plasma near 600 km altitude. These E fields suggest that the motion of <span class="hlt">auroral</span> rays can be an effect of low-altitude electric fields, or that V-type potential structures may be found at low altitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PASJ...69L...1C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PASJ...69L...1C"><span>Unusual rainbows as <span class="hlt">auroral</span> candidates: Another point of view</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carrasco, Víctor M. S.; Trigo, Ricardo M.; Vaquero, José M.</p> <p>2017-04-01</p> <p>Several <span class="hlt">auroral</span> events that occurred in the past have not been cataloged as such due to the fact that they were described in the historical sources with different terminologies. Hayakawa et al. (2016, PASJ, 68, 33) have reviewed historical Oriental chronicles and proposed the terms “unusual rainbow” and “white rainbow” as candidates for auroras. In this work, we present three events that took place in the 18th century in two different settings (the Iberian Peninsula and Brazil) that were originally described with similar definitions or wording to that used by the Oriental chronicles, despite the inherent differences in terms associated with Oriental and Latin languages. We show that these terms are indeed applicable to the three case studies from Europe and South America. Thus, the <span class="hlt">auroral</span> catalogs available can be extended to Occidental sources using this new terminology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970040338&hterms=estado&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Destado','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970040338&hterms=estado&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Destado"><span>Excitation of Plasma Waves in Aurora by <span class="hlt">Electron</span> Beams</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>daSilva, C. E.; Vinas, A. F.; deAssis, A. S.; deAzevedo, C. A.</p> <p>1996-01-01</p> <p>In this paper, we study numerically the excitation of plasma waves by <span class="hlt">electron</span> beams, in the <span class="hlt">auroral</span> region above 2000 km of altitude. We have solved the fully kinetic dispersion relation, using numerical method and found the real frequency and the growth rate of the plasma wave modes. We have examined the instability properties of low-frequency waves such as the Electromagnetic Ion Cyclotron (EMIC) wave as well as Lower-Hybrid (LH) wave in the range of high-frequency. In all cases, the source of free energy are <span class="hlt">electron</span> beams propagating parallel to the geomagnetic field. We present some features of the growth rate modes, when the cold plasma parameters are changed, such as background <span class="hlt">electrons</span> and ions species (H(+) and O(+)) temperature, density or the <span class="hlt">electron</span> beam density and/or drift velocity. These results can be used in a test-particle simulation code, to investigate the ion acceleration and their implication in the <span class="hlt">auroral</span> acceleration processes, by wave-particle interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930071342&hterms=horses&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dhorses','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930071342&hterms=horses&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dhorses"><span>Dynamics Explorer measurements of particles, fields, and plasma drifts over a horse-collar <span class="hlt">auroral</span> pattern</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sharber, J. R.; Hones, E. W., Jr.; Heelis, R. A.; Craven, J. D.; Frank, L. A.; Maynard, N. C.; Slavin, J. A.; Birn, J.</p> <p>1992-01-01</p> <p>As shown from ground-based measurements and satellite-borne imagers, one type of global <span class="hlt">auroral</span> pattern characteristic of quiet (usually northward IMF) intervals is that of a contracted but thickened emission region of a pattern referred to as 'horse-collar' aurora (Hones et al., 1989). In this report we use the Dynamics Explorer data set to examine a case in which this horse-collar pattern was observed by the DE-1 <span class="hlt">auroral</span> imager, while at the same time DE-2, at lower altitude, measured precipitating particles, electric and magnetic fields, and plasma drifts. Our analysis shows that, in general, there is close agreement between the optical signatures and the particle precipitation patterns. In many instances, over scales ranging from tens to a few hundred kilometers, <span class="hlt">electron</span> precipitation features and upward field-aligned currents are observed at locations where the plasma flow gradients indicate negative V-average x E. The particle, plasma, and field measurements made along the satellite track and the 2D perspective of the imager provide a means of determining the configuration of convective flows in the high-latitude ionosphere during this interval of northward IMF. Recent mapping studies are used to relate the low-altitude observations to possible magnetospheric source regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840017135','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840017135"><span><span class="hlt">Auroral</span> kilometric radiation: Wave modes, harmonic and source region <span class="hlt">electron</span> density structures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benson, R. F.</p> <p>1984-01-01</p> <p>A change from extraordinary (X) mode to ordinary (0) mode dominance is observed in the <span class="hlt">auroral</span> kilometric radiation (AKR) detected on ISIS 1 topside sounder ionograms as the source region plasma to gyrofrequency ratio fN/fH varies from 0.1 to 1.3. The X and 0 mode AKR, Z (the slow branch of the X mode) and whistler (W) mode are also observed. The Z mode is typically slightly less intense than the 0-mode. Thw W-mode is confined to frequencies less than fH/2, suggesting that it is the result of field aligned ducted signals reaching the satellite from a source at lower altitudes. Harmonic AKR bands are commonly observed and the 2nd harmonic appears to be due to propagating signals. The deduced (fN/fH) at the bottom of the AKR source region is always less than 0.4 and is typically less than 0.2 during the generation of X-mode AKR, but approaches 0.9 for 0-mode AKR. No large density enhancements were observed within AKR source region density cavities. It is suggested that the observed INTENSE AKR IS cyclotron X-mode radiation rather than plasma frequency 0-mode radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSA34A..03C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSA34A..03C"><span>Comparisons of Simulated and Observed Sub-<span class="hlt">Auroral</span> Polarization Stream (SAPS) during the 17 March 2013 Storm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, M.; Lemon, C.; Sazykin, S. Y.; Wolf, R.; Anderson, P. C.</p> <p>2016-12-01</p> <p>Sub-<span class="hlt">Auroral</span> Polarization Streams (SAPS), characterized by large subauroral E x B velocities that span from dusk to the early morning sector for high magnetic activity, result from strong magnetosphere-ionosphere coupling. We investigate how <span class="hlt">electron</span> and ion precipitation and the ionospheric conductance affect the simulated development of the SAPS electric field for the 17 March 2013 storm. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the SAPS. We use parameterized rates of whistler-generated <span class="hlt">electron</span> pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. Ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. The <span class="hlt">electron</span> and proton contributions to the <span class="hlt">auroral</span> conductance in the RCM-E are calculated using the empirical Robinson et al. [JGR, 1987] and Galand and Richmond [JGR, 2001] equations, respectively. The "background" ionospheric conductance is based on parameters from the International Reference Ionosphere [Bilitza and Reinisch, JASR, 2008] but modified to include the effect of specified ionospheric troughs. Parameterized simulations will aid in understanding the underlying physical process. We compare simulated precipitating particle energy flux and E x B velocities with DMSP observations where SAPS are observed during the 17 March 2013 storm. Analysis of discerpancies between the simulation results and data will aid us in assessing needed improvements in the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011EP%26S...63...47G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011EP%26S...63...47G"><span>Lunar ionosphere exploration method using <span class="hlt">auroral</span> kilometric radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goto, Yoshitaka; Fujimoto, Takamasa; Kasahara, Yoshiya; Kumamoto, Atsushi; Ono, Takayuki</p> <p>2011-01-01</p> <p>The evidence of a lunar ionosphere provided by radio occultation experiments performed by the Soviet spacecraft Luna 19 and 22 has been controversial for the past three decades because the observed large density is difficult to explain theoretically without magnetic shielding from the solar wind. The KAGUYA mission provided an opportunity to investigate the lunar ionosphere with another method. The natural plasma wave receiver (NPW) and waveform capture (WFC) instruments, which are subsystems of the lunar radar sounder (LRS) on board the lunar orbiter KAGUYA, frequently observe <span class="hlt">auroral</span> kilometric radiation (AKR) propagating from the Earth. The dynamic spectra of the AKR sometimes exhibit a clear interference pattern that is caused by phase differences between direct waves and waves reflected on a lunar surface or a lunar ionosphere if it exists. It was hypothesized that the <span class="hlt">electron</span> density profiles above the lunar surface could be evaluated by comparing the observed interference pattern with the theoretical interference patterns constructed from the profiles with ray tracing. This method provides a new approach to examining the lunar ionosphere that does not involve the conventional radio occultation technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1255852-energy-dependent-dynamics-kev-mev-electrons-inner-zone-outer-zone-slot-regions','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1255852-energy-dependent-dynamics-kev-mev-electrons-inner-zone-outer-zone-slot-regions"><span>Energy-dependent dynamics of <span class="hlt">keV</span> to MeV <span class="hlt">electrons</span> in the inner zone, outer zone, and slot regions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Reeves, Geoffrey D.; Friedel, Reiner H. W.; Larsen, Brian A.; ...</p> <p>2016-01-28</p> <p>Here, we present observations of the radiation belts from the Helium Oxygen Proton <span class="hlt">Electron</span> and Magnetic <span class="hlt">Electron</span> Ion Spectrometer particle detectors on the Van Allen Probes satellites that illustrate the energy dependence and L shell dependence of radiation belt enhancements and decays. We survey events in 2013 and analyze an event on 1 March in more detail. The observations show the following: (a) at all L shells, lower energy <span class="hlt">electrons</span> are enhanced more often than higher energies; (b) events that fill the slot region are more common at lower energies; (c) enhancements of <span class="hlt">electrons</span> in the inner zone are moremore » common at lower energies; and (d) even when events do not fully fill the slot region, enhancements at lower energies tend to extend to lower L shells than higher energies. During enhancement events the outer zone extends to lower L shells at lower energies while being confined to higher L shells at higher energies. The inner zone shows the opposite with an outer boundary at higher L shells for lower energies. Both boundaries are nearly straight in log(energy) versus L shell space. At energies below a few 100 <span class="hlt">keV</span>, radiation belt <span class="hlt">electron</span> penetration through the slot region into the inner zone is commonplace, but the number and frequency of “slot filling” events decreases with increasing energy. The inner zone is enhanced only at energies that penetrate through the slot. Energy- and L shell-dependent losses (that are consistent with whistler hiss interactions) return the belts to more quiescent conditions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26082026','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26082026"><span>Investigation of the effective atomic numbers of dosimetric materials for <span class="hlt">electrons</span>, protons and alpha particles using a direct method in the energy region 10 <span class="hlt">keV</span>-1 GeV: a comparative study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kurudirek, Murat; Aksakal, Oğuz; Akkuş, Tuba</p> <p>2015-11-01</p> <p>A direct method has been used for the first time, to compute effective atomic numbers (Z eff) of water, air, human tissues, and some organic and inorganic compounds, for total <span class="hlt">electron</span> proton and alpha particle interaction in the energy region 10 <span class="hlt">keV</span>-1 GeV. The obtained values for Z eff were then compared to those obtained using an interpolation procedure. In general, good agreement has been observed for <span class="hlt">electrons</span>, and the difference (%) in Z eff between the results of the direct and the interpolation method was found to be <10 % for all materials, in the energy range from 10 <span class="hlt">keV</span> to 1 MeV. More specifically, results of the two methods were found to agree well (Dif. <10 %) for air, calcium fluoride, kapton polyimide film, paraffin wax and plastic scintillator in the entire energy region with respect to the total <span class="hlt">electron</span> interaction. On the other hand, values for Z eff calculated using both methods for protons and alpha particles generally agree with each other in the high-energy region above 10 MeV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...10527531F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...10527531F"><span>Pulsating midmorning <span class="hlt">auroral</span> arcs, filamentation of a mixing region in a flank boundary layer, and ULF waves observed during a Polar-Svalbard conjunction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farrugia, C. J.; Sandholt, P. E.; Maynard, N. C.; Burke, W. J.; Scudder, J. D.; Ober, D. M.; Moen, J.; Russell, C. T.</p> <p>2000-12-01</p> <p>Magnetically conjugate observations by the HYDRA and the Magnetic Field Experiment instruments on Polar, meridian-scanning photometers and all-sky imagers at Ny-Ålesund, and International Monitor for <span class="hlt">Auroral</span> Geomagnetic Effects (IMAGE) magnetometers on November 30, 1997, illustrate aspects of magnetosphere-ionosphere coupling at 0900-1000 magnetic local times (MLT) and 70°-80° magnetic latitudes and their dependence on interplanetary parameters. Initially, Polar crossed a boundary layer on closed field lines where magnetospheric and magnetosheath plasmas are mixed. This region contains filaments where magnetospheric <span class="hlt">electron</span> and ion fluxes are enhanced. These filaments are associated with field-aligned current structures embedded within the large-scale region 1 (R1) current. Ground <span class="hlt">auroral</span> imagery document the presence at this time of discrete, east-west aligned arcs, which are in one-to-one correspondence with the filaments. Temporal variations present in these <span class="hlt">auroral</span> arcs correlate with Pc 5 pulsations and are probably related to modulations in the interplanetary electric field. The <span class="hlt">auroral</span> observations indicate that the filamented mixing region persisted for many tens of minutes, suggesting a spatial structuring. The data suggest further that the filamented, mixing region is an important source of the R1 current and the associated midmorning arcs. When the interplanetary magnetic field (IMF) turned strongly north, Polar had entered the dayside extension of the central plasma sheet/region 2 current system where it and the underlying ground magnetometers recorded a clear field line resonance of frequency ~2.4 mHz (Pc 5 range). The source of these oscillations is most likely the Kelvin-Helmholtz instability. Subsequent to the IMF northward turning, the multiple arcs were replaced by a single <span class="hlt">auroral</span> form to the north of Ny-Ålesund (at 1000 MLT) in the vicinity of the westward edge of the cusp. ULF pulsation activity changed to the Pc 3-4 range in the regime of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMSM11A1590T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMSM11A1590T"><span>The sub-<span class="hlt">auroral</span> electric field as observed by DMSP and the new SuperDARN mid-latitude radars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talaat, E. R.; Sotirelis, T.; Hairston, M. R.; Ruohoniemi, J. M.; Greenwald, R. A.; Lester, M.