Discrete and broadband electron acceleration in Jupiter's powerful aurora.

PubMed

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

2017-09-06

The most intense auroral emissions from Earth's polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of electrons 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 electrons (in the case of diffuse aurora) or by the turbulent or stochastic downward acceleration of electrons 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 auroral process. However, preliminary in situ measurements of Jupiter's auroral regions yielded no evidence of such a process. Here we report observations of distinct, high-energy, downward, discrete electron acceleration in Jupiter's auroral 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.

Non-equilibrium calculations of atmospheric processes initiated by electron impact.

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.

2007-05-01

Electron impact in the atmosphere produces ionisation, dissociation, electronic excitation and vibrational excitation of atoms and molecules. The products can then take part in chemical reactions, recombination with electrons, or radiative or collisional deactivation. While most such processes are fast, some longer--lived species do not reach equilibrium. The electron source (photoelectrons or auroral electrons) 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 electron density and its dependence on vibrationally excited N2, predictions of nitric oxide density, and detailed processes during short duration auroral events.

Magnetospheric electrons

NASA Technical Reports Server (NTRS)

Coroniti, F. V.; Thorne, R. M.

1972-01-01

Coupling of source, transport, and sink processes produces a fairly accurate model for the macroscopic structure and dynamics of magnetospheric electrons. Auroral electrons 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 electrons 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.

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.

Effects of a parallel electric field and the geomagnetic field in the topside ionosphere on auroral and photoelectron energy distributions

NASA Technical Reports Server (NTRS)

Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

1993-01-01

The consequences of electric field acceleration and an inhomogeneous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one-dimensional, steady state electron 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 electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron 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 electron 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 electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogeneous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

Effects of a Parallel Electric Field and the Geomagnetic Field in the Topside Ionosphere on Auroral and Photoelectron Energy Distributions

NASA Technical Reports Server (NTRS)

Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

1993-01-01

The consequences of electric field acceleration and an inhomogencous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one- dimensional, steady state electron 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 electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron 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 electron 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 electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogencous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

Superthermal Electron Magnetosphere-Ionosphere Coupling in the Diffuse Aurora in the Presence of ECH Waves

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Tripathi, A. K.; Singhal, R. P.; Himwich, Elizabeth; Glocer, A.; Sibeck, D. G.

2015-01-01

There are two main theories for the origin of the diffuse auroral electron precipitation: first, pitch angle scattering by electrostatic electron cyclotron harmonic (ECH) waves, and second, by whistler mode waves. Precipitating electrons initially injected from the plasma sheet to the loss cone via wave-particle interaction processes degrade in the atmosphere toward lower energies and produce secondary electrons via impact ionization of the neutral atmosphere. These secondary electrons can escape back to the magnetosphere, become trapped on closed magnetic field lines, and deposit their energy back to the inner magnetosphere. ECH and whistler mode waves can also move electrons in the opposite direction, from the loss cone into the trap zone, if the source of such electrons exists in conjugate ionospheres located at the same field lines as the trapped magnetospheric electron population. Such a situation exists in the simulation scenario of superthermal electron energy interplay in the region of diffuse aurora presented and discussed by Khazanov et al. (2014) and will be quantified in this paper by taking into account the interaction of secondary electrons with ECH waves.

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.

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.

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.

Physical Processes for Driving Ionospheric Outflows in Global Simulations

NASA Technical Reports Server (NTRS)

Moore, Thomas Earle; Strangeway, Robert J.

2009-01-01

We review and assess the importance of processes thought to drive ionospheric outflows, linking them as appropriate to the solar wind and interplanetary magnetic field, and to the spatial and temporal distribution of their magnetospheric internal responses. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitating particles. Observations and simulations show that solar wind energy dissipation into the atmosphere is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma, neutral gas and by extension, the entire body " We assess the Importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multispecies global simulation codes. We complete 'he survey with an assessment of outstanding obstacles to this objective.

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.

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-aligned potential difference, particularly during active time (AE > 100 nT). On the other hand, in the dusk side outer magnetosphere (source of the region 1), electron density and temperature are small, thus the thermal current is much smaller than the typical auroral current suggested by Iijima and Potemra (JGR, 1976). From this result, we suppose that electron acceleration is necessary on the dusk side region 1 upward field-aligned current. Our preliminary result, however, does not consider contamination of the radiation belt particles into the ESA data that is apparent inside 9 Re. In the presentation, we show the results with removal of the radiation belt particle contamination.

Imaging Magnetospheric Boundries at Ionospheric Heights

NASA Astrophysics Data System (ADS)

Baumgardner, J.; Nottingham, D.; Wroten, J.; Mendillo, M.

2001-12-01

Stable auroral red (SAR) arcs are excited by a downward heat flux within a narrow range of fluxtubes that define the plasmapause-ring current interaction region. Ambient F-region electrons near and above the peak height (300-500 km) are heated and collisionally excite atomic oxygen to the O(1D) state, thereby emitting 6300 A photons. At the same time, the diffuse aurora at 6300 A is excited by the precipitation of plasma sheet electrons into the lower thermosphere, exciting O(1D) to emit near 200 km. An all-sky imaging system operating at a sub-auroral site (e.g., at Millstone Hill) can readily record the SAR arc centroid location and the equatorial edge of the diffuse aurora in the same 6300 A image. We have analyzed 75 such cases showing where both stuctures occur in the ionosphere and then conducted field-line mapping to define the L-shell domains of origin in the equatorial plane of the inner magnetosphere (L ~ 2.5 - 4). To within the measurement and mapping accuracies, both boundaries coincide, i.e., the inner edge of the plasma sheet essentially falls along the plasmapause. Since the O(1D) 6300 A emission corresponds to ~2 ev of excitation by magnetospheric processes, this technique defines ELENA (Extremely Low Energetic Neutral Atom) imaging of magnetospheric structures.

Polar Plasma Wave Investigation Data Analysis in the Extended Mission

NASA Technical Reports Server (NTRS)

Gurnett, Donald A.; Menietti, J. D.

2003-01-01

The low latitude boundary layer (LLBL) is a region where solar wind momentum and energy is transferred to the magnetosphere. Enhanced "broadband" electric plasma waves from less than 5 Hz to l0(exp 5) Hz and magnetic waves from less than 5 Hz to the electron cyclotron frequency are characteristic of the LLBL. Analyses of Polar plasma waves show that these "broadband" waves are actually discrete electrostatic and electromagnetic modes as well as solitary bipolar pulses (electron holes). It is noted that all wave modes can be generated by approx. 100 eV to approx. 10 keV auroral electrons and protons. We will review wave-particle interactions, with focus on cross- diffusion rates and the contributions of such interactions toward the formation of the boundary layer. In summary, we will present a scenario where the global solar wind-magnetosphere interaction is responsible for the auroral zone particle beams, and hence for the generation of plasma waves and the formation of the boundary layer. It is speculated that all planetary magnetospheres will have boundary layers and they will be characterized by similar currents and plasma wave modes.