</p> <p>2008-12-01</p> <p>In this paper we present analyses of the sub-<span class="hlt">auroral</span> electric field environment as observed from both space and ground. We discuss the dependency of the configuration and strength of the sub-<span class="hlt">auroral</span> electric field on IMF and geomagnetic activity, longitudinal, seasonal, and solar cycle variability. Primarily, e use ~20 years of electric field measurement dataset derived from the suite of DMSP ion drift meters. A major component of our analysis is correctly specifying the aurora boundary, as the behavior and magnitude of these fields will be drastically different away from the high-conductance <span class="hlt">auroral</span> oval. As such, we use the coincident particle flux measurements from the DMSP SSJ4 monitors. We also present the solar minimum observations of the sub-<span class="hlt">auroral</span> flow newly available from the mid-latitude SuperDARN radars at Wallops and Blackstone in Virginia. Preliminary comparisons between these flows and the DMSP climatology are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170006548&hterms=tourism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtourism','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170006548&hterms=tourism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtourism"><span>Space Weather Products and Tools Used in <span class="hlt">Auroral</span> Monitoring and Forecasting at CCMC/SWRC</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zheng, Yihua; Rastaetter, Lutz</p> <p>2015-01-01</p> <p>Key points discussed in this chapter are (1) the importance of aurora research to scientific advances and space weather applications, (2) space weather products at CCMC that are relevant to aurora monitoring and forecasting, and (3) the need for more effort from the whole community to achieve a better and long-lead-time forecast of <span class="hlt">auroral</span> activity. Aurora, as manifestations of solar wind-magnetosphere-ionosphere coupling that occurs in a region of space that is relatively easy to access for sounding rockets, satellites, and other types of observational platforms, serves as a natural laboratory for studying the underlying physics of the complex system. From a space weather application perspective, auroras can cause surface charging of technological assets passing through the region, result in scintillation effects affecting communication and navigation, and cause radar cluttering that hinders military and civilian applications. Indirectly, an aurora and its currents can induce geomagnetically induced currents (GIC) on the ground, which poses major concerns for the wellbeing and operation of power grids, particularly during periods of intense geomagnetic activity. In addition, accurate <span class="hlt">auroral</span> forecasting is desired for <span class="hlt">auroral</span> tourism. In this chapter, we first review some of the existing <span class="hlt">auroral</span> models and discuss past validation efforts. Such efforts are crucial in transitioning a model(s) from research to operations and for further model improvement and development that also benefits scientific endeavors. Then we will focus on products and tools that are used for <span class="hlt">auroral</span> monitoring and forecasting at the Space Weather Research Center (SWRC). As part of the CCMC (Community Coordinated Modeling Center), SWRC has been providing space weather services since 2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA405592','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA405592"><span>Characterization of the <span class="hlt">Auroral</span> Electrojet and the Ambient and Modified D Region for HAARP Using Long-Path VLF Diagnostics</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2001-03-15</p> <p>order to characterize the <span class="hlt">auroral</span> electrojet and the ambient and modified D-region directly above and near the HAARP (High Frequency Active <span class="hlt">Auroral</span>...near the HAARP facility and along the west coast of Alaska. In addition in order to characterize the <span class="hlt">auroral</span> electrojet on a continental scale and to...United States and Canada. Data from the complete array of D-region diagnostic systems was acquired during a number of Fall and Spring HAARP campaigns</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........65H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........65H"><span>Alfven Waves Underlying Ionospheric Destabilization: Ground-Based Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirsch, Michael</p> <p></p> <p>During geomagnetic storms, terawatts of power in the million mile-per-hour solar wind pierce the Earth's magnetosphere. Geomagnetic storms and substorms create transverse magnetic waves known as Alfven waves. In the <span class="hlt">auroral</span> acceleration region, Alfven waves accelerate <span class="hlt">electrons</span> up to one-tenth the speed of light via wave-particle interactions. These inertial Alfven wave (IAW) accelerated <span class="hlt">electrons</span> are imbued with sub-100 meter structure perpendicular to geomagnetic field B. The IAW electric field parallel to B accelerates <span class="hlt">electrons</span> up to about 10 <span class="hlt">keV</span> along B. The IAW dispersion relation quantifies the precipitating <span class="hlt">electron</span> striation observed with high-speed cameras as spatiotemporally dynamic fine structured aurora. A network of tightly synchronized tomographic <span class="hlt">auroral</span> observatories using model based iterative reconstruction (MBIR) techniques were developed in this dissertation. The TRANSCAR <span class="hlt">electron</span> penetration model creates a basis set of monoenergetic <span class="hlt">electron</span> beam eigenprofiles of <span class="hlt">auroral</span> volume emission rate for the given location and ionospheric conditions. Each eigenprofile consists of nearly 200 broadband line spectra modulated by atmospheric attenuation, bandstop filter and imager quantum efficiency. The L-BFGS-B minimization routine combined with sub-pixel registered <span class="hlt">electron</span> multiplying CCD video stream at order 10 ms cadence yields estimates of <span class="hlt">electron</span> differential number flux at the top of the ionosphere. Our automatic data curation algorithm reduces one terabyte/camera/day into accurate MBIR-processed estimates of IAW-driven <span class="hlt">electron</span> precipitation microstructure. This computer vision structured <span class="hlt">auroral</span> discrimination algorithm was developed using a multiscale dual-camera system observing a 175 km and 14 km swath of sky simultaneously. This collective behavior algorithm exploits the "swarm" behavior of aurora, detectable even as video SNR approaches zero. A modified version of the algorithm is applied to topside ionospheric radar at Mars and</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170003498&hterms=Citizen+science&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCitizen%2Bscience','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170003498&hterms=Citizen+science&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCitizen%2Bscience"><span>Using Citizen Science Reports to Define the Equatorial Extent of <span class="hlt">Auroral</span> Visibility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Case, N. A.; MacDonald, E. A.; Viereck, R.</p> <p>2016-01-01</p> <p>An aurora may often be viewed hundreds of kilometers equatorward of the <span class="hlt">auroral</span> oval owing to its altitude. As such, the NOAA Space Weather Prediction Center (SWPC) Aurora Forecast product provides a "view line" to demonstrate the equatorial extent of <span class="hlt">auroral</span> visibility, assuming that it is sufficiently bright and high in altitude. The view line in the SWPC product is based upon the latitude of the brightest aurora, for each hemisphere, as specified by the real-time oval variation, assessment, tracking, intensity, and online nowcasting (OVATION) Prime (2010) aurora precipitation model. In this study, we utilize nearly 500 citizen science <span class="hlt">auroral</span> reports to compare with the view line provided by an updated SWPC aurora forecast product using <span class="hlt">auroral</span> precipitation data from OVATION Prime (2013). The citizen science observations were recorded during March and April 2015 using the Aurorasaurus platform and cover one large geomagnetic storm and several smaller events. We find that this updated SWPC view line is conservative in its estimate and that the aurora is often viewable further equatorward than Is indicated by the forecast. By using the citizen reports to modify the scaling parameters used to link the OVATION Prime (2013) model to the view line, we produce a new view line estimate that more accurately represents the equatorial extent of visible aurora. An OVATION Prime (2013) energy flux-based equatorial boundary view line is also developed and is found to provide the best overall agreement with the citizen science reports, with an accuracy of 91 percent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100024498','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100024498"><span>Development of a Geomagnetic Storm Correction to the International Reference Ionosphere E-Region <span class="hlt">Electron</span> Densities Using TIMED/SABER Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mertens, C. J.; Xu, X.; Fernandez, J. R.; Bilitza, D.; Russell, J. M., III; Mlynczak, M. G.</p> <p>2009-01-01</p> <p><span class="hlt">Auroral</span> infrared emission observed from the TIMED/SABER broadband 4.3 micron channel is used to develop an empirical geomagnetic storm correction to the International Reference Ionosphere (IRI) E-region <span class="hlt">electron</span> densities. The observation-based proxy used to develop the storm model is SABER-derived NO+(v) 4.3 micron volume emission rates (VER). A correction factor is defined as the ratio of storm-time NO+(v) 4.3 micron VER to a quiet-time climatological averaged NO+(v) 4.3 micron VER, which is linearly fit to available geomagnetic activity indices. The initial version of the E-region storm model, called STORM-E, is most applicable within the <span class="hlt">auroral</span> oval region. The STORM-E predictions of E-region <span class="hlt">electron</span> densities are compared to incoherent scatter radar <span class="hlt">electron</span> density measurements during the Halloween 2003 storm events. Future STORM-E updates will extend the model outside the <span class="hlt">auroral</span> oval.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4648G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4648G"><span>A Statistical Survey of the 630.0-nm Optical Signature of Periodic <span class="hlt">Auroral</span> Arcs Resulting From Magnetospheric Field Line Resonances</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gillies, D. Megan; Knudsen, David; Rankin, Robert; Milan, Stephen; Donovan, Eric</p> <p>2018-05-01</p> <p>Advances in networks of ground-based optical instrumentation have enabled us to identify over 400 examples of <span class="hlt">auroral</span> arcs with an infrequently observed, temporally periodic <span class="hlt">auroral</span> morphology. This study focuses on these arcs observed via the 630-nm ("redline") <span class="hlt">auroral</span> emission wavelength and connects them to global magnetospheric wave modes known as field line resonances (FLRs). We show that optical redline FLR <span class="hlt">auroral</span> arcs occur most frequently near 20 and 4 magnetic local time, in contrast to nonperiodic redline arcs, which occur most frequently near midnight. We find that this periodic type of <span class="hlt">auroral</span> arc is rare, occurring in approximately 5% of redline aurora observed by the Redline Emission Geospace Observatory all-sky imagers. We also show Swarm satellite observations of two separate instances of 630-nm FLR arcs with strong upward field-aligned currents of the order of 3-6 μA/m2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JPhCS..71a2011C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JPhCS..71a2011C"><span>Non-equilibrium calculations of atmospheric processes initiated by <span class="hlt">electron</span> impact.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Campbell, L.; Brunger, M. J.</p> <p>2007-05-01</p> <p><span class="hlt">Electron</span> impact in the atmosphere produces ionisation, dissociation, <span class="hlt">electronic</span> excitation and vibrational excitation of atoms and molecules. The products can then take part in chemical reactions, recombination with <span class="hlt">electrons</span>, or radiative or collisional deactivation. While most such processes are fast, some longer--lived species do not reach equilibrium. The <span class="hlt">electron</span> source (photoelectrons or <span class="hlt">auroral</span> <span class="hlt">electrons</span>) also varies over time and longer-lived species can move substantially in altitude by molecular, ambipolar or eddy diffusion. Hence non-equilibrium calculations are required in some circumstances. Such time-step calculations need to have sufficiently short steps so that the fastest processes are still calculated correctly, but this can lead to computation times that are too large. Hence techniques to allow for longer time steps by incorporating equilibrium calculations are described. Examples are given for results of atmospheric non-equilibrium calculations, including the populations of the vibrational levels of ground state N2, the <span class="hlt">electron</span> density and its dependence on vibrationally excited N2, predictions of nitric oxide density, and detailed processes during short duration <span class="hlt">auroral</span> events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950057064&hterms=recurrence+sequences&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Drecurrence%2Bsequences','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950057064&hterms=recurrence+sequences&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Drecurrence%2Bsequences"><span>Cusp/cleft <span class="hlt">auroral</span> activity in relation to solar wind dynamic pressure, interplanetary magnetic field B(sub z) and B(sub y)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sandholt, P. E.; Farrugia, C. J.; Burlaga, L. F.; Holtet, J. A.; Moen, J.; Lybekk, B.; Jacobsen, B.; Opsvik, D.; Egeland, A.; Lepping, R.</p> <p>1994-01-01</p> <p>Continuous optical observations of cusp/cleft <span class="hlt">auroral</span> activities within approximately equal to 09-15 MLT and 70-76 deg magnetic latitude are studied in relation to changes in solar wind dynamic pressure and interplanetary magnetic field (IMF) variability. The observed latitudinal movements of the cusp/cleft aurora in response to IMF B(sub z) changes may be explained as an effect of a variable magnetic field intensity in the outer dayside magnetosphere associated with the changing intensity of region 1 field-aligned currents and associated closure currents. Ground magnetic signatures related to such currents were observed in the present case (January 10, 1993). Strong, isolated enhancements in solar wind dynamic pressure (Delta p/p is greater than or equal to 0.5) gave rise to equatorward shifts of the cusp/cleft aurora, characteristic <span class="hlt">auroral</span> transients, and distinct ground magnetic signatures of enhanced convection at cleft latitudes. A sequence of <span class="hlt">auroral</span> events of approximately equal to 5-10 min recurrence time, moving eastward along the poleward boundary of the persistent cusp/cleft aurora in the approximately equal to 10-14 MLT sector, during negative IMF B(sub z) and B(sub y) conditions, were found to be correlated with brief pulses in solar wind dynamic pressure (0.1 is less than Delta p/p is less than 0.5). Simultaneous photometer observations from Ny Alesund, Svalbard, and Danmarkshavn, Greenland, show that the events often appeared on the prenoon side (approximately equal to 10-12 MLT), before moving into the postnoon sector in the case we study here, when IMF B(sub y) is less than 0. In other cases, similar <span class="hlt">auroral</span> event sequences have been observed to move westward in the prenoon sector, during intervals of positive B(sub y). Thus a strong prenoon/postnoon asymmetry of event occurence and motion pattern related to the IMF B(sub y) polarity is observed. We find that this category of <span class="hlt">auroral</span> event sequence is stimulated bursts of <span class="hlt">electron</span> precipitation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SpWea..13...16G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SpWea..13...16G"><span>Nowcast model for low-energy <span class="hlt">electrons</span> in the inner magnetosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ganushkina, N. Yu.; Amariutei, O. A.; Welling, D.; Heynderickx, D.