Polar Plasma Wave Investigation Data Analysis in the Extended Mission

NASA Technical Reports Server (NTRS)

Gurnett, Donald A.

2004-01-01

The low latitude boundary layer (LLBL) is a region where solar wind momentum and energy is transferred to the magnetosphere. Enhanced "broadband" electric plasma waves from less than 5 Hz to 10(exp 5) Hz and magnetic waves from less than 5 Hz to the electron cyclotron frequency are characteristic of the LLBL. Analyses of Polar plasma waves show that these "broadband" waves are actually discrete electrostatic and electromagnetic modes as well as solitary bipolar pulses (electron holes). It is noted that all wave modes can be generated by approx. 100 eV to approx. 10 keV auroral electrons and protons. We will review wave-particle interactions, with focus on cross-diffusion rates and the contributions of such interactions toward the formation of the boundary layer. In summary, we will present a scenario where the global solar wind-magnetosphere interaction is responsible for the auroral zone particle beams, and hence for the generation of plasma waves and the formation of the boundary layer. It is speculated that all planetary magnetospheres will have boundary layers and they will be characterized by similar currents and plasma wave modes.

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.

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

Small-Scale Features in Pulsating Aurora

NASA Technical Reports Server (NTRS)

Jones, Sarah; Jaynes, Allison N.; Knudsen, David J.; Trondsen, Trond; Lessard, Marc

2011-01-01

A field study was conducted from March 12-16, 2002 using a narrow-field intensified CCD camera installed at Churchill, Manitoba. The camera was oriented along the local magnetic zenith where small-scale black auroral forms are often visible. This analysis focuses on such forms occurring within a region of pulsating aurora. The observations show black forms with irregular shape and nonuniform drift with respect to the relatively stationary pulsating patches. The pulsating patches occur within a diffuse auroral background as a modulation of the auroral brightness in a localized region. The images analyzed show a decrease in the brightness of the diffuse background in the region of the pulsating patch at the beginning of the offphase of the modulation. Throughout the off phase the brightness of the diffuse aurora gradually increases back to the average intensity. The time constant for this increase is measured as the first step toward determining the physical process.

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.

Wave-particle interactions on the FAST satellite

NASA Technical Reports Server (NTRS)

Temerin, M. A.; Carlson, C. W.; Cattell, C. A.; Ergun, R. E.; Mcfadden, J. P.

1990-01-01

NASA's Fast Auroral Snapshot, or 'FAST' satellite, scheduled for launch in 1993, will investigate the plasma physics of the low altitude auroral zone from a 3500-km apogee polar orbit. FAST will give attention to wave, double-layer, and soliton production processes due to electrons and ions, as well as to wave-wave interactions, and the acceleration of electrons and ions by waves and electric fields. FAST will employ an intelligent data-handling system capacle of data acquisition at rates of up to 1 Mb/sec, in addition to a 1-Gbit solid-state memory. The data need be gathered for only a few minutes during passes through the auroral zone, since the most interesting auroral phenomena occur in such narrow regions as auroral arcs, electrostatic shocks, and superthermal electron bursts.

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.

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.

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.

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 processes related to the EEP and its effects on the atmosphere through changes in the minor components.

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.

Optical observations of Magnetosphere-Ionosphere coupling: Inter-hemispheric electron reflections within pulsating aurora

NASA Astrophysics Data System (ADS)

Samara, M.; Michell, R.; Khazanov, G. V.; Grubbs, G. A., II

2017-12-01

Magnetosphere-Ionosphere coupling is exhibited in reflected primary and secondary electrons which constitute the second step in the formation of the total precipitating electron distribution. While they have largely been missing from the current theoretical studies of particle precipitation, ground based observations point to the existence of a reflected electron population. We present evidence that pulsating aurora is caused by electrons bouncing back and forth between the two hemispheres. This means that these electrons are responsible for some of the total light in the aurora, a possibility that has largely been ignored in theoretical models. Pulsating auroral events imaged optically at high time resolution present direct observational evidence in agreement with the inter-hemispheric electron bouncing predicted by the SuperThermal Electron Trans-port (STET) model. Immediately following each of the `pulsation-on' times are equally spaced, and subsequently fainter pulsations, which can be explained by the primary precipitating electrons reflecting upwards from the ionosphere, traveling to the opposite hemisphere, and reflecting upwards again. The high time-resolution of these data, combined with the short duration of the `pulsation-on' time ( 1 s) and the relatively long spacing between pulsations ( 6 to 9 s) made it possible to observe the faint optical pulses caused by the reflected electrons coming from the opposite hemisphere. These results are significant and have broad implications because they highlight that the formation of the auroral electron distributions within regions of diffuse and pulsating aurora contain contributions from reflected primary and secondary electrons. These processes can ultimately lead to larger fluxes than expected when considering only the primary injection of magnetospheric electrons.

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.

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.

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.

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.

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 from the poleward edge of the auroral zone is the primary field-aligned current region which results in the classical field- aligned acceleration associated with the auroral zone (electrons earthward and ion beams tailward). During times of high magnetic activity, high-energy ion beams originating from the magnetotail are observed within, and overlapping, the regions of primary and return field-aligned current. Along the field lines where the high-energy magnetotail ion beams are located, field-aligned acceleration can occur in the auroral zone leading to precipitating electrons and upwelling ionospheric ion beams. Field-aligned currents are present during both quiet and active times, while the Alfven waves and magnetotail ion beams were observed only during more magnetically active events.

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.

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.

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.

U.S. national report to the International Union of Geodesy and Geophysics

NASA Technical Reports Server (NTRS)

Gorney, D. J.

1987-01-01

This paper highlights progress by U.S. authors during 1983-1986 in the broad area of auroral research. Atmospheric emissions and their use as a tool for remote-sensing the dynamics, energetics, and effects of auroral activity is a subject which is emphasized here because of the vast progress made in this area on both observational and theoretical fronts. The evolution of primary auroral electrons, the acceleration of auroral ions, small-scale electric fields, auroral kilometric radiation, auroral empirical models and activity indices are also reviewed. An extensive bibliography is supplied.

US national report to the International Union of Geodesy and Geophysics

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

Gorney, D.J.

1987-04-01

This paper highlights progress by U.S. authors during 1983-1986 in the broad area of auroral research. Atmospheric emissions and their use as a tool for remote-sensing the dynamics, energetics, and effects of auroral activity is a subject which is emphasized here because of the vast progress made in this area on both observational and theoretical fronts. The evolution of primary auroral electrons, the acceleration of auroral ions, small-scale electric fields, auroral kilometric radiation, auroral empirical models and activity indices are also reviewed. An extensive bibliography is supplied.

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.

Direct comparison between satellite electric field measurements and the visual aurora

NASA Technical Reports Server (NTRS)

Swift, D. W.; Gurnett, D. A.

1973-01-01

Electric field data from two passes of the Injun 5 satellite, one corresponding to magnetically quiet conditions and one corresponding to substorm conditions, are compared with simultaneous all-sky-camera data from College, Alaska. In each case, a significant deviation of the electric field from the expected V x B field (where V is the satellite velocity) was evident and a distinct electric field reversal could be identified. In the region of substantial electric field equatorward of the electric field reversal a diffuse auroral arc was observed during the magnetically quiet pass and auroral patches were observed during the substorm pass. The motion of the auroral patches was consistent with the general direction and magnitude of the E x B drift computed from the satellite electric field measurements. In the substorm case the electric field reversal occurred very near a discrete auroral arc at the poleward side of the diffuse arcs and patches. Comparison of the quiet time and substorm cases suggests that the convection electric field penetrates deeper into the magnetosphere during a substorm.

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.

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.

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.

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.

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.

Role of electronic excited N2 in vibrational excitation of the N2 ground state at high latitudes

NASA Astrophysics Data System (ADS)

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

2006-09-01

Vibrationally excited N2 is important in determining the ionospheric electron density and has also been proposed to play a role in the production of NO in disturbed atmospheres. We report here predictions of the absolute vibrational distributions in the ground electronic state of N2 produced by electron impact excitation, at noon and midnight under quiet geomagnetic conditions and disturbed conditions corresponding to the aurora IBCII+ and IBCIII+ at 60°N latitude and 0° longitude, at altitudes between 130 and 350 km. These predictions were obtained from a model which includes thermal excitation and direct electron impact excitation of the vibrational levels of the N2 ground state and its excited electronic states; radiative cascade from all excited electronic states to all vibrational levels of the ground electronic state; quenching by O, O2, and N2; molecular and ambipolar diffusion; and the dominant chemical reactions. Results from this study show that for both aurora and daytime electron environments: (1) cascade from the higher electronic states of N2 determines the population of the higher vibrational levels in the N2 ground state and (2) the effective ground state vibrational temperature for levels greater than 4 in N2 is predicted to be in the range 4000-13000 K for altitudes greater than 200 km. Correspondingly, the associated enhancement factor for the O+ reaction with vibrationally excited N2 to produce NO+ is predicted to increase with increasing altitude (up to a maximum at a height which increases with auroral strength) for both aurora and daytime environments and to increase with increasing auroral strength. The contribution of the cascade from the excited electronic states was evaluated and found to be relatively minor compared to the direct excitation process.

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.

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.

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.

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.

Kilometric radiation power flux dependence on area of discrete aurora

NASA Technical Reports Server (NTRS)

Saflekos, N. A.; Burch, J. L.; Gurnett, D. A.; Anderson, R. R.; Sheehan, R. E.

1989-01-01

Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

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.

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

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.

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.

Discovery of Diffuse Hard X-ray Emission associated with Jupiter

NASA Astrophysics Data System (ADS)

Ezoe, Y.; Miyoshi, Y.; Ishikawa, K.; Ohashi, T.; Terada, N.; Uchiyama, Y.; Negoro, H.

2009-12-01

Our discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter is reported. Recent Chandra and XMM-Newton observations revealed several types of X-rays in the vicinity of Jupiter such as auroral and disk emission from Jupiter and faint diffuse X-rays from the Io Plasma Torus (see Bhardwaj et al. 2007 for review). To investigate possible diffuse hard X-ray emission around Jupiter with the highest sensitivity, we conducted data analysis of Suzaku XIS observations of Jupiter on Feb 2006. After removing satellite and planetary orbital motions, we detected a significant diffuse X-ray emission extending to ~6 x 3 arcmin with the 1-5 keV X-ray luminosity of ~3e15 erg/s. The emitting region very well coincided with the Jupiter's radiation belts. The 1-5 keV X-ray spectrum was represented by a simple power law model with a photon index of 1.4. Such a flat continuum strongly suggests non-thermal origin. Although such an emission can be originated from multiple background point sources, its possibility is quite low. We hence examined three mechanisms, assuming that the emission is truly diffuse: bremsstrahlung by keV electrons, synchrotron emission by TeV electrons, and inverse Compton scattering of solar photons by MeV electrons. The former two can be rejected because of the X-ray spectral shape and implausible existence of TeV electrons around Jupiter, respectively. The last possibility was found to be possible because tens MeV electrons, which have been confirmed in inner radiation belts (Bolton et al. 2002), can kick solar photons to the keV energy range and provide a simple power-law continuum. We estimated an average electron density from the X-ray luminosity assuming the oblate spheroid shaped emitting region with 8 x 8 x 4 Jovian radii. The necessary density was 0.02 1/cm3 for 50 MeV electrons. Hence, our results may suggest a new particle acceleration phenomenon around Jupiter.

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.

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.

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.

Artificial auroras in the upper atmosphere. I - Electron beam injections

NASA Technical Reports Server (NTRS)

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.

1993-01-01

The Atlas-1 Spacelab payload's Space Experiments with Particle Accelerators generated artificial electron beams for the stimulation of auroral emissions at southern auroral 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 auroral 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.

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.

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.

THE RELATIONSHIP BETWEEN THE SEPTEMBER 2017 MARS GLOBAL AURORA EVENT AND CRUSTAL MAGNETIC FIELDS

NASA Astrophysics Data System (ADS)

Nasr, Camella-Rosa; Schneider, Nick; Connour, Kyle; Jain, Sonal; Deighan, Justin; Jakosky, Bruce; MAVEN/IUVS Team

2018-01-01

In September 2017, the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft observed global aurora on Mars caused by a surprisingly strong solar energetic particle event. Widespread “diffuse aurora” have previously been detected on Mars through more limited observations (Schneider et al., Science 350, (2015); DOI: 10.1126/science.aad0313), but recent observations established complete coverage of the observable portion of Mars’ nightside. The aurora was global due to Mars’s lack of a global magnetic field, which allowed energetic electrons from the Sun to directly precipitate into the atmosphere. On September 11th, IUVS detected aurora more than 25 times brighter than any prior IUVS observation, with high SNR detections of aurora at the limb and against the disk of the planet. Fainter auroral emission was seen around the nightside limb over 13 orbits spanning nearly 3 days.On September 14th, during the declining phase of the event, faint linear features and patches were detected by the spacecraft, which were higher than the noise floor, with a similar spatial distribution to “discrete aurora” patches observed on Mars by the SPICAM instrument on the Mars Express spacecraft (Bertaux et al., Nature 435, doi :10.1038/nature03603). Discrete aurora occur near areas of the crust affected by the magnetism left over from Mars’ once-strong dipole field. Emission is limited to regions of the crustal magnetic field where the field lines are likely to be open to solar wind interactions. Those regions are concentrated in Mars’ southern hemisphere centered on 180 degrees east longitude.We studied the localized emissions on 14 September to determine whether there might be a connection between the observed diffuse aurora event and discrete auroral processes. First, we investigated the localized emissions to confirm that the observed signal was consistent with expected auroral spectra. Second, their locations were projected on a map of the crustal magnetic fields to determine if they occurred near open magnetic field lines. We will report on the results of these two studies, and the ramifications for Mars auroral processes.