</p> <p>2015-01-01</p> <p>We present the nowcast model for low-energy (<200 <span class="hlt">keV</span>) <span class="hlt">electrons</span> in the inner magnetosphere, which is the version of the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) for <span class="hlt">electrons</span>. Low-energy <span class="hlt">electron</span> fluxes are very important to specify when hazardous satellite surface-charging phenomena are considered. The presented model provides the low-energy <span class="hlt">electron</span> flux at all L shells and at all satellite orbits, when necessary. The model is driven by the real-time solar wind and interplanetary magnetic field (IMF) parameters with 1 h time shift for propagation to the Earth's magnetopause and by the real time Dst index. Real-time geostationary GOES 13 or GOES 15 (whenever each is available) data on <span class="hlt">electron</span> fluxes in three energies, such as 40 <span class="hlt">keV</span>, 75 <span class="hlt">keV</span>, and 150 <span class="hlt">keV</span>, are used for comparison and validation of IMPTAM running online. On average, the model provides quite reasonable agreement with the data; the basic level of the observed fluxes is reproduced. The best agreement between the modeled and the observed fluxes are found for <100 <span class="hlt">keV</span> <span class="hlt">electrons</span>. At the same time, not all the peaks and dropouts in the observed <span class="hlt">electron</span> fluxes are reproduced. For 150 <span class="hlt">keV</span> <span class="hlt">electrons</span>, the modeled fluxes are often smaller than the observed ones by an order of magnitude. The normalized root-mean-square deviation is found to range from 0.015 to 0.0324. Though these metrics are buoyed by large standard deviations, owing to the dynamic nature of the fluxes, they demonstrate that IMPTAM, on average, predicts the observed fluxes satisfactorily. The computed binary event tables for predicting high flux values within each 1 h window reveal reasonable hit rates being 0.660-0.318 for flux thresholds of 5 ·104-2 ·105 cm-2 s-1 sr-1 <span class="hlt">keV</span>-1 for 40 <span class="hlt">keV</span> <span class="hlt">electrons</span>, 0.739-0.367 for flux thresholds of 3 ·104-1 ·105 cm-2 s-1 sr-1 <span class="hlt">keV</span>-1 for 75 <span class="hlt">keV</span> <span class="hlt">electrons</span>, and 0.485-0.438 for flux thresholds of 3 ·103-3.5 ·103 cm-2 s-1 sr-1 <span class="hlt">keV</span>-1 for 150 <span class="hlt">keV</span> <span class="hlt">electrons</span> but rather small Heidke</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM23A2473H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM23A2473H"><span>New Insights into <span class="hlt">Auroral</span> Particle Acceleration via Coordinated Optical-Radar Networks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirsch, M.</p> <p>2016-12-01</p> <p>The efficacy of instruments synthesized from heterogeneous sensor networks is increasingly being realized in fielded science observation systems. New insights into the finest spatio-temporal scales of ground-observable ionospheric physics are realized by coupling low-level data from fixed legacy instruments with mobile and portable sensors. In particular, turbulent ionospheric events give enhanced radar returns more than three orders of magnitude larger than typical incoherent plasma observations. Radar integration times for the Poker Flat Incoherent Scatter Radar (PFISR) can thereby be shrunk from order 100 second integration time down to order 100 millisecond integration time for the ion line. <span class="hlt">Auroral</span> optical observations with 20 millisecond cadence synchronized in absolute time with the radar help uncover plausible particle acceleration processes for the highly dynamic aurora often associated with Langmuir turbulence. Quantitative analysis of coherent radar returns combined with a physics-based model yielding optical volume emission rate profiles vs. differential number flux input of precipitating particles into the ionosphere yield plausibility estimates for a particular <span class="hlt">auroral</span> acceleration process type. Tabulated results from a survey of <span class="hlt">auroral</span> events where the Boston University High Speed <span class="hlt">Auroral</span> Tomography system operated simultaneously with PFISR are presented. Context is given to the narrow-field HiST observations by the Poker Flat Digital All-Sky Camera and THEMIS GBO ASI network. Recent advances in high-rate (order 100 millisecond) plasma line ISR observations (100x improvement in temporal resolution) will contribute to future coordinated observations. ISR beam pattern and pulse parameter configurations favorable for future coordinated optical-ISR experiments are proposed in light of recent research uncovering the criticality of aspect angle to ISR-observable physics. High-rate scientist-developed GPS TEC receivers are expected to contribute additional</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMSH51B1283B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMSH51B1283B"><span>Custom <span class="hlt">auroral</span> electrojet indices calculated by using MANGO value-added services</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bargatze, L. F.; Moore, W. B.; King, T. A.</p> <p>2009-12-01</p> <p>A set of computational routines called MANGO, Magnetogram Analysis for the Network of Geophysical Observatories, is utilized to calculate customized versions of the <span class="hlt">auroral</span> electrojet indices, AE, AL, and AU. MANGO is part of an effort to enhance data services available to users of the Heliophysics VxOs, specifically for the Virtual Magnetospheric Observatory (VMO). The MANGO value-added service package is composed of a set of IDL routines that decompose ground magnetic field observations to isolate secular, diurnal, and disturbance variations of magnetic field disturbance, station-by-station. Each MANGO subroutine has been written in modular fashion to allow "plug and play"-style flexibility and each has been designed to account for failure modes and noisy data so that the programs will run to completion producing as much derived data as possible. The capabilities of the MANGO service package will be demonstrated through their application to the study of <span class="hlt">auroral</span> electrojet current flow during magnetic substorms. Traditionally, the AE indices are calculated by using data from about twelve ground stations located at northern <span class="hlt">auroral</span> zone latitudes spread longitudinally around the world. Magnetogram data are corrected for secular variation prior to calculating the standard version of the indices but the data are not corrected for diurnal variations. A custom version of the AE indices will be created by using the MANGO routines including a step to subtract diurnal curves from the magnetic field data at each station. The custom AE indices provide more accurate measures of <span class="hlt">auroral</span> electrojet activity due to isolation of the sunstorm electrojet magnetic field signiture. The improvements in the accuracy of the custom AE indices over the tradition indices are largest during the northern hemisphere summer when the range of diurnal variation reaches its maximum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870045492&hterms=maxwell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dm.m%2Bmaxwell','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870045492&hterms=maxwell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dm.m%2Bmaxwell"><span>The minimum bandwidths of <span class="hlt">auroral</span> kilometric radiation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baumback, M. M.; Calvert, W.</p> <p>1987-01-01</p> <p>The bandwidths of the discrete spectral components of the <span class="hlt">auroral</span> kilometric radiation can sometimes be as narrow as 5 Hz. Since this would imply an apparent source thickness of substantially less than the wavelength, it is inconsistent with the previous explanation for such discrete components based simply upon vertical localization of a cyclotron source. Instead, such narrow bandwidths can only be explained by radio lasing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950048767&hterms=1575&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231575','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950048767&hterms=1575&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231575"><span>The determination of interplanetary magnetic field polarities around sector boundaries using E greater than 2 <span class="hlt">keV</span> <span class="hlt">electrons</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kahler, S.; Lin, R. P.</p> <p>1994-01-01</p> <p>The determination of the polarities of interplanetary magnetic fields (whether the field direction is outward from or inward toward the sun) has been based on a comparison of observed field directions with the nominal Parker spiral angle. These polarities can be mapped back to the solar source field polarities. This technique fails when field directions deviate substantially from the Parker angle or when fields are substantially kinked. We introduce a simple new technique to determine the polarities of interplanetary fields using E greater than 2 <span class="hlt">keV</span> interplanetary <span class="hlt">electrons</span> which stream along field lines away from the sun. Those <span class="hlt">electrons</span> usually show distinct unidirectional pitch-angle anisotropies either parallel or anti-parallel to the field. Since the <span class="hlt">electron</span> flow direction is known to be outward from the sun, the anisotropies parallel to the field indicate outward-pointing, positive-polarity fields, and those anti-parallel indicate inward-pointing, negative-polarity fields. We use data from the UC Berkeley <span class="hlt">electron</span> experiment on the International Sun Earth Explorer 3 (ISSE-3) spacecraft to compare the field polarities deduced from the <span class="hlt">electron</span> data, Pe (outward or inward), with the polarities inferred from field directions, Pd, around two sector boundaries in 1979. We show examples of large (greater than 100 deg) changes in azimuthal field direction Phi over short (less than 1 hr) time scales, some with and some without reversals in Pe. The latter cases indicate that such large directional changes can occur in unipolar structures. On the other hand, we found an example of a change in Pe during which the rotation in Phi was less than 30 deg, indicating polarity changes in nearly unidirectional structures. The field directions are poor guides to the polarities in these cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM53A..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM53A..01L"><span>Beyond the Electrostatic Ionosphere: Dynamic Coupling of the Magnetosphere and Ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lysak, R. L.; Song, Y.</p> <p>2017-12-01</p> <p>Many models of magnetospheric dynamics treat the ionosphere as a height-integrated slab in which the electric fields are electrostatic. However, in dynamic situations, the coupling between magnetosphere and ionosphere is achieved by the propagation of shear Alfvén waves. Hall effects lead to a coupling of shear Alfvén and fast mode waves, resulting in an inductive electric field and a compressional component of the magnetic field. It is in fact this compressional magnetic field that is largely responsible for the magnetic fields seen on the ground. A fully inductive ionosphere model is required to describe this situation. The shear Alfvén waves are affected by the strong gradient in the Alfvén speed above the ionosphere, setting up the ionospheric Alfvén resonator with wave periods in the 1-10 second range. These waves develop a parallel electric field on small scales that can produce a broadband acceleration of <span class="hlt">auroral</span> <span class="hlt">electrons</span>, which form the Alfvénic aurora. Since these <span class="hlt">electrons</span> are relatively low in energy (hundreds of eV to a few <span class="hlt">keV</span>), they produce <span class="hlt">auroral</span> emissions as well as ionization at higher altitudes. Therefore, they can produce localized columns of ionization that lead to structuring in the <span class="hlt">auroral</span> currents due to phase mixing or feedback interactions. This implies that the height-integrated description of the ionosphere is not appropriate in these situations. These considerations suggest that the Alfvénic aurora may, at least in some cases, act as a precursor to the development of a quasi-static <span class="hlt">auroral</span> arc. The acceleration of <span class="hlt">electrons</span> and ions produces a density cavity at higher altitudes that favors the formation of parallel electric fields. Furthermore, the precipitating <span class="hlt">electrons</span> will produce secondary and backscattered <span class="hlt">electrons</span> that provide a necessary population for the formation of double layers. These interactions strongly suggest that the simple electrostatic boundary condition often assumed is inadequate to describe <span class="hlt">auroral</span> arc</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010108000','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010108000"><span><span class="hlt">Auroral</span>, Polar Cap, and Polar Cusp Modeling and Data Analysis for the IMAGE Mission and LENA Instrument</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, Gordon R.</p> <p>2001-01-01</p> <p>One of the chief mysteries in the LENA perigee pass data is the lack of an apparent <span class="hlt">auroral</span> oval in the images. Another is that in some cases ENA are seen from any direction near the Earth regardless of the latitude of the spacecraft. These facts lead one to ask a fundamental question: Is the instrument responding to ENA primarily? One possible way to get out of the "ambiguity" of the data is to assume that at least part of the signal is produced by something other than ENA. The two main candidates for this "something else" are UV light and energetic charged particles. UV light could only effect the instrument when its fan shaped aperture points toward the source. The most intense of which will be the sun, with day glow being the second strongest and the <span class="hlt">auroral</span> zone, the third. We can rule out UV light as a prime source of counts in the perigee pass data for the following reasons: 1) The perigee pass signal is different in form and much stronger than the sun pulse signal seen just before or just after perigee; 2) There is no indication of the <span class="hlt">auroral</span> zone, which would produce at least two peaks in the counts versus spin phase curve; 3) Mike Colliers' analysis of the sun pulse signal shows that it varies with the flux of the solar wind and not with variations in the solar UV flux. Charge particles that enter the aperture of the instrument and produce counts would show up when the instrument looks in the direction from which they come. In all of the data I am analyzing voltages were being applied to the collimators so that most charged particles should have been excluded from the instrument but this effect could still show up where the flux of energetic particles is high enough. The most likely place would be in the <span class="hlt">auroral</span> zone where energetic <span class="hlt">electrons</span> and protons precipitate. If these particles are producing counts then they should be seen when the instrument looks in and near the zenith direction. In nearly all of the perigee passes the zenith direction is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70114648','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70114648"><span><span class="hlt">Auroral</span> omens of the American Civil War</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Love, Jeffrey J.