A search for thermospheric composition perturbations due to vertical winds

NASA Astrophysics Data System (ADS)

Krynicki, Matthew P.

The thermosphere is generally in hydrostatic equilibrium, with winds blowing horizontally along stratified constant-pressure surfaces, driven by the dayside-to-nightside pressure gradient. A marked change in this paradigm resulted after Spencer et al. [1976] reported vertical wind measurements of 80 m·s-1 from analyses of AE-C satellite data. It is now established that the thermosphere routinely supports large-magnitude (˜30-150 m·s-1) vertical winds at auroral latitudes. These vertical winds represent significant departure from hydrostatic and diffusive equilibrium, altering locally---and potentially globally---the thermosphere's and ionosphere's composition, chemistry, thermodynamics and energy budget. Because of their localized nature, large-magnitude vertical wind effects are not entirely known. This thesis presents ground-based Fabry-Perot Spectrometer OI(630.0)-nm observations of upper-thermospheric vertical winds obtained at Inuvik, NT, Canada and Poker Flat, AK. The wind measurements are compared with vertical displacement estimates at ˜104 km2 horizontal spatial scales determined from a new modification to the electron transport code of Lummerzheim and Lilensten [1994] as applied to FUV-wavelength observations by POLAR spacecraft's Ultraviolet Imager [Torr et al. , 1995]. The modification, referred to as the column shift, simulates vertical wind effects such as neutral transport and disruption of diffusive equilibrium by vertically displacing the Hedin [1991] MSIS-90 [O2]/[N2] and [O]/([N2]+[O2]) mixing ratios and subsequently redistributing the O, O2, and N 2 densities used in the transport code. Column shift estimates are inferred from comparisons of UVI OI(135.6)-nm auroral observations to their corresponding modeled emission. The modeled OI(135.6)-nm brightness is determined from the modeled thermospheric response to electron precipitation and estimations of the energy flux and characteristic energy of the precipitation, which are inferred from UVI-observed Lyman-Birge-Hopfield N2 emissions in two wavelength ranges. Two-dimensional column shift maps identify the spatial morphology of thermospheric composition perturbations associated with auroral forms relative to the model thermosphere. Case-study examples and statistical analyses of the column shift data sets indicate that column shifts can be attributed to vertical winds. Unanticipated limitations associated with modeling of the OI(135.6)-nm auroral emission make absolute column shift estimates indeterminate. Insufficient knowledge of thermospheric air-parcel time histories hinders interpretations of point-to-point time series comparisons between column shifts and vertical winds.

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.

The Aurora, Magnetosphere, and the IGY

NASA Astrophysics Data System (ADS)

McKim Malville, J.

2007-12-01

This retrospective of auroral research during the IGY will be from the perspective of the auroral observers in the Antarctic from 1956-58. The IGY served as a watershed divide in our understanding of auroral physics. Prior to the IGY the role of "solar corpuscular radiation” in exciting auroral radiation was the pre-eminent research question. The mechanisms for the acceleration of solar protons and electrons had not been resolved, nor had the role of plasma instabilities been envisioned. The spectroscopic research program during the IGY was dominated by the work of Aden Meinel and Joseph W. Chamberlain at Yerkes Observatory. The dynamics of precipitating solar protons into a dilute gas was a major research focus. The changes brought about by the discoveries of the radiation belts, the solar wind, and the magnetosphere resulted in a remarkable transformation and a paradigm shift in our understanding of the physics of the aurora. Antarctic observations during the IGY revealed the auroral oval, which is a signature of radiation belts distorted by the solar wind. High auroral rays could be explained by pitch angle distributions of trapped electrons. Sudden accelerations of electrons, resulting in red lower borders of aurora deep in the atmosphere, revealed the serious deficiencies of available theory. Whistlers, first detected in the Antarctic at Ellsworth Station in 1957, proved to be valuable probes of the magnetosphere.

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.

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.

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.

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.

Pulsating midmorning auroral arcs, filamentation of a mixing region in a flank boundary layer, and ULF waves observed during a Polar-Svalbard conjunction

NASA Astrophysics Data System (ADS)

Farrugia, C. J.; Sandholt, P. E.; Maynard, N. C.; Burke, W. J.; Scudder, J. D.; Ober, D. M.; Moen, J.; Russell, C. T.

2000-12-01

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 Auroral 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 electron and ion fluxes are enhanced. These filaments are associated with field-aligned current structures embedded within the large-scale region 1 (R1) current. Ground auroral 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 auroral arcs correlate with Pc 5 pulsations and are probably related to modulations in the interplanetary electric field. The auroral 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 auroral 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 the pulsating diffuse aurora when the IMF went to an approximately Parker spiral orientation and the ground stations had rotated into the MLT sector of cusp emissions.

Strong Ionospheric Electron Heating Associated With Pulsating Auroras - A Swarm Survey

NASA Astrophysics Data System (ADS)

Liang, J.; Yang, B.; Burchill, J. K.; Donovan, E.; Knudsen, D. J.

2016-12-01

A pulsating aurora is a repetitive modulation of auroral luminosity with periods typically of the order of 1-30 sec. It is often observed in the equatorward portion of the auroral oval. While it is generally recognized that the ultimate source of the pulsating auroral precipitation comes from energetic electrons 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 (electron temperature, plasma density and field-aligned current etc.) of pulsating auroras using Swarm satellite data. Via the survey we repeatedly identify a strong electron temperature enhancement associated with the pulsating aurora. On average, the electron 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 auroral patch when the patch is "on" during the traversal of satellites [Gillies et al., 2015], and the electron 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 auroral 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 strong electron heating associated with the pulsating aurora, including the Joule heating related to the field-aligned current and to the structured electric field, the backscattered secondary electrons led by the impact of pulsating auroral precipitation, and the vertical conductive heat transport.

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.

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.

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

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.

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR

NASA Technical Reports Server (NTRS)

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.;

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.

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.

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.

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

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.

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.

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.

Electron Collisions in our Atmosphere — How the Microscopic Drives the Macroscopic

NASA Astrophysics Data System (ADS)

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

2005-05-01

Recent measurements of low energy, absolute electron scattering cross sections for vibrational excitation of NO have been used to update the cross set used for modeling atmospheric auroral 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 electron-driven processes play an important role in the infrared (˜5 um) auroral emissions from the NO molecule.

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.

Nonequilibrium calculations of the role of electron impact in the production of NO and its emissions

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.