</p> <p>2014-01-01</p> <p>Aurorae are a splendid night-time sight: coruscations of green, purple, and red fluorescent light in the form of gently wafting ribbons, billowing curtains, and flashing rays. Mostly seen at high latitudes, in the north aurorae are often called the northern lights or aurora borealis, and, in the south, the southern lights or aurora australis. The mystery of their cause has historically been the subject of wonder. The folklore and mythology of some far-northern civilizations attributed <span class="hlt">auroral</span> light to celestial deities. And, in ironic contrast with their heavenly beauty, unusual <span class="hlt">auroral</span> displays, such as those seen on rare occasions at lower southern latitudes, have sometimes been interpreted as portending unfavorable future events. Today we understand aurorae to be a visual manifestation of the dynamic conditions in the space environment surrounding the earth. Important direct evidence in support of this theory came on September 1, 1859. On that day, an English astronomer named Richard Carrington was situated at his telescope, which was pointed at the sun. While observing and sketching a large group of sunspots, he saw a solar flare—intense patches of white light that were superimposed upon the darker sunspot group and which were illuminated for about a minute. One day later, a magnetic storm was recorded at specially designed observatories in Europe, across Russia, and in India. By many measures, the amplitude of magnetic disturbance was the greatest ever recorded. In the United States, the effects of the Carrington storm could be seen as irregular backand-forth deflections of a few degrees in the magnetized needle of a compass. Rapid magnetic variation also induced electric fields in the earth’s conducting lithosphere, and interfered with the operation of telegraph systems. The Carrington magnetic storm, and an earlier storm that had occurred on August 28, 1859, caused spectacular displays of aurora borealis in the night-time sky over the entire United</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRA..117.2209Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRA..117.2209Y"><span>Numerical simulation for a vortex street near the poleward boundary of the nighttime <span class="hlt">auroral</span> oval</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, T.</p> <p>2012-02-01</p> <p>The formation of a vortex street is numerically studied as an aftermath of a transient (≈1 min) depression of the energy density of injected particles. It is basically assumed that the kinetic energies of <span class="hlt">auroral</span> particles are substantially provided by nonadiabatic acceleration in the tail current sheet. One of the causes of such energy density depression is an outward (away from the Earth) movement of the neutral line because in such situation, a particle passes the acceleration zone for a shorter time interval while it is inwardly transported in the current sheet. The numerical simulation shows that a long chain of many (≥5) vortices can be formed in the nighttime high-latitude <span class="hlt">auroral</span> oval as a result of the hybrid Kelvin-Helmholtz/Rayleigh-Taylor (KH/RT) instability. The main characteristics of long vortex chains in the simulation such as the short lifetime (≲2 min) and the correlation between wavelength, λ, and arc system width, A, compare well with those of the periodic <span class="hlt">auroral</span> distortions observed primarily in the high-latitude <span class="hlt">auroral</span> oval. Specifically, either λ-A relationship from simulation or observation shows a positive correlation between λ and A but with considerable dispersion in λ. Since <span class="hlt">auroral</span> vortices arising from the hybrid KH/RT instability are not accompanied by significant rotational motions, the magnetic shear instability caused by undulations in the field-aligned current (FAC) sheet could turn the vortices into spirals which wind or unwind in response to increase or decrease of FACs, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780048772&hterms=geomagnetism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeomagnetism','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780048772&hterms=geomagnetism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeomagnetism"><span>The Third General Scientific Assembly of the International Association of Geomagnetism and Aeronomy - Special sessions of <span class="hlt">auroral</span> processes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Russell, C. T.</p> <p>1978-01-01</p> <p>Methods of timing magnetic substorms, the rapid fluctuations of aurorae, electromagnetic and electrostatic instabilities observed on the field lines of aurorae, the <span class="hlt">auroral</span> microstructure, and the relationship of currents, electric field and particle precipitation to <span class="hlt">auroral</span> form are discussed. Attention is given to such topics as D-perturbations as an indicator of substorm onset, the role of the magnetotail in substorms, spectral information derived from imaging data on aurorae, terrestrial kilometric radiation, and the importance of the mirror force in self-consistent models of particle fluxes, currents and potentials on <span class="hlt">auroral</span> field lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850026431','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850026431"><span>Observations of solar flare photon energy spectra from 20 <span class="hlt">keV</span> to 7 MeV</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yoshimori, M.; Watanabe, H.; Nitta, N.</p> <p>1985-01-01</p> <p>Solar flare photon energy spectra in the 20 <span class="hlt">keV</span> to 7 MeV range are derived from the Apr. 1, Apr. 4, apr. 27 and May 13, 1981 flares. The flares were observed with a hard X-ray and a gamma-ray spectrometers on board the Hinotori satellite. The results show that the spectral shape varies from flare to flare and the spectra harden in energies above about 400 <span class="hlt">keV</span>. Effects of nuclear line emission on the continuum and of higher energy <span class="hlt">electron</span> bremsstrahlung are considered to explain the spectral hardening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990092494&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DMagnetic%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990092494&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DMagnetic%2Benergy"><span>Comparison of Dawn and Dusk Precipitating <span class="hlt">Electron</span> Energy Populations Shortly After the Initial Shock for the January 10th, 1997 Magnetic Cloud</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Spann, J.; Germany, G.; Swift, W.; Parks, G.; Brittnacher, M.; Elsen, R.</p> <p>1997-01-01</p> <p>The observed precipitating <span class="hlt">electron</span> energy between 0130 UT and 0400 UT of January 10 th, 1997, indicates that there is a more energetic precipitating <span class="hlt">electron</span> population that appears in the <span class="hlt">auroral</span> oval at 1800-2200 UT at 030) UT. This increase in energy occurs after the initial shock of the magnetic cloud reaches the Earth (0114 UT) and after faint but dynamic polar cap precipitation has been cleared out. The more energetic population is observed to remain rather constant in MLT through the onset of <span class="hlt">auroral</span> activity (0330 UT) and to the end of the Polar spacecraft apogee pass. Data from the Ultraviolet Imager LBH long and LBH short images are used to quantify the average energy of the precipitating <span class="hlt">auroral</span> <span class="hlt">electrons</span>. The Wind spacecraft located about 100 RE upstream monitored the IMF and plasma parameters during the passing of the cloud. The affects of oblique angle viewing are included in the analysis. Suggestions as to the source of this hot <span class="hlt">electron</span> population will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006peac.conf..305C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006peac.conf..305C"><span><span class="hlt">Electron</span> Driven Processes in Atmospheric Behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Campbell, L.; Brunger, M. J.; Teubner, P. J. O.</p> <p>2006-11-01</p> <p><span class="hlt">Electron</span> impact plays an important role in many atmospheric processes. Calculation of these is important for basic understanding, atmospheric modeling and remote sensing. Accurate atomic and molecular data, including <span class="hlt">electron</span> impact cross sections, are required for such calculations. Five <span class="hlt">electron</span>-driven processes are considered: <span class="hlt">auroral</span> and dayglow emissions, the reduction of atmospheric <span class="hlt">electron</span> density by vibrationally excited N2, NO production and infrared emission from NO. In most cases the predictions are compared with measurements. The dependence on experimental atomic and molecular data is also investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JPhB...51b5201B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JPhB...51b5201B"><span>Ionization cross sections of the Au L subshells by <span class="hlt">electron</span> impact from the L3 threshold to 100 <span class="hlt">keV</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barros, Suelen F.; Vanin, Vito R.; Maidana, Nora L.; Martins, Marcos N.; García-Alvarez, Juan A.; Santos, Osvaldo C. B.; Rodrigues, Cleber L.; Koskinas, Marina F.; Fernández-Varea, José M.</p> <p>2018-01-01</p> <p>We measured the cross sections for Au Lα, Lβ, Lγ, Lℓ and Lη x-ray production by the impact of <span class="hlt">electrons</span> with energies from the L3 threshold to 100 <span class="hlt">keV</span> using a thin Au film whose mass thickness was determined by Rutherford Backscattering Spectrometry. The x-ray spectra were acquired with a Si drift detector, which allowed to separate the components of the Lγ multiplet lines. The measured Lα, Lβ, {{L}}{γ }1, L{γ }{2,3,6}, {{L}}{γ }{4,4\\prime }, {{L}}{γ }5, {{L}}{\\ell } and Lη x-ray production cross sections were then employed to derive Au L1, L2 and L3 subshell ionization cross sections with relative uncertainties of 8%, 7% and 7%, respectively; these figures include the uncertainties in the atomic relaxation parameters. The correction for the increase in <span class="hlt">electron</span> path length inside the Au film was estimated by means of Monte Carlo simulations. The experimental ionization cross sections are about 10% above the state-of-the-art distorted-wave calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.1827C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.1827C"><span>The quiet evening <span class="hlt">auroral</span> arc and the structure of the growth phase near-Earth plasma sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coroniti, F. V.; Pritchett, P. L.</p> <p>2014-03-01</p> <p>The plasma pressure and current configuration of the near-Earth plasma sheet that creates and sustains the quiet evening <span class="hlt">auroral</span> arc during the growth phase of magnetospheric substorms is investigated. We propose that the quiet evening arc (QEA) connects to the thin near-Earth current sheet, which forms during the development of the growth phase enhancement of convection. The current sheet's large polarization electric fields are shielded from the ionosphere by an Inverted-V parallel potential drop, thereby producing the <span class="hlt">electron</span> precipitation responsible for the arc's luminosity. The QEA is located in the plasma sheet region of maximal radial pressure gradient and, in the east-west direction, follows the vanishing of the approximately dawn-dusk-directed gradient or fold in the plasma pressure. In the evening sector, the boundary between the Region1 and Region 2 current systems occurs where the pressure maximizes (approximately radial gradient of the pressure vanishes) and where the approximately radial gradient of the magnetic flux tube volume also vanishes in an inflection region. The proposed intricate balance of plasma sheet pressure and currents may well be very sensitive to disruption by the arrival of equatorward traveling <span class="hlt">auroral</span> streamers and their associated earthward traveling dipolarization fronts.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005SPIE.5650...64Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005SPIE.5650...64Y"><span>Optimization of single <span class="hlt">keV</span> ion implantation for the construction of single P-donor devices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Changyi; Jamieson, David N.; Hopf, Toby; Andresen, Soren E.; Hearne, Sean M.; Hudson, Fay E.; Pakes, Christopher I.; Mitic, Mladen; Gauja, Eric; Tamanyan, Grigori; Dzurak, Andrew S.; Prawer, Steven; Clark, Robert G.</p> <p>2005-02-01</p> <p>We report recent progress in single <span class="hlt">keV</span> ion implantation and online detection for the controlled implantation of single donors in silicon. When integrated with silicon nanofabrication technology this forms the "top down" strategy for the construction of prototype solid state quantum computer devices based on phosphorus donors in silicon. We have developed a method of single ion implantation and online registration that employs detector electrodes adjacent to the area into which the donors are to be implanted. The implantation sites are positioned with nanometer accuracy using an <span class="hlt">electron</span> beam lithography patterned PMMA mask. Control of the implantation depth of 20 nm is achieved by tuning the phosphorus ion energy to 14 <span class="hlt">keV</span>. The counting of single ion implantation in each site is achieved by the detection of e-/h+ pairs produced by the implanted phosphorus ion in the substrate. The system is calibrated by use of Mn K-line x-rays (5.9 and 6.4 <span class="hlt">keV</span>) and we find the ionization energy of the 14 <span class="hlt">keV</span> phosphorus ions in silicon to be about 3.5-4.0 <span class="hlt">keV</span> for implants through a 5 nm SiO2 surface layer. This paper describes the development of an improved PIN detector structure that provides more reliable performance of the earlier MOS structure. With the new structure, the energy noise threshold has been minimized to 1 <span class="hlt">keV</span> or less. Unambiguous detection/counting of single <span class="hlt">keV</span> ion implantation events were achieved with a confidence level greater than 98% with a reliable and reproducible fabrication process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ResPh...7..272A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ResPh...7..272A"><span>Gamma ray interaction studies of organic nonlinear optical materials in the energy range 122 <span class="hlt">keV</span>-1330 <span class="hlt">keV</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Awasarmol, V. V.; Gaikwad, D. K.; Raut, S. D.; Pawar, P. P.</p> <p></p> <p>The mass attenuation coefficients (μm) for organic nonlinear optical materials measured at 122-1330 <span class="hlt">keV</span> photon energies were investigated on the basis of mixture rule and compared with obtained values of WinXCOM program. It is observed that there is a good agreement between theoretical and experimental values of the samples. All samples were irradiated with six radioactive sources such as 57Co, 133Ba, 22Na, 137Cs, 54Mn and 60Co using transmission arrangement. Effective atomic and <span class="hlt">electron</span> numbers or <span class="hlt">electron</span> densities (Zeff and Neff), molar extinction coefficient (ε), mass energy absorption coefficient (μen/ρ) and effective atomic energy absorption cross section (σa,en) were determined experimentally and theoretically using the obtained μm values for investigated samples and graphs have been plotted. The graph shows that the variation of all samples decreases with increasing photon energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986PhDT........51M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986PhDT........51M"><span><span class="hlt">Electron</span> Echo 6 - a Study by Particle Detectors of <span class="hlt">Electrons</span> Artificially Injected Into the Magnetosphere.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malcolm, Perry Robert</p> <p></p> <p>The ECHO-6 sounding rocket was launched from the Poker Flat Research Range, Alaska on 30 March 1983. A Terrier-Black Brant launch vehicle carried the payload on a northward trajectory over an <span class="hlt">auroral</span> arc and to an apogee of 216 kilometers. The primary objective of the ECHO-6 experiment was to evaluate electric fields, magnetic fields, and plasma processes in the distant magnetosphere by injecting <span class="hlt">electron</span> beams in the ionosphere and observing conjugate echoes. The experiment succeeded in injecting 10-36 <span class="hlt">KeV</span> beams during the existence of a moderate growth phase aurora, an easterly electrojet system, and a pre -midnight inflation condition of the magnetosphere. The ECHO-6 payload system consisted of an accelerator MAIN payload, a free-flying Plasma Diagnostics Package (PDP), and four rocket propelled Throw Away Detectors (TADs). The PDP was ejected from the MAIN payload to analyze electric fields, plasma particles, energetic <span class="hlt">electrons</span>, and photometric effects produced by beam injections. The TADs were ejected from the MAIN payload in a pattern to detect echoes in the conjugate echo region south of the beam emitting MAIN payload. The TADs reached distances exceeding 3 kilometers from the MAIN payload and made measurements of the ambient <span class="hlt">electrons</span> by means of solid state detectors and electrostatic analyzers. In spite of the perfect operation of the TAD system and a rigorous analysis of the particle data, no conjugate echoes have been identified. Through the use of a new dynamic magnetic field model (Olson and Pfitzer, 1982) and satellite magnetometer measurements, it has been determined that the echoing <span class="hlt">electrons</span> returned out of range of the TADs as a result of their bounce times and curvature-gradient drifts being increased beyond the expected limits for an inflated magnetic field. This dynamic model was then applied to the study of echoes seen during the ECHO-4 flight resulting in a significant increase in the calculated energy of the echo <span class="hlt">electrons</span> and better</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007CosRe..45..248K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007CosRe..45..248K"><span>Observations of the <span class="hlt">auroral</span> hectometric radio emission onboard the INTERBALL-1 satellite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuril'Chik, V. N.</p> <p>2007-06-01</p> <p>The results of five-year (1995 2000) continuous observations of the <span class="hlt">auroral</span> radio emission (ARE) in the hectometric wavelength range on the high-apogee INTERBALL-1 satellite are presented. Short intense bursts of the <span class="hlt">auroral</span> hectometric radio emission (AHR) were observed at frequencies of 1463 and 1501 kHz. The bursts were observed predominantly at times when the terrestrial magnetosphere was undisturbed (in the quiet Sun period), and their number decreased rapidly with increasing solar activity. The bursts demonstrated seasonal dependence in the Northern and Southern hemispheres (dominating in the autumn-winter period). Their appearance probably depends on the observation time (UT). A qualitative explanation of the AHR peculiarities is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA43B2658S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA43B2658S"><span>Improved Background Removal in Sounding Rocket Neutral Atom Imaging Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, M. R.; Rowland, D. E.</p> <p>2017-12-01</p> <p>The VISIONS sounding rocket, launched into a substorm on Feb 7, 2013 from Poker Flat, Alaska had a novel miniaturized energetic neutral atom (ENA) imager onboard. We present further analysis of the ENA data from this rocket flight, including improved removal of ultraviolet and <span class="hlt">electron</span> contamination. In particular, the relative error source contributions due to geocoronal, <span class="hlt">auroral</span>, and airglow UV, as well as energetic <span class="hlt">electrons</span> from 10 eV to 3 <span class="hlt">keV</span> were assessed. The resulting data provide a more clear understanding of the spatial and temporal variations of the ion populations that are energized to tens or hundreds of eV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRA..11612232N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRA..11612232N"><span>Substorm and magnetosphere characteristic scales inferred from the SuperMAG <span class="hlt">auroral</span> electrojet indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newell, P. T.; Gjerloev, J. W.</p> <p>2011-12-01</p> <p>A generalization of the traditional 12-station <span class="hlt">auroral</span> electrojet (AE) index to include more than 100 magnetometer stations, SME, is an excellent predictor of global <span class="hlt">auroral</span> power (AP), even at high cadence (1 min). We use this index, and a database of more than 53,000 substorms derived from it, covering 1980-2009, to investigate time and energy scales in the magnetosphere, during substorms and otherwise. We find, contrary to common opinion, that substorms do not have a preferred recurrence rate but instead have two distinct dynamic regimes, each following a power law. The number of substorms recurring after a time Δt, N(Δt), varies as Δt-1.19 for short times (<80 min) and as Δt-1.76 for longer times (>3 hours). Other evidence also shows these distinct regimes for the magnetosphere, including a break in the power law spectra for SME at about 3 hours. The time between two consecutive substorms is only weakly correlated (r = 0.18 for isolated and r = 0.06 for recurrent) with the time until the next, suggesting quasiperiodicity is not common. However, substorms do have a preferred size, with the typical peak SME magnitude reaching 400-600 nT, but with a mean of 656 nT, corresponding to a bit less than 40 GW AP. More surprisingly, another characteristic scale exists in the magnetosphere, namely, a peak in the SME distribution around 61 nT, corresponding to about 5 GW precipitating AP. The dominant form of <span class="hlt">auroral</span> precipitation is diffuse aurora; thus, these values are properties of the magnetotail thermal <span class="hlt">electron</span> distribution. The characteristic 5 GW value specifically represents a preferred minimum below which the magnetotail rarely drops. The magnetotail experiences continuous loss by precipitation, so the existence of a preferred minimum implies driving that rarely disappears altogether. Finally, the distribution of SME values across all times, in accordance with earlier work on AE, is best fit by the sum of two distributions, each normal in log(SME). The lower</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM43B4286Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM43B4286Z"><span>Characteristics of Pitch Angle Distributions of 100s <span class="hlt">Kev</span> <span class="hlt">Electrons</span> in the Slot Region and Inner Radiation Belt­­­­­­­­</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, H.; Li, X.; Blake, J. B.; Fennell, J.; Claudepierre, S. G.; Baker, D. N.; Jaynes, A. N.; Malaspina, D.</p> <p>2014-12-01</p> <p>The pitch angle distribution (PAD) of energetic <span class="hlt">electrons</span> in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state-of-art pitch-angle-resolved data from the Magnetic <span class="hlt">Electron</span> Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes, a detailed analysis of 100s <span class="hlt">keV</span> <span class="hlt">electron</span> PADs below L =4 is performed, in which the PADs is categorized into three types: normal (flux peaking at 90°), cap (exceedingly peaking narrowly around 90°) and 90°-minimum (lower flux at 90°) PADs. By examining the characteristics of the PADs of 460 <span class="hlt">keV</span> <span class="hlt">electrons</span> for over a year, we find that the 90°-minimum PADs are generally present in the inner belt (L<2), while normal PADs dominate at L~3.5-4. In the region between, 90°-minimum PADs dominate during injection times and normal PADs dominate during quiet times. Cap PADs appear mostly at the decay phase of storms in the slot region and are likely caused by the pitch angle scattering of hiss waves. Fitting the normal PADs into sinnα form, the parameter n is much higher below L=3 than that in the outer belt and relatively constant in the inner belt but changes significantly in the slot region (2<L<3) during injection times. As for the 90°-minimum PADs, by performing a detailed case study, we find in the slot region this type of PAD is likely caused by chorus wave heating, but this mechanism can hardly explain the formation of 90°-minimum PADs at the center of inner belt. These new and compelling observations, made possible by the high-quality measurements of MagEIS, present a challenge for the wave modelers, and future work is still needed to fully understand them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhyB..326...51P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhyB..326...51P"><span>Muonium formation at <span class="hlt">keV</span> energies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prokscha, T.; Morenzoni, E.; Garifianov, N.; Glückler, H.; Khasanov, R.; Luetkens, H.; Suter, A.</p> <p>2003-02-01</p> <p>Charge differentiation in μ + or muonium (Mu) as a consequence of the slowing down of μ + in matter is of fundamental interest in the μSR method. It is also of relevance for understanding the moderation process of μ + in van der Waals solids like s-Ne, s-Ar or s-N 2, which are the most suitable materials to generate epithermal μ + serving as a source for low-energy μ + (LE-μ +) beams. The LE-μ + beam at the Paul Scherrer Institut (PSI) allows us to study the formation of Mu at low implantation energies (0.5- 30 <span class="hlt">keV</span>) in insulators and semiconductors. These investigations may help to clarify the interaction between the μ + and the <span class="hlt">electrons</span> of its ionisation track since the number of track <span class="hlt">electrons</span> can be tuned by varying the implantation energy. We present the first results of LE-μSR investigations on thin van der Waals solids (s-Ar, s-Xe), fused quartz ( SUPRASIL) and a quartz crystal, where the μ + and Mu fractions were measured as a function of the implantation energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980ESASP.152.....H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980ESASP.152.....H"><span><span class="hlt">Auroral</span> particle acceleration: An example of a universal plasma process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haerendel, G.</p> <p>1980-06-01</p> <p>The occurrence of discrete and narrow <span class="hlt">auroral</span> arcs is attributed to a sudden release of magnetic tensions set up in a magnetospheric-ionospheric current circuit of high strength. At altitudes of several 1000 km the condition of frozen in magnetic fields can be broken temporarily in thin regions corresponding to the observed width of <span class="hlt">auroral</span> arcs. This implies magnetic field-aligned potential drops of several kilovolts supported by certain anomalous transport processes which can only be maintained in a quasi-stationary fashion if the current density exceeds a critical limit. The region of field aligned potential drops is structured by two pairs of standing waves which are generalized Alfven waves of large amplitude across which the parallel electric field has a finite jump. The waves are emitted from the leading edge of the acceleration region which propagates slowly into the stressed magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA111640','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA111640"><span>Atmospheric Pressure and Velocity Fluctuations Near the <span class="hlt">Auroral</span> Electrojet.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1982-01-15</p> <p>various aspects of the atmosphere’s dynamical response to <span class="hlt">auroral</span> activity have been carried out by Blumen and Hendl (1969), Testud (1970), Francis...Geophys. Res. 80, 2839, 1975. Testud , 3., Gravity waves generated during magnetic substorms, 3. Atmos. Terr. Phys. 32, 1793, 1970. Waco, D. E., A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFMSA21A..09P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFMSA21A..09P"><span>A Multi-spacecraft Study of the Magnetospheric Influence on Ionospheric Chemistry - a Detailed Examination of Recent Geomagnetically Active Periods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrinec, S. M.; Chenette, D. L.; Imhof, W. L.; Baker, D. N.; Barth, C. A.; Mankoff, K. D.; Luhmann, J. G.; Mason, G. M.; Mazur, J. E.; Evans, D. S.</p> <p>2001-12-01</p> <p>A detailed analysis of the particle precipitation into the <span class="hlt">auroral</span> regions during specific storm intervals is performed. The global energetic particle input to the ionosphere and lower thermosphere is provided by several monitors; namely the Polar Ionospheric X-ray Experiment (PIXIE) on board the NASA/GGS Polar satellite (for inferred <span class="hlt">electron</span> energies greater than about 3 <span class="hlt">keV</span>); the TED sensor system on board the NOAA/Polar Orbiting Environmental Satellite (POES) (particle energies between about 50 eV and 20 <span class="hlt">keV</span>), and the sensor system (LICA) on board the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) spacecraft (for <span class="hlt">electron</span> energies greater then 25 <span class="hlt">keV</span>). Changes in nitric oxide (NO) densities at altitudes between 97 and 150 km during these storm intervals are studied using observations from the Student Nitric Oxide Explorer (SNOE). Solar wind observations are also used to provide important information regarding the external drivers for the magnetospheric input to the upper atmosphere. Specific intervals of examination include the recent large geomagnetic event of March 31-April 1, 2001, and other events from the most recent solar maximum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA012476','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA012476"><span><span class="hlt">Auroral</span> Simulation Studies. HAES Report No. 6</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1975-04-22</p> <p>Kofsky and John Schroeder (Photomctrics). Benefit was also derived from conversations with Drs; A. T. Stair (AFCRL), Richard Hegblom (Boston College...rate at 1.27 pm) about 35 minutes following <span class="hlt">auroral</span> onset. This is consistent -with the observations of Gattinger and Vallance Jones (Reference 26). The...above lead to the results shown in Fi&.ee 2-42. Shown for comparison are the observations of Gattinger and Vallance Jones. The measured maximum ground</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100033332','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100033332"><span>Cluster in the <span class="hlt">Auroral</span> Acceleration Region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickett, Jolene S.; Fazakerley, Andrew N.; Marklund, Gorun; Dandouras, Iannis; Christopher, Ivar W.; Kistler, Lynn; Lucek, Elizabeth; Masson, Arnaud; Taylor, Matthew G.; Mutel, Robert L.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20100033332'); toggleEditAbsImage('author_20100033332_show'); toggleEditAbsImage('author_20100033332_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20100033332_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20100033332_hide"></p> <p>2010-01-01</p> <p>Due to a fortuitous evolution of the Cluster orbit, the Cluster spacecraft penetrated for the first time in its mission the heart of Earth's <span class="hlt">auroral</span> acceleration region (AAR) in December 2009 and January 2010. During this time a special AAR campaign was carried out by the various Cluster instrument teams with special support from ESA and NASA facilities. We present some of the first multi-spacecraft observations of the waves, particles and fields made during that campaign. The Cluster spacecraft configuration during these AAR passages was such that it allowed us to explore the differences in the signatures of waves, particles, and fields on the various spacecraft in ways not possible with single spacecraft. For example, one spacecraft was more poleward than the other three (C2), one was at higher altitude (C1), and one of them (0) followed another (C4) through the AAR on approximately the same track but delayed by three minutes. Their separations were generally on the order of a few thousand km or less and occasionally two of them were lying along the same magnetic field line. We will show some of the first analyses of the data obtained during the AAR campaign, where upward and downward current regions, and the waves specifically associated with those regions, as well as the <span class="hlt">auroral</span> cavities, were observed similarly and differently on the various spacecraft, helping us to explore the spatial, as well as the temporal, aspects of processes occurring in the AAR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM53A..09G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM53A..09G"><span>Data-driven local-scale modeling of ionospheric responses to <span class="hlt">auroral</span> forcing using incoherent scatter radar and ground-based imaging measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grubbs, G. A., II; Zettergren, M. D.; Samara, M.; Michell, R.; Hampton, D. L.; Lynch, K. A.; Varney, R. H.; Reimer, A.; Burleigh, M.</p> <p>2017-12-01</p> <p>The aurora encapsulates a wide range of spatial and temporal scale sizes, particularly during active events such as those that exist during substorm expansion. Of interest to the present work are ionospheric responses to magnetospheric forcing at relatively small scales (0.5-20 km), including formation of structured <span class="hlt">auroral</span> arc current systems, ion frictional heating, upflow, and density cavity formation among other processes. Even for carefully arranged experiments, it is often difficult to fully assess physical details (time evolution, causality, unobservable parameters) associated with these types of responses, thus highlighting the general need for high-resolution modeling efforts to support the observations. In this work, we develop and test a local-scale model to describe effects of precipitating <span class="hlt">electrons</span> and electric fields on the ionospheric plasma responses using available remote sensing data (e.g. from ISRs and filtered cameras). Our model is based on a 3D multi-fluid/electrostatic ionospheric model, GEMINI (Zettergren et al., 2015), coupled a two-stream <span class="hlt">electron</span> transport code which produces <span class="hlt">auroral</span> intensities, impact ionization, and thermal <span class="hlt">electron</span> heating GLobal airglOW (GLOW; Solomon, 2017). GEMINI-GLOW thus describes both thermal and suprathermal effects on the ionosphere and is driven by boundary conditions consisting of topside ionospheric field-aligned currents and suprathermal <span class="hlt">electrons</span>. These boundary conditions are constrained using time and space-dependent electric field and precipitation estimates from recent sounding rocket campaigns, ISINGLASS (02 March 2017) and GREECE (03 March 2014), derived from the Poker Flat incoherent scatter radar (PFISR) drifts and filtered EMCCD cameras respectively. Results from these data-driven case studies are compared to plasma parameter responses (i.e. density and temperature) independently estimated by PFISR and from the sounding rockets. These studies are intended as a first step towards a local</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.8108A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.8108A"><span>The magnetic local time distribution of energetic <span class="hlt">electrons</span> in the radiation belt region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allison, Hayley J.; Horne, Richard B.; Glauert, Sarah A.; Zanna, Giulio Del</p> <p>2017-08-01</p> <p>Using 14 years of <span class="hlt">electron</span> flux data from the National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites, a statistical study of the magnetic local time (MLT) distribution of the <span class="hlt">electron</span> population is performed across a range of activity levels, defined by AE, AE*, Kp, solar wind velocity (Vsw), and VswBz. Three <span class="hlt">electron</span> energies (>30, >100, and >300 <span class="hlt">keV</span>) are considered. Dawn-dusk flux asymmetries larger than order of magnitude were observed for >30 and >100 <span class="hlt">keV</span> <span class="hlt">electrons</span>. For >300 <span class="hlt">keV</span> <span class="hlt">electrons</span>, dawn-dusk asymmetries were primarily due to a decrease in the average duskside flux beyond L* ˜ 4.5 that arose with increasing activity. For the >30 <span class="hlt">keV</span> population, substorm injections enhance the dawnside flux, which may not reach the duskside as the <span class="hlt">electrons</span> can be on open drift paths and lost to the magnetopause. The asymmetries in the >300 <span class="hlt">keV</span> population are attributed to the combination of magnetopause shadowing and >300 <span class="hlt">keV</span> <span class="hlt">electron</span> injections by large electric fields. We suggest that 3-D radiation belt models could set the minimum energy boundary (Emin) to 30 <span class="hlt">keV</span> or above at L* ˜ 6 during periods of low activity. However, for more moderate conditions, Emin should be larger than 100 <span class="hlt">keV</span> and, for very extreme activities, ˜300 <span class="hlt">keV</span>. Our observations show the extent that in situ <span class="hlt">electron</span> flux readings may vary during active periods due to the MLT of the satellite and highlight the importance of 4-D radiation belt models to fully understand radiation belt processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM43B2711A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM43B2711A"><span>The Magnetic Local Time Distribution of Energetic <span class="hlt">Electrons</span> in the Radiation Belt Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allison, H. J.</p> <p>2017-12-01</p> <p>Using fourteen years of <span class="hlt">electron</span> flux data from the National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites (POES), a statistical study of the magnetic local time (MLT) distribution of the <span class="hlt">electron</span> population is performed across a range of activity levels, defined by AE, AE*, Kp, solar wind velocity (Vsw), and VswBz. Three <span class="hlt">electron</span> energies (>30, >100, and >300 <span class="hlt">keV</span>) are considered. Dawn-dusk flux asymmetries larger than order of magnitude were observed for >30 and >100 <span class="hlt">keV</span> <span class="hlt">electrons</span>. For >300 <span class="hlt">keV</span> <span class="hlt">electrons</span>, dawn-dusk asymmetries were primarily due to a decrease in the average dusk-side flux beyond L* ˜ 4.5 that arose with increasing activity. For the >30 <span class="hlt">keV</span> population, substorm injections enhance the dawn-side flux, which may not reach the dusk-side as the <span class="hlt">electrons</span> can be on open drift paths and lost to the magnetopause. The asymmetries in the >300 <span class="hlt">keV</span> population are attributed to the combination of magnetopause shadowing and >300 <span class="hlt">keV</span> <span class="hlt">electron</span> injections by large electric fields. We suggest that 3D radiation belt models could set the minimum energy boundary (Emin) to 30 <span class="hlt">keV</span> or above at L* ˜6 during periods of low activity. However, for more moderate conditions, Emin should be larger than 100 <span class="hlt">keV</span> and, for very extreme activities, ˜300 <span class="hlt">keV</span>. Our observations show the extent that in-situ <span class="hlt">electron</span> flux readings may vary during active periods due to the MLT of the satellite and highlight the importance of 4D radiation belt models to fully understand radiation belt processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P31C2839D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P31C2839D"><span>Jupiter's X-ray <span class="hlt">Auroral</span> Pulsations and Spectra During Juno Perijove 7</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dunn, W.; Branduardi-Raymont, G.; Ray, L. C.; Jackman, C. M.; Kraft, R.; Gladstone, R.; Yao, Z.; Rae, J.; Gray, R.; Elsner, R.; Grodent, D. C.; Nichols, J. D.; Ford, P. G.; Ness, J. U.; Kammer, J.; Rodriguez, P.</p> <p>2017-12-01</p> <p>Jupiter's X-ray aurora is concentrated into a bright and dynamic hot spot that is produced by precipitating 10 MeV ions [Gladstone et al. 2002; Elsner et al. 2005; Branduardi-Raymont et al. 2007]. These highly energetic emissions exhibit pulsations over timescales of 10s of minutes and change morphology, intensity and precipitating particle populations from observation to observation and pole to pole [e.g. Dunn et al. 2016; in-press]. The acceleration process/es that allow Jupiter to produce these high-energy ion charge exchange emissions are not well understood, but are concentrated in the most poleward regions of the aurora, where field lines map to the outer magnetosphere and possibly beyond [Vogt et al. 2015; Kimura et al. 2016]. On July 11th 2017, NASA's Juno spacecraft conducted its 7th perijove flyby of Jupiter and is predicted to have flown directly through field lines that map to the Northern and Southern X-ray hot spots. During this unique flight, the XMM-Newton observatory conducted 40 hours of continuous time-tagged X-ray observations. We present the results from these X-ray observations, showing that Jupiter's X-ray aurora varies significantly from one planetary rotation to the next and that the spectral signatures, indicative of the precipitating ion and <span class="hlt">electron</span> populations producing the emission, also vary. We measure the Doppler broadening of the spectral lines to calculate the ion energies at the point when they impact the ionosphere, in order that these might be compared with in-situ data to constrain Jovian <span class="hlt">auroral</span> acceleration processes. Finally, we compare X-ray signatures from the last decade of observations with UV polar emissions at similar times to further enrich multi-wavelength connections and deepen our understanding of how Jupiter is able to generate its highly energetic polar <span class="hlt">auroral</span> precipitations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRA..123..385L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRA..123..385L"><span>The Effects of Solar Wind Dynamic Pressure Changes on the Substorm Auroras and Energetic <span class="hlt">Electron</span> Injections on 24 August 2005</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, L. Y.; Wang, Z. Q.</p> <p>2018-01-01</p> <p>After the passage of an interplanetary (IP) shock at 06:13 UT on 24 August 2005, the enhancement (>6 nPa) of solar wind dynamic pressure and the southward turning of interplanetary magnetic field (IMF) cause the earthward movement of dayside magnetopause and the drift loss of energetic particles near geosynchronous orbit. The persistent <span class="hlt">electron</span> drift loss makes the geosynchronous satellites cannot observe the substorm <span class="hlt">electron</span> injection phenomenon during the two substorm expansion phases (06:57-07:39 UT) on that day. Behind the IP shock, the fluctuations ( 0.5-3 nPa) of solar wind dynamic pressure not only alter the dayside <span class="hlt">auroral</span> brightness but also cause the entire <span class="hlt">auroral</span> oval to swing in the day-night direction. However, there is no Pi2 pulsation in the nightside <span class="hlt">auroral</span> oval during the substorm growth phase from 06:13 to 06:57 UT. During the subsequent two substorm expansion phases, the substorm expansion activities cause the nightside aurora oval brightening from substorm onset site to higher latitudes, and meanwhile, the enhancement (decline) of solar wind dynamic pressure makes the nightside <span class="hlt">auroral</span> oval move toward the magnetic equator (the magnetic pole). These observations demonstrate that solar wind dynamic pressure changes and substorm expansion activities can jointly control the luminosity and location of the nightside <span class="hlt">auroral</span> oval when the internal and external disturbances occur simultaneously. During the impact of a strong IP shock, the earthward movement of dayside magnetopause probably causes the disappearance of the substorm <span class="hlt">electron</span> injections near geosynchronous orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AnGeo..28.1167G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AnGeo..28.1167G"><span>Response of the <span class="hlt">auroral</span> electrojet indices to abrupt southward IMF turnings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gjerloev, J. W.; Hoffman, R. A.; Ohtani, S.; Weygand, J.; Barnes, R.</p> <p>2010-05-01</p> <p>We present results from a study of the behavior of the <span class="hlt">auroral</span> electrojet indices following abrupt southward turnings of the IMF Bz. The <span class="hlt">auroral</span> electrojet indices are calculated from observations made by more than 100 ground based stations provided by the SuperMAG collaborators. Based on three simple criteria we selected 73 events. In each event the interval of analysis started at the time of the IMF Bz southward turning and ended 45 minutes later or at the onset of any abrupt energy unloading event in the magnetosphere, regardless of size. We refer to this period as the "pre-unloading phase". To isolate the dependence of the <span class="hlt">auroral</span> electrojets on the solar induced ionospheric conductivity during this phase we separated the standard AU/AL indices into two new sets of indices defined by the upper and lower envelope of the north-south component for all sunlit stations (AUs/ALs) and for all stations in darkness (AUd/ALd). Based on events and statistical analyses we can conclude that following a southward turning of the IMF Bz the AUd/ALd indices show no measurable response while the AUs/ALs indices clearly intensify. The intensifications of AUs/ALs are dependent on the intensity of the solar wind driver (as measured by IMF Bz or the Akasofu ɛ parameter). The lack of AUd/ALd response does not depend on the intensity of any subsequent substorm. We find that during these isolated events the ionospheric current system is primarily confined to the sunlit ionosphere. This truncated version of the classical global DP-2 current system suggests that <span class="hlt">auroral</span> electrojet continuity is not maintained across the terminator. Because of its conductivity dependence on the solar zenith angle, this truncated global current pattern is expected to be highly dependent on UT and season and thus can be asymmetric between hemispheres. Thus we argue that the global two-cell DP-2 current system is not a consequence only of a southward turning of the IMF but requires also the reduction of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002877','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002877"><span>HST/STIS Observations of Ganymede's <span class="hlt">Auroral</span> Ovals at Eastern Elongation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Saur, J.; Duling, S.; Roth, L.; Feldman, P. D.; Strobel, D. F.; Retherford, K. D.; McGrath, M. A.; Wennmacher, A.</p> <p>2011-01-01</p> <p>We report on new Space Telescope Imaging Spectrograph (STIS) observations of Ganymede s <span class="hlt">auroral</span> emissions obtained (to be obtained) during two visits with the Hubble Space Telescope (HST). The observations of the first visit, a five orbits, were obtained on November 19, 2010 and the second visit, also a five orbits, is scheduled for opposition in October/November 2011. We will present results of the full campaign, in case of a successful execution of the second visit. Our observations cover more than half a cycle of system III longitudes of Ganymede s positions within Jupiter s magnetosphere for each visit. We analyze the observations with respect to brightness and locations of Ganymede <span class="hlt">auroral</span> ovals. Our goal is to set constrains on the interaction of Ganymede s mini-magnetosphere with Jupiter s magnetosphere, Ganymede s magnetic field and plasma environment, and if possible on Ganymede s neutral atmosphere.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720005092','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720005092"><span>Local-time survey of plasma at low altitudes over the <span class="hlt">auroral</span> zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frank, L. A.; Ackerson, K. L.</p> <p>1971-01-01</p> <p>A local-time survey of the low energy proton and <span class="hlt">electron</span> intensities precipitated into the earth's atmosphere during periods of magnetic quiescence was constructed. A typical, individual satellite crossing of this region in each of eight local-time sectors was selected from a library of similar observations with the polar-orbiting satellite Injun 5. The trapping boundary for more energetic <span class="hlt">electron</span> intensities, E 45 <span class="hlt">keV</span>, is a natural coordinate for delineating the boundary between the two major types of lower energy, 50 or = E or = 15,000 eV. The main contributors to <span class="hlt">electron</span> energy influx are inverted V precipitation poleward of the trapping boundary and the plasma sheet intensities equatorward. These are interpreted in terms of a magnetospheric model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170003140&hterms=energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Denergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170003140&hterms=energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Denergy"><span><span class="hlt">Electron</span> Flux Models for Different Energies at Geostationary Orbit</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boynton, R. J.; Balikhin, M. A.; Sibeck, D. G.; Walker, S. N.; Billings, S. A.; Ganushkina, N.</p> <p>2016-01-01</p> <p>Forecast models were derived for energetic <span class="hlt">electrons</span> at all energy ranges sampled by the third-generation Geostationary Operational Environmental Satellites (GOES). These models were based on Multi-Input Single-Output Nonlinear Autoregressive Moving Average with Exogenous inputs methodologies. The model inputs include the solar wind velocity, density and pressure, the fraction of time that the interplanetary magnetic field (IMF) was southward, the IMF contribution of a solar wind-magnetosphere coupling function proposed by Boynton et al. (2011b), and the Dst index. As such, this study has deduced five new 1 h resolution models for the low-energy <span class="hlt">electrons</span> measured by GOES (30-50 <span class="hlt">keV</span>, 50-100 <span class="hlt">keV</span>, 100-200 <span class="hlt">keV</span>, 200-350 <span class="hlt">keV</span>, and 350-600 <span class="hlt">keV</span>) and extended the existing >800 <span class="hlt">keV</span> and >2 MeV Geostationary Earth Orbit <span class="hlt">electron</span> fluxes models to forecast at a 1 h resolution. All of these models were shown to provide accurate forecasts, with prediction efficiencies ranging between 66.9% and 82.3%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850062284&hterms=conjunctions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dconjunctions','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850062284&hterms=conjunctions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dconjunctions"><span><span class="hlt">Auroral</span> zone electric fields from DE 1 and 2 at magnetic conjunctions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weimer, D. R.; Goertz, C. K.; Gurnett, D. A.; Maynard, N. C.; Burch, J. L.</p> <p>1985-01-01</p> <p>Nearly simultaneous measurements of <span class="hlt">auroral</span> zone electric fields are obtained by the Dynamics Explorer spacecraft at altitudes below 900 km and above 4,500 km during magnetic conjunctions. The measured electric fields are usually perpendicular to the magnetic field lines. The north-south meridional electric fields are projected to a common altitude by a mapping function which accounts for the convergence of the magnetic field lines. When plotted as a function of invariant latitude, graphs of the projected electric fields measured by both DE-1 and DE-2 show that the large-scale electric field is the same at both altitudes, as expected. Superimposed on the large-scale fields, however, are small-scale features with wavelengths less than 100 km which are larger in magnitude at the higher altitude. Fourier transforms of the electric fields show that the magnitudes depend on wavelength. Outside of the <span class="hlt">auroral</span> zone the electric field spectrums are nearly identical. But within the <span class="hlt">auroral</span> zone the high and low altitude electric fields have a ratio which increases with the reciprocal of the wavelength. The small-scale electric field variations are associated with field-aligned currents. These currents are measured with both a plasma instrument and magnetometer on DE-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH21A2385W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH21A2385W"><span>The Energy Spectrum of Solar Energetic <span class="hlt">Electrons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, L.; Yang, L.; Krucker, S.; Wimmer-Schweingruber, R. F.; Bale, S. D.</p> <p>2015-12-01</p> <p>Here we present a statistical survey of the energy spectrum of solar energetic <span class="hlt">electron</span> events (SEEs) observed by the WIND 3DP instrument from 1995 though 2014. For SEEs with the minimum energy below 10 <span class="hlt">keV</span> and the maximum energy above 100 <span class="hlt">keV</span>, ~85% (~2%) have a double-power-law energy spectrum with a steepening (hardening) above the break energy, while ~13% have a single-power-law energy spectrum at all energies. The average spectral index is ~2.4 below the energy break and is ~4.0 above the energy break. For SEEs detected only at energies <10 <span class="hlt">keV</span> (>20 <span class="hlt">keV</span>), they generally show a single-power-law spectrum with the average index of ~3.0 (~3.3). The spectrum of SEEs detected only below 10 <span class="hlt">keV</span> appears to get harder with increasing solar activity, but the spectrum of SEEs with higher-energy <span class="hlt">electrons</span> shows no clear correlation with solar activity. We will also investigate whether the observed energy spectrum of SEEs at 1 AU mainly reflects the <span class="hlt">electron</span> acceleration at the Sun or the <span class="hlt">electron</span> transport in the interplanetary medium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19392121','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19392121"><span>Observation of large-scale density cavities and parametric-decay instabilities in the high-altitude discrete <span class="hlt">auroral</span> ionosphere under pulsed electromagnetic radiation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wong, A Y; Chen, J; Lee, L C; Liu, L Y</p> <p>2009-03-13</p> <p>A large density cavity that measured 2000 km across and 500 km in height was observed by DEMETER and Formosat/COSMIC satellites in temporal and spatial relation to a new mode of propagation of electromagnetic (em) pulses between discrete magnetic field-aligned <span class="hlt">auroral</span> plasmas to high altitudes. Recorded positive plasma potential from satellite probes is consistent with the expulsion of <span class="hlt">electrons</span> in the creation of density cavities. High-frequency decay spectra support the concept of parametric instabilities fed by free energy sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090020484','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090020484"><span>Disabling CNT <span class="hlt">Electronic</span> Devices by Use of <span class="hlt">Electron</span> Beams</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Petkov, Mihail</p> <p>2008-01-01</p> <p>Bombardment with tightly focused <span class="hlt">electron</span> beams has been suggested as a means of electrically disabling selected individual carbon-nanotubes (CNTs) in <span class="hlt">electronic</span> devices. Evidence in support of the suggestion was obtained in an experiment in which a CNT field-effect transistor was disabled (see figure) by focusing a 1-<span class="hlt">keV</span> <span class="hlt">electron</span> beam on a CNT that served as the active channel of a field-effect transistor (FET). Such bombardment could be useful in the manufacture of nonvolatile-memory circuits containing CNT FETs. Ultimately, in order to obtain the best <span class="hlt">electronic</span> performances in CNT FETs and other <span class="hlt">electronic</span> devices, it will be necessary to fabricate the devices such that each one contains only a single CNT as an active element. At present, this is difficult because there is no way to grow a single CNT at a specific location and with a specific orientation. Instead, the common practice is to build CNTs into <span class="hlt">electronic</span> devices by relying on spatial distribution to bridge contacts. This practice results in some devices containing no CNTs and some devices containing more than one CNT. Thus, CNT FETs have statistically distributed <span class="hlt">electronic</span> characteristics (including switching voltages, gains, and mixtures of metallic and semiconducting CNTs). According to the suggestion, by using a 1-<span class="hlt">keV</span> <span class="hlt">electron</span> beam (e.g., a beam from a scanning <span class="hlt">electron</span> microscope), a particular nanotube could be rendered electrically dysfunctional. This procedure could be repeated as many times as necessary on different CNTs in a device until all of the excess CNTs in the device had been disabled, leaving only one CNT as an active element (e.g., as FET channel). The physical mechanism through which a CNT becomes electrically disabled is not yet understood. On one hand, data in the literature show that <span class="hlt">electron</span> kinetic energy >86 <span class="hlt">keV</span> is needed to cause displacement damage in a CNT. On the other hand, inasmuch as a 1-<span class="hlt">keV</span> beam focused on a small spot (typically a few tens of nanometers wide</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990039172&hterms=hydra&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhydra','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990039172&hterms=hydra&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhydra"><span>Relationship of Topside Ionospheric Ion Outflows to <span class="hlt">Auroral</span> Forms and Precipitation, Plasma Waves, and Convection Observed by Polar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_19990039172'); toggleEditAbsImage('author_19990039172_show'); toggleEditAbsImage('author_19990039172_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_19990039172_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_19990039172_hide"></p> <p>1998-01-01</p> <p>The POLAR satellite often observes upflowing ionospheric ions (UFIs) in and near the aurora] oval on southern perigee (approx. 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with <span class="hlt">auroral</span> forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the duskside after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawnside during the recovery phase. The UFIs showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below approx. 10 kHz, while no significant <span class="hlt">auroral</span> activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped <span class="hlt">auroral</span> kilometric radiation (AKR) signatures observed above -200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating <span class="hlt">electrons</span> and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs, the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P33C2164B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P33C2164B"><span>Modelling the <span class="hlt">Auroral</span> Magnetosphere-Ionosphere Coupling System at Jupiter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bunce, E. J.; Cowley, S.; Provan, G.</p> <p>2016-12-01</p> <p>The magnetosphere-ionosphere coupling system at Jupiter is a topic of central significance in understanding the fundamental properties of its large-scale plasma environment. Theoretical discussion of this topic typically considers the properties of the field-aligned current systems that form part of a large-scale magnetosphere-ionosphere coupling current system associated with momentum exchange between the ionosphere and the magnetosphere, communicated via the magnetic field. The current system associated with the main oval is believed to be related to centrifugally-driven outward radial transport of iogenic plasma that leads to sub-corotation in the middle magnetosphere. In addition to the magnetosphere-ionosphere coupling current system, upward-directed field-aligned currents may flow at the open-closed field line boundary due to the shear between outer closed field lines and open field lines, which may relate to emission poleward of the main oval. An axi-symmetric model of the plasma flow in the jovian system, the related coupling currents, and the consequent <span class="hlt">auroral</span> precipitation based on these combined ideas was initially devised to represent typical steady-state conditions for the system and later extended to consider <span class="hlt">auroral</span> effects resulting from sudden compressions of the magnetosphere. More recently, the model has been extended along model magnetic field lines into the magnetosphere in order to relate them to in situ observations from the NASA Juno spacecraft at Jupiter. The field-aligned coupling currents associated with the modelled current systems produce a readily-observable azimuthal field signature that bends the field lines out of magnetic meridians. Here we show the computed azimuthal fields produced by our model <span class="hlt">auroral</span> current system throughout the region between the ionosphere and the magnetic equator, and illustrate the results by evaluation of various model parameters (e.g. field-aligned current density, accelerating voltages, accelerated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950053472&hterms=exponential+current&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dexponential%2Bcurrent','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950053472&hterms=exponential+current&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dexponential%2Bcurrent"><span>A correlative comparison of the ring current and <span class="hlt">auroral</span> electrojects usig geomagnetic indices</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cade, W. B., III; Sojka, J. J.; Zhu, L.</p> <p>1995-01-01</p> <p>From a study of the 21 largest geomagnetic storms during solar cycle 21, a strong correlation is established between the ring current index Dst and the time-weighted accumulation of the 1-hour <span class="hlt">auroral</span> electrojets indices, AE and AL. The time-weighted accumulation corresponds to convolution of the <span class="hlt">auroral</span> electrojet indices with an exponential weighting function with an e-folding time of 9.4 hours. The weighted indices AE(sub w) and AL(sub w) have correltation coefficients against Dst ranging between 0.8 and 0.95 for 20 of the 21 storms. Correlation over the entire solar cycle 21 database is also strong but not as strong as for an individual storm. A set of simple Dst prediction functions provide a first approximation of the inferred dependence, but the specific functional relationship of Dst (AL(sub w)) or Dst (AL(sub w)) varies from one storm to the next in a systematic way. This variation reveals a missing parametric dependence in the transfer function. However, our results indicate that <span class="hlt">auroral</span> electroject indices are potentially useful for predicting storm time enhancements of ring current intensity with a few hours lead time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...10428101L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...10428101L"><span>High-frequency and time resolution rocket observations of structured low- and medium-frequency whistler mode emissions in the <span class="hlt">auroral</span> ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>LaBelle, J.; McAdams, K. L.; Trimpi, M. L.