2009-04-01

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 electron impact excitation to the NO density and the sensitivity of this process to the electron impact cross sections. The results are compared with satellite measurements of NO densities in equatorial and auroral high-latitude conditions and with rocket measurements of infrared emissions in auroral conditions. Particular findings are that electron impact excitation of N2 makes a significant contribution to the NO density at altitudes around 105 km and to auroral 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.

Development of a Geomagnetic Storm Correction to the International Reference Ionosphere E-Region Electron Densities Using TIMED/SABER Observations

NASA Technical Reports Server (NTRS)

Mertens, C. J.; Xu, X.; Fernandez, J. R.; Bilitza, D.; Russell, J. M., III; Mlynczak, M. G.

2009-01-01

Auroral 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 electron 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 auroral oval region. The STORM-E predictions of E-region electron densities are compared to incoherent scatter radar electron density measurements during the Halloween 2003 storm events. Future STORM-E updates will extend the model outside the auroral oval.

Resonant scattering of energetic electrons in the outer radiation belt by HAARP-induced ELF/VLF waves

NASA Astrophysics Data System (ADS)

Chang, Shanshan; Zhu, Zhengping; Ni, Binbin; Cao, Xing; Luo, Weihua

2016-10-01

Several extremely low-frequency (ELF)/very low-frequency (VLF) wave generation experiments have been performed successfully at High-Frequency Active Auroral Research Program (HAARP) heating facility and the artificial ELF/VLF signals can leak into the outer radiation belt and contribute to resonant interactions with energetic electrons. Based on the artificial wave properties revealed by many of in situ observations, we implement test particle simulations to evaluate the effects of energetic electron resonant scattering driven by the HAARP-induced ELF/VLF waves. The results indicate that for both single-frequency/monotonic wave and multi-frequency/broadband waves, the behavior of each electron is stochastic while the averaged diffusion effect exhibits temporal linearity in the wave-particle interaction process. The computed local diffusion coefficients show that, the local pitch-angle scattering due to HARRP-induced single-frequency ELF/VLF whistlers with an amplitude of ∼10 pT can be intense near the loss cone with a rate of ∼10-2 rad2 s-1, suggesting the feasibility of HAARP-induced ELF/VLF waves for removal of outer radiation belt energetic electrons. In contrast, the energy diffusion of energetic electrons is relatively weak, which confirms that pitch-angle scattering by artificial ELF/VLF waves can dominantly lead to the precipitation of energetic electrons. Moreover, diffusion rates of the discrete, broadband waves, with the same amplitude of each discrete frequency as the monotonic waves, can be much larger, which suggests that it is feasible to trigger a reasonable broadband wave instead of the monotonic wave to achieve better performance of controlled precipitation of energetic electrons. Moreover, our test particle scattering simulation show good agreement with the predictions of the quasi-linear theory, confirming that both methods are applied to evaluate the effects of resonant interactions between radiation belt electrons and artificially generated discrete ELF/VLF waves.

High Altitude Plasma Instrument (HAPI) data analysis

NASA Technical Reports Server (NTRS)

Burch, J. L.

1994-01-01

The objectives of the Dynamics Explorer mission are to investigate the coupling of energy, mass, and momentum among the earth's magnetosphere, ionosphere, and upper atmosphere. At launch, on August 3, 1981, DE-1 was placed into an elliptical polar orbit having an apogee of 23,130 km to allow global auroral imaging and crossings of auroral field lines at altitudes of several thousand kilometers. At the same time DE-2 was placed into a polar orbit, coplanar with that of DE-1 but with a perigee altitude low enough (309 km) for neutral measurements and an apogee altitude of 1012 km. The DE-1 High Altitude Plasma Instrument (HAPI) provided data on low and medium energy electrons and ions from August 13, 1981 until December 1, 1981, when a high-voltage failure occured. Analysis of HAPI data for the time period of this contract has produced new results on the source mechanisms for electron conical distributions, particle acceleration phenomena in auroral acceleration regions, Birkeland currents throughout the nightside auroral regions, the source region for auroral kilometric radiation (AKR), and plasma injection phenomena in the polar cusp.

Mesospheric Odd Nitrogen Enhancements During Relativistic Electron Precipitation Events

NASA Technical Reports Server (NTRS)

Aikin, A. C.; Smith, H. J. P.

1999-01-01

The behavior of mesospheric odd nitrogen species during and following relativistic and diffuse auroral precipitation events is simulated, Below 75 km nitric oxide is enhanced in proportion to the ion pair production function associated with the electron precipitation and the length of the event. Nitrogen dioxide and nitric acid are also enhanced. At 65 km the percentage of odd nitrogen for N is 0.1%, HNO3 is 1.6%, NO2 is 15%, and NO is 83.3%. Between 75 and 85 km NO is depleted during particle events due to the faster destruction of NO by N relative to the production of NO by N reacting with O2. Recovery of NO depends on transport from the lower thermosphere, where NO is produced in abundant amounts during particle events.

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 a significant disturbance in the solar wind, involving the generation of an interplanetary shock and the presence of a CME have interacted with the Jovian magnetosphere at about the time of the auroral event. Both arguments suggest that we may have observed for the first time a magnetic storm-type interaction in an outer planet magnetosphere, affecting simultaneously several auroral processes. Conversely, the observed relationship between the level of UV auroral activity and the detection of decameter emission (DAM), if it were a typical feature, might argue in favour of a more direct and permanent association between the auroral processes leading to UV and radio aurorae, possibly related to 'discrete-arc'-like activity and electron precipitation.

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.

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.

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.

The Martian diffuse aurora: Monte Carlo simulations and comparison with IUVS-MAVEN observations

NASA Astrophysics Data System (ADS)

Gerard, J. C. M. C.; Soret, L.; Schneider, N. M.; Shematovich, V.; Bisikalo, D.; Bougher, S. W.; Jain, S.; Lillis, R. J.; Mitchell, D. L.; Jakosky, B. M.; Deighan, J.; Larson, D. E.

2016-12-01

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar activity on several occasions with the IUVS on board the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and visible auroral emissions for initial electron energies from 0.1 to 200 keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6 nm and the Fox-Duffendack-Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2 nm and CI 156.1 nm and 165.7 nm multiplets. We calculate the nadir and limb intensities of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 100-200 keV produce maximum CO2+ UVD emission near 75 km. We combine SWEA and SEP electron energy spectra measured during diffuse aurora to calculate the volume emission rates and compare with IUVS observations of the emission limb profiles. The strongest predicted emissions are the CO2+ FDB, UVD and the CO Cameron bands. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below 110 km. As a consequence, we show that the CO2+ UVD to the Cameron bands ratio increases at low altitude in the energetic diffuse aurora.

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.

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.

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.

The Effects of Solar Wind Dynamic Pressure Changes on the Substorm Auroras and Energetic Electron Injections on 24 August 2005

NASA Astrophysics Data System (ADS)

Li, L. Y.; Wang, Z. Q.