</p> <p></p> <p>High bandwidth electric field waveform measurements on a recent <span class="hlt">auroral</span> sounding rocket reveal structured whistler mode signals at 400-800 kHz. These are observed intermittently between 300 and 500 km with spectral densities 0-10 dB above the detection threshold of 1.5×10-11V2/m2Hz. The lack of correlation with local particle measurements suggests a remote source. The signals are composed of discrete structures, in one case having bandwidths of about 10 kHz and exhibiting rapid frequency variations of the order of 200 kHz per 100 ms. In one case, emissions near the harmonic of the whistler mode signals are detected simultaneously. Current theories of <span class="hlt">auroral</span> zone whistler mode emissions have not been applied to explain quantitatively the fine structure of these signals, which resemble <span class="hlt">auroral</span> kilometric radiation (AKR) rather than <span class="hlt">auroral</span> hiss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110011013&hterms=statistics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dstatistics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110011013&hterms=statistics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dstatistics"><span>Multiscale <span class="hlt">Auroral</span> Emission Statistics as Evidence of Turbulent Reconnection in Earth's Midtail Plasma Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Klimas, Alex; Uritsky, Vadim; Donovan, Eric</p> <p>2010-01-01</p> <p>We provide indirect evidence for turbulent reconnection in Earth's midtail plasma sheet by reexamining the statistical properties of bright, nightside <span class="hlt">auroral</span> emission events as observed by the UVI experiment on the Polar spacecraft and discussed previously by Uritsky et al. The events are divided into two groups: (1) those that map to absolute value of (X(sub GSM)) < 12 R(sub E) in the magnetotail and do not show scale-free statistics and (2) those that map to absolute value of (X(sub GSM)) > 12 R(sub E) and do show scale-free statistics. The absolute value of (X(sub GSM)) dependence is shown to most effectively organize the events into these two groups. Power law exponents obtained for group 2 are shown to validate the conclusions of Uritsky et al. concerning the existence of critical dynamics in the <span class="hlt">auroral</span> emissions. It is suggested that the <span class="hlt">auroral</span> dynamics is a reflection of a critical state in the magnetotail that is based on the dynamics of turbulent reconnection in the midtail plasma sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996AnGeo..14.1124N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996AnGeo..14.1124N"><span>Application of stochastic inversion in <span class="hlt">auroral</span> tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nygrén, T.; Markkanen, M.; Lehtinen, M.; Kaila, K.</p> <p>1996-11-01</p> <p>A software package originally developed for satellite radio tomography is briefly introduced and its use in two-dimensional <span class="hlt">auroral</span> tomography is described. The method is based on stochastic inversion, i.e. finding the most probable values of the unknown volume emission rates once the optical measurements are made using either a scanning photometer or an <span class="hlt">auroral</span> camera. A set of simulation results is shown for a different number and separations of optical instruments at ground level. It is observed that arcs with a thickness of a few kilometers and separated by a few tens of kilometers are easily reconstructed. The maximum values of the inversion results, however, are often weaker than in the model. The most obvious reason for this is the grid size, which cannot be much smaller than the arc thickness. The grid necessarily generates a spatial averaging effect broadening the arc cross-sections and reducing the peak values. Finally, results from TV-camera observations at Tromsø and Esrange are shown. Although these sites are separated by more than 200 km, arcs close to Tromsø have been successfully reconstructed. Acknowledgements. The work done by P. Henelius and E. Vilenius in programme development is gratefully acknowledged. Topical Editor D. Alcayde thanks I. Pryse and A. Vallance-Jones for their help in evaluating this paper.--> Correspondence to: T. Nygrén--></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EPSC...11..388G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EPSC...11..388G"><span>Juno-UVS and Chandra Observations of Jupiter's Polar <span class="hlt">Auroral</span> Emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gladstone, G. R.; Kammer, J. A.; Versteeg, M. H.; Greathouse, T. K.; Hue, V.; Gérard, J.-C.; Grodent, D.; Bonfond, B.; Jackman, C.; Branduardi-Raymont, G.; Kraft, R. P.; Dunn, W. R.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.; Mauk, B. H.; Valek, P.; Adriani, A.; Kurth, W. S.; Orton, G. S.</p> <p>2017-09-01</p> <p>New results are presented comparing Jupiter's auroras at far-ultraviolet and x-ray wavelengths, using data acquired by Juno-UVS and Chandra. The highly variable polar auroras (which are located within the main <span class="hlt">auroral</span> oval) track each other quite well in brightness at these two wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRA..123.3900K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRA..123.3900K"><span>Measurements of Ion-Neutral Coupling in the <span class="hlt">Auroral</span> F Region in Response to Increases in Particle Precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kiene, A.; Bristow, W. A.; Conde, M. G.; Hampton, D. L.</p> <p>2018-05-01</p> <p>Neutral winds are a key factor in the dynamics of the ionosphere-thermosphere system. Previous observations have shown that neutral and ion flows are strongly coupled during periods of <span class="hlt">auroral</span> activity when ion drag forcing can become the dominant force driving neutral wind flow. This is primarily due to increases in ion density due to enhanced particle precipitation as well as associated increases the strength of the electric fields that drive ion motions. Due to this strong coupling, numerical simulations of neutral dynamics have difficulty reproducing neutral wind observations when they are driven by modeled precipitation and modeled convection. It is therefore desirable whenever possible to have concurrent coincident measurements of <span class="hlt">auroral</span> precipitation and ion convection. Recent advancements in high-resolution fitting of Super Dual <span class="hlt">Auroral</span> Radar Network ion convection data have enabled the generation of steady maps of ion drifts over Alaska, coinciding with several optics sites. The Super Dual <span class="hlt">Auroral</span> Radar Network measurements are compared with scanning Doppler imager neutral wind measurements at similar altitude, providing direct comparisons of ion and neutral velocities over a wide field and for long periods throughout the night. Also present are a digital all-sky imager and a meridian spectrograph, both of which provide measurements of <span class="hlt">auroral</span> intensity on several wavelengths. In this study, we combine these data sets to present three case studies that show significant correlation between increases in F region precipitation and enhancements in ion-neutral coupling in the evening sector. We investigate the time scales over which the coupling takes place and compare our findings to previous measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/803851','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/803851"><span>Comparative Dosimetric Estimates of a 25 <span class="hlt">keV</span> <span class="hlt">Electron</span> Micro-beam with three Monte Carlo Codes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Mainardi, Enrico; Donahue, Richard J.; Blakely, Eleanor A.</p> <p>2002-09-11</p> <p>The calculations presented compare the different performances of the three Monte Carlo codes PENELOPE-1999, MCNP-4C and PITS, for the evaluation of Dose profiles from a 25 <span class="hlt">keV</span> <span class="hlt">electron</span> micro-beam traversing individual cells. The overall model of a cell is a water cylinder equivalent for the three codes but with a different internal scoring geometry: hollow cylinders for PENELOPE and MCNP, whereas spheres are used for the PITS code. A cylindrical cell geometry with scoring volumes with the shape of hollow cylinders was initially selected for PENELOPE and MCNP because of its superior simulation of the actual shape and dimensions ofmore » a cell and for its improved computer-time efficiency if compared to spherical internal volumes. Some of the transfer points and energy transfer that constitute a radiation track may actually fall in the space between spheres, that would be outside the spherical scoring volume. This internal geometry, along with the PENELOPE algorithm, drastically reduced the computer time when using this code if comparing with event-by-event Monte Carlo codes like PITS. This preliminary work has been important to address dosimetric estimates at low <span class="hlt">electron</span> energies. It demonstrates that codes like PENELOPE can be used for Dose evaluation, even with such small geometries and energies involved, which are far below the normal use for which the code was created. Further work (initiated in Summer 2002) is still needed however, to create a user-code for PENELOPE that allows uniform comparison of exact cell geometries, integral volumes and also microdosimetric scoring quantities, a field where track-structure codes like PITS, written for this purpose, are believed to be superior.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950011879&hterms=Frank+Pedersen&qs=N%3D0%26Ntk%3DAuthor-Name%26Ntx%3Dmode%2Bmatchall%26Ntt%3DFrank%2BPedersen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950011879&hterms=Frank+Pedersen&qs=N%3D0%26Ntk%3DAuthor-Name%26Ntx%3Dmode%2Bmatchall%26Ntt%3DFrank%2BPedersen"><span>Magnetospheric electric fields and <span class="hlt">auroral</span> oval</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Laakso, Harri; Pedersen, Arne; Craven, John D.; Frank, L. A.</p> <p>1992-01-01</p> <p>DC electric field variations in a synchronous orbit (GEOS 2) during four substorms in the time sector 19 to 01 LT were investigated. Simultaneously, the imaging photometer on board DE 1 provided <span class="hlt">auroral</span> images that are also utilized. Substorm onset is defined here as a sudden appearance of large electric fields. During the growth phase, the orientation of the electric field begins to oscillate some 30 min prior to onset. About 10 min before the onset GEOS 2 starts moving into a more tenuous plasma, probably due to a thinning of the current sheet. The onset is followed by a period of 10 to 15 min during which large electric fields occur. This interval can be divided into two intervals. During the first interval, which lasts 4 to 8 min, very large fields of 8 to 20 mV/m are observed, while the second interval contains relatively large fields (2 to 5 mV/m). A few min after the onset, the spacecraft returns to a plasma region of higher <span class="hlt">electron</span> fluxes which are usually larger than before substorm. Some 30 min after onset, enhanced activity, lasting about 10 min, appears in the electric field. One of the events selected offers a good opportunity to study the formation and development of the Westward Traveling Surge (WST). During the traversal of the leading edge of the WTS (approximately 8 min) a stable wave mode at 5.7 mHz is detected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850014173','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850014173"><span><span class="hlt">Auroral</span>-polar cap environment and its impact on spacecraft plasma interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Garrett, H. B.</p> <p>1985-01-01</p> <p>The high density of the plasma at shuttle altitude is likely to increase greatly the possibility of arcing and shorting of exposed high voltage surfaces. For military missions over the polar caps and through the auoroal zones, the added hazards of high energy <span class="hlt">auroral</span> particle fluxes or solar flares will further increase the hazard to shuttle, its crew, and its mission. A review of the role that the <span class="hlt">auroral</span> and polar cap environment play in causing these interactions was conducted. A simple, though comprehensive attempt at modelling the shuttle environment at 400 km will be described that can be used to evaluate the importance of the interactions. The results of this evaluation are then used to define areas where adequate environmental measurements will be necessary if a true spacecraft interactions technology is to be developed for the shuttle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920061065&hterms=MOOS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMOOS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920061065&hterms=MOOS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMOOS"><span>Jovian ultraviolet <span class="hlt">auroral</span> activity, 1981-1991</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Livengood, T. A.; Moos, H. W.; Ballester, G. E.; Prange, R. M.</p> <p>1992-01-01</p> <p>IUE observations of H2 UV emissions for the 1981-1991 period are presently used to investigate the <span class="hlt">auroral</span> brightness distribution on the surface of Jupiter. The brightness, which is diagnostic of energy input to the atmosphere as well as of magnetospheric processes, is determined by comparing model-predicted brightnesses against empirical ones. The north and south aurorae appear to be correlated in brightness and in variations of the longitude of peak brightness. There are strong fluctuations in all the parameters of the brightness distribution on much shorter time scales than those of solar maximum-minimum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhyB..403.4309V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhyB..403.4309V"><span>Compton scattering study of <span class="hlt">electron</span> momentum distribution in lithium fluoride using 662 <span class="hlt">keV</span> gamma radiations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vijayakumar, R.; Shivaramu; Ramamurthy, N.; Ford, M. J.</p> <p>2008-12-01</p> <p>Here we report the first ever 137Cs Compton spectroscopy study of lithium fluoride. The spherical average Compton profiles of lithium fluoride are deduced from Compton scattering measurements on poly crystalline sample at gamma ray energy of 662 <span class="hlt">keV</span>. To compare the experimental data, we have computed the spherical average Compton profiles using self-consistent Hartree-Fock wave functions employed on linear combination of atomic orbital (HF-LCAO) approximation. The directional Compton profiles and their anisotropic effects are also calculated using the same HF-LCAO approximation. The experimental spherical average profiles are found to be in good agreement with the corresponding HF-LCAO calculations and in qualitative agreement with Hartree-Fock free atom values. The present experimental isotropic and calculated directional profiles are also compared with the available experimental isotropic and directional Compton profiles using 59.54 and 159 <span class="hlt">keV</span> γ-rays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2351L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2351L"><span>Anomalous <span class="hlt">electron</span> heating effects on the E region ionosphere in TIEGCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Jing; Wang, Wenbin; Oppenheim, Meers; Dimant, Yakov; Wiltberger, Michael; Merkin, Slava</p> <p>2016-03-01</p> <p>We have recently implemented a new module that includes both the anomalous <span class="hlt">electron</span> heating and the <span class="hlt">electron</span>-neutral cooling rate correction associated with the Farley-Buneman Instability (FBI) in the thermosphere-ionosphere electrodynamics global circulation model (TIEGCM). This implementation provides, for the first time, a modeling capability to describe macroscopic effects of the FBI on the ionosphere and thermosphere in the context of a first-principle, self-consistent model. The added heating sources primarily operate between 100 and 130 km altitude, and their magnitudes often exceed <span class="hlt">auroral</span> precipitation heating in the TIEGCM. The induced changes in E region <span class="hlt">electron</span> temperature in the <span class="hlt">auroral</span> oval and polar cap by the FBI are remarkable with a maximum Te approaching 2200 K. This is about 4 times larger than the TIEGCM run without FBI heating. This investigation demonstrates how researchers can add the important effects of the FBI to magnetosphere-ionosphere-thermosphere models and simulators.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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