2018-01-01

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 electron drift loss makes the geosynchronous satellites cannot observe the substorm electron 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 auroral brightness but also cause the entire auroral oval to swing in the day-night direction. However, there is no Pi2 pulsation in the nightside auroral 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 auroral 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 auroral 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 electron injections near geosynchronous orbit.

Alfven Waves Underlying Ionospheric Destabilization: Ground-Based Observations

NASA Astrophysics Data System (ADS)

Hirsch, Michael

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 auroral acceleration region, Alfven waves accelerate electrons up to one-tenth the speed of light via wave-particle interactions. These inertial Alfven wave (IAW) accelerated electrons are imbued with sub-100 meter structure perpendicular to geomagnetic field B. The IAW electric field parallel to B accelerates electrons up to about 10 keV along B. The IAW dispersion relation quantifies the precipitating electron striation observed with high-speed cameras as spatiotemporally dynamic fine structured aurora. A network of tightly synchronized tomographic auroral observatories using model based iterative reconstruction (MBIR) techniques were developed in this dissertation. The TRANSCAR electron penetration model creates a basis set of monoenergetic electron beam eigenprofiles of auroral 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 electron multiplying CCD video stream at order 10 ms cadence yields estimates of electron 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 electron precipitation microstructure. This computer vision structured auroral 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 broadcast FM passive radar. The fusion of data from coherent radar backscatter and optical data at order 10 ms cadence confirms and further quantifies the relation of strong Langmuir turbulence and streaming plasma upflows in the ionosphere with the finest spatiotemporal auroral dynamics associated with IAW acceleration. The software programs developed in this dissertation solve the century-old problem of automatically discriminating finely structured aurora from other forms and pushes the observational wave-particle science frontiers forward.

Localized aurora beyond the auroral oval

NASA Astrophysics Data System (ADS)

Frey, Harald U.

2007-03-01

Aurora is the result of the interaction between precipitating energetic electrons and protons with the upper atmosphere. Viewed from space, it generally occurs in continuous and diffuse ovals of light around the geomagnetic poles. Additionally, there are localized regions of aurora that are unrelated to the ovals and exhibit different morphological, spatial, and temporal properties. Some of these localized aurorae are detached from the oval poleward or equatorward of it. Others are located within the oval and are brighter than the surrounding diffuse aurora. Many of them occur only during preferred solar wind conditions and orientations of the interplanetary magnetic field. This review describes the different localized aurorae and their particle sources in the plasma sheet, at the plasmapause, or at the magnetopause. Their origin is still not completely understood, and the study of aurorae can teach a great deal about their underlying physical processes of reconnection, electrostatic acceleration, or wave-particle interactions.

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 "ghosts" behind the main MF burst emission. These data in will additionally allow us to search for the presence of sub-millisecond wave packets, sometimes quasi-periodic, reported by LaBelle et al. [1997, J. Geophys. Res. 102, 22221]. Finally, a search for frequency dispersion or absence thereof will provide a test of theories which speculate that different frequencies originate at different altitudes in the ionosphere.

Theoretical study of the effect of ionospheric return currents on the electron temperature

NASA Technical Reports Server (NTRS)

Schunk, R. W.; Sojka, J. J.; Bowline, M. D.

1987-01-01

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 auroral electron 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 auroral electron temperatures. The thermoelectric effect exhibits a pronounced solar cycle and seasonal dependence, and its heat transport corresponds to an upward flow of electron energy which can be either a source or sink of electron energy depending on altitude and geophysical conditions.

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.

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.

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 provide E0, the characteristic energy and ɛ, the total flux energy of precipitating electrons. The generator properties are then estimated using the iterative technique validated with data from the DMSP-Cluster conjunction.

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.

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.

A Panchromatic View of Brown Dwarf Aurorae

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

Pineda, J. Sebastian; Hallinan, Gregg; Kao, Melodie M.

Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, andmore » optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like H α , in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral H α emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.« less

A Panchromatic View of Brown Dwarf Aurorae

NASA Astrophysics Data System (ADS)

Pineda, J. Sebastian; Hallinan, Gregg; Kao, Melodie M.

2017-09-01

Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, and optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like Hα, in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral Hα emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.

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

Preliminary JIRAM results from Juno polar observations: 3. Evidence of diffuse methane presence in the Jupiter auroral regions

NASA Astrophysics Data System (ADS)

Moriconi, M. L.; Adriani, A.; Dinelli, B. M.; Fabiano, F.; Altieri, F.; Tosi, F.; Filacchione, G.; Migliorini, A.; Gérard, J. C.; Mura, A.; Grassi, D.; Sindoni, G.; Piccioni, G.; Noschese, R.; Cicchetti, A.; Bolton, S. J.; Connerney, J. E. P.; Atreya, S. K.; Bagenal, F.; Gladstone, G. R.; Hansen, C.; Kurth, W. S.; Levin, S. M.; Mauk, B. H.; McComas, D. J.; Turrini, D.; Stefani, S.; Olivieri, A.; Amoroso, M.

2017-05-01

Throughout the first orbit of the NASA Juno mission around Jupiter, the Jupiter InfraRed Auroral Mapper (JIRAM) targeted the northern and southern polar regions several times. The analyses of the acquired images and spectra confirmed a significant presence of methane (CH4) near both poles through its 3.3 μm emission overlapping the H3+ auroral feature at 3.31 μm. Neither acetylene (C2H2) nor ethane (C2H6) have been observed so far. The analysis method, developed for the retrieval of H3+ temperature and abundances and applied to the JIRAM-measured spectra, has enabled an estimate of the effective temperature for methane peak emission and the distribution of its spectral contribution in the polar regions. The enhanced methane inside the auroral oval regions in the two hemispheres at different longitude suggests an excitation mechanism driven by energized particle precipitation from the magnetosphere.

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.

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.

Comparison of Dawn and Dusk Precipitating Electron Energy Populations Shortly After the Initial Shock for the January 10th, 1997 Magnetic Cloud

NASA Technical Reports Server (NTRS)

Spann, J.; Germany, G.; Swift, W.; Parks, G.; Brittnacher, M.; Elsen, R.

1997-01-01

The observed precipitating electron energy between 0130 UT and 0400 UT of January 10 th, 1997, indicates that there is a more energetic precipitating electron population that appears in the auroral 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 auroral 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 auroral electrons. 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 electron population will be presented.

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.

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.;

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.;

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.

Using Wave and Energetic Particle Observation on Juno to Investigate Low Altitude Magnetospheric Process on Jupiter.

NASA Astrophysics Data System (ADS)

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

2017-12-01

The Juno spacecraft has now made several passes across the polar regions and low altitude equatorial region in the Jovian upper atmosphere. Here we report on a recent analysis of unique Landau resonant wave-particle interactions between low frequency waves and energetic particles which leads to characteristic butterfly distributions in the sub-auroral upper atmosphere of Jupiter. We also report on the characteristics of diffuse auroral precipitation observed by the JEDI and JADE energetic particle detectors equatorward of the main auroral oval, and relate this to remote sensing of the Jovian aurora by the UVS instrument on Juno. The loss cone distributions, measured by the JEDI particle detector, have also been used to investigate the spatial distribution of low altitude anomalies in the Jovian magnetic field.

OUTER RADIATION BELT AND AURORAS

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

Gorchakov, E.V.

1961-01-01

Data obtained from Sputnik IH were used to determine the high-latitude boundary of the outer radiation belt and to interpret the nature of auroras. At the heights at which the auroras were observed, the outer boundary of the belt (69 deg north geomagnetic latitude) practically coincides with the auroral zone maximum (70 deg north geomagnetic latitude), while the maximum intensity of the outer belt near the earth lies at about 55 deg north geomagnetic latitude, i.e., at latitudes 15 deg below the auroral maximum. Consequently, auroras near the zone of maximum cannot be caused by the penetration into the atmospheremore » of electrons from the outer belt with energies on the order of 0.1 Mev (the mean energy of electrons in the outer belt). Other investigators have reported the detection of lowenergy streams at 55,000 to 75,000 km from the center of the earth in the equatorial plane. Moving toward the surface of the earth along the force lines of the magnetic field, electron streams of this type will reach the earth precisely in the region of the auroral zone maximum. It is considered possible that the electron streams are trapped at these distances from the earth and are at least partially responsible for auroras in the region of maximum. The existence of two maxima in the latitudinal distribution of auroral frequency, which attests to differert mechanisms of aurora formation, favors this hypothesis. In the region of the basic auroral maximum (70 deg north geomagnetic latitude) the auroras are the result of the invasion of belt particles, while in the region of the additional maximum (about 80 deg north geomagnetic latitude) they are caused by the direct penetration of corpuscular streams into the atmosphere. (OTS)« less

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.

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.

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.

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

Juno Ultraviolet Spectrograph (Juno-UVS) Observations of Jupiter during Approach

NASA Astrophysics Data System (ADS)

Gladstone, Randy; Versteeg, Maarten; Greathouse, Thomas K.; Hue, Vincent; Davis, Michael; Gerard, Jean-Claude; Grodent, Denis; Bonfond, Bertrand

2016-10-01

We present the initial results from Juno Ultraviolet Spectrograph (Juno-UVS) observations of Jupiter obtained during approach in June 2016. Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes all important ultraviolet (UV) emissions from the H2 bands and the H Lyman series which are produced in Jupiter's auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4 x 4 cm2 input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a "dog-bone" shape 7.2° long, in three sections of 0.2°, 0.025°, and 0.2° width (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses UV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno's spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter's auroral morphology and brightness to provide context for in situ measurements by Juno's particle instruments. Prior to Jupiter Orbit Insertion (JOI) on July 5, Juno approach observations provide a rare opportunity to correlate local solar wind conditions with Jovian auroral emissions. Some of Jupiter's auroral emissions (e.g., polar emissions) may be controlled or at least affected by the solar wind. Here we compare synoptic Juno-UVS observations of Jupiter's auroral emissions (~40 minutes per hour, acquired during 2016 June 3-30) with in situ solar wind observations, as well as related Jupiter observations obtained from Earth.

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.

Characteristics of spacecraft charging in low Earth orbit

NASA Astrophysics Data System (ADS)

Anderson, Phillip C.

2012-07-01

It has been found that the DMSP spacecraft at 840 km can charge to very large negative voltages (up to -2000 V) when encountering intense precipitating electron events (auroral arcs). We present an 11-year study of over 1600 charging events, defined as when the spacecraft charged to levels exceeding 100 V negative during an auroral crossing. The occurrence frequency of events was highly correlated with the 11-year solar cycle with the largest number of events occurring during solar minimum. This was due to the requirement that the background thermal plasma density be low, at most 104 cm-3. During solar maximum, the plasma density is typically well above that level due to the solar EUV ionizing radiation, and although the occurrence frequency of auroral arcs is considerably greater than at solar minimum, the occurrence of high-level charging is minimal. As a result of this study, we produced a model spectrum for precipitating electrons that can be used as a specification for the low-altitude auroral charging environment. There are implications from this study on a number of LEO satellite programs, including the International Space Station, which does enter the auroral zone, particularly during geomagnetic activity when the auroral boundary can penetrate to very low latitudes. The plasma density in the ISS orbit is usually well above the minimum required density for charging. However, in the wake of the ISS, the plasma density can be 2 orders of magnitude or more lower than the background density and thus conditions are ripe for charging.

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.

Beyond the Electrostatic Ionosphere: Dynamic Coupling of the Magnetosphere and Ionosphere

NASA Astrophysics Data System (ADS)

Lysak, R. L.; Song, Y.

2017-12-01

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 auroral electrons, which form the Alfvénic aurora. Since these electrons are relatively low in energy (hundreds of eV to a few keV), they produce auroral emissions as well as ionization at higher altitudes. Therefore, they can produce localized columns of ionization that lead to structuring in the auroral 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 auroral arc. The acceleration of electrons and ions produces a density cavity at higher altitudes that favors the formation of parallel electric fields. Furthermore, the precipitating electrons will produce secondary and backscattered electrons 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 auroral arc formation.

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitation, Plasma Waves, and Convection Observed by Polar

NASA Technical Reports Server (NTRS)

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.;

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.

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

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.

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.

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

NASA Astrophysics Data System (ADS)

Hatch, Spencer M.; LaBelle, James; Lotko, William; Chaston, Christopher C.; Zhang, Binzheng

2017-12-01

We investigate the influence of the interplanetary magnetic field (IMF) clock angle ϕIMF on high-latitude inertial Alfvén wave (IAW) activity in the magnetosphere-ionosphere transition region using Fast Auroral SnapshoT (FAST) satellite observations. We find evidence that negative IMF Bz coincides with nightside IAW power generation and enhanced rates of IAW-associated electron energy deposition, while positive IMF Bz coincides with enhanced dayside wave and electron energy deposition. Large (≳ 5 nT) negative IMF By coincides with enhanced postnoon IAW power, while large positive IMF By coincides with enhanced but relatively weaker prenoon IAW power. For each ϕIMF orientation we compare IAW Poynting flux and IAW-associated electron energy flux distributions with previously published distributions of Alfvénic Poynting flux over ˜2-22 mHz, as well as corresponding wave-driven electron energy deposition derived from Lyon-Fedder-Mobarry global MHD simulations. We also compare IAW Poynting flux distributions with distributions of broad and diffuse electron number flux, categorized using an adaptation of the Newell et al. (2009) precipitation scheme for FAST. Under negative IMF Bz in the vicinity of the cusp (9.5-14.5 magnetic local time), regions of intense dayside IAW power correspond to enhanced diffuse electron number flux but relatively weaker broadband electron precipitation. Differences between cusp region IAW activity and broadband precipitation illustrate the need for additional information, such as fields or pitch angle measurements, to identify the physical mechanisms associated with electron precipitation in the vicinity of the cusp.

Excitation of high-frequency electromagnetic waves by energetic electrons with a loss cone distribution in a field-aligned potential drop

NASA Technical Reports Server (NTRS)

Fung, Shing F.; Vinas, Adolfo F.

1994-01-01

The electron cyclotron maser instability (CMI) driven by momentum space anisotropy (df/dp (sub perpendicular) greater than 0) has been invoked to explain many aspects, such as the modes of propagation, harmonic emissions, and the source characteristics of the auroral kilometric radiation (AKR). Recent satellite observations of AKR sources indicate that the source regions are often imbedded within the auroral acceleration region characterized by the presence of a field-aligned potential drop. In this paper we investigate the excitation of the fundamental extraordinary mode radiation due to the accelerated electrons. The momentum space distribution of these energetic electrons is modeled by a realistic upward loss cone as modified by the presence of a parallel potential drop below the observation point. On the basis of linear growth rate calculations we present the emission characteristics, such as the frequency spectrum and the emission angular distribution as functions of the plasma parameters. We will discuss the implication of our results on the generation of the AKR from the edges of the auroral density cavities.

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.

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).

Effect of double layers on magnetosphere-ionosphere coupling

NASA Technical Reports Server (NTRS)

Lysak, Robert L.; Hudson, Mary K.

1987-01-01

The Earth's auroral zone contains dynamic processes occurring on scales from the length of an auroral zone field line which characterizes Alfven wave propagation to the scale of microscopic processes which occur over a few Debye lengths. These processes interact in a time-dependent fashion since the current carried by the Alfven waves can excite microscopic turbulence which can in turn provide dissipation of the Alfven wave energy. This review will first describe the dynamic aspects of auroral current structures with emphasis on consequences for models of microscopic turbulence. A number of models of microscopic turbulence will be introduced into a large-scale model of Alfven wave propagation to determine the effect of various models on the overall structure of auroral currents. In particular, the effects of a double layer electric field which scales with the plasma temperature and Debye length is compared with the effect of anomalous resistivity due to electrostatic ion cyclotron turbulence in which the electric field scales with the magnetic field strength. It is found that the double layer model is less diffusive than in the resistive model leading to the possibility of narrow, intense current structures.

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.

Universal time dependence of nighttime F region densities at high latitudes

NASA Technical Reports Server (NTRS)

De La Beaujardiere, O.; Wickwar, V. B.; Caudal, G.; Holt, J. M.; Craven, J. D.; Frank, L. A.; Brace, L. H.

1985-01-01

Coincident auroral-zone experiments using three incoherent-scatter radars at widely spaced longitudes are reported. The observational results demonstrate that, during the night, the F layer electron density is strongly dependent on the longitude of the observing site. Ionization patches were observed in the nighttime F region from the Chatanika and EISCAT radars, while densities observed from the Millstone radar were substantially smaller. The electron density within these maxima is larger at EISCAT than at Chatanika. When observed in the midnight sector auroral zone, these densities had a peak density at a high altitude of 360-475 km. The density was maximum when EISCAT was in the midnight sector and minimum when Millstone was in the midnight sector. A minimum in insolation in the auroral zone occurs at the UT when Millstone is in the midnight sector.

Statistical study of phase relationships between magnetic and plasma thermal pressures in the near-earth magnetosphere using the THEMIS satellites

NASA Astrophysics Data System (ADS)

Nishi, K.; Kazuo, S.

2017-12-01

The auroral finger-like structures appear in the equatorward part of the auroral oval in the diffuse auroral region, and contribute to the auroral fragmentation into patches during substorm recovery phase. In our previous presentations, we reported the first conjugate observation of auroral finger-like structures using the THEMIS GBO cameras and the THEMIS satellites, which was located at a radial distance of 9 Re in the dawnside plasma sheet. In this conjugate event, we found anti-phase fluctuation of plasma pressure and magnetic pressure with a time scale of 5-20 min in the plasma sheet. This observational fact is consistent with the idea that the finger-like structures are caused by a pressure-driven instability in the balance of plasma and magnetic pressures in the magnetosphere. Then we also searched simultaneous observation events of auroral finger-like structures with the RBSP satellites which have an apogee of 5.8 Re in the inner magnetosphere. Contrary to the first result, the observed variation of plasma and magnetic pressures do not show systematic phase relationship. In order to investigate these phase relationships between plasma and magnetic pressures in the magnetosphere, we statistically analyzed these pressure data using the THEMIS-E satellite for one year in 2011. In the preliminary analysis of pressure variation spectra, we found that out of phase relationship between magnetic and plasma pressures occupied 40 % of the entire period of study. In the presentation, we will discuss these results in the context of relationships between the pressure fluctuations and the magnetospheric instabilities that can cause auroral finger-like structures.

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.

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

Auroral displays near the 'foot' of the field line of the ATS-5 satellite

NASA Technical Reports Server (NTRS)

Akasofu, S.-I.; Deforest, S.; Mcilwain, C.

1974-01-01

Summary of an extensive correlative study of ATS-5 particle and magnetic field data with all-sky photographs from Great Whale River which is near the 'foot' of the field lines passing through the ATS-5 satellite. In particular, an effort is made to identify specific particle features with specific auroral displays during substorms, such as a westward traveling surge, poleward expansive motion, and drifting patches. It is found that, in early evening hours, the first encounter of ATS-5 with hot plasma is associated with the equatorward shift of the diffuse aurora, but not necessarily with westward traveling surges (even when the satellite is embedded in the plasma sheet). In the midnight sector, an injection corresponds very well to the initial brightening of an auroral arc. Specific features of morning sector auroras are difficult to correlate with specific particle features.

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.

First Look at the 3-channel Photometer Data from RENU2

NASA Astrophysics Data System (ADS)

Hecht, J. H.; Brinkman, D. G.; Clemmons, J. H.; Walterscheid, R. L.; Evans, J. S.; Fritz, B.; Lessard, M.

2016-12-01

The Rocket Experiment for Neutral Upwelling-2 (RENU2) rocket launched north towards the cusp region from Andoya, Norway at 735 UT on December 12th 2015. It included a 3-channel forward looking photometer which included narrow-band interference filters at the following wavelengths: (1) 391.4 nm to measure the relatively bright N2+(0,0) band, primarily excited in cusp aurora via resonant scattering of solar light, (2) 557.7 nm, the auroral green line, which is seen in both dayglow emission (very weakly) and when auroral precipitation is present, and (3) 630.0 nm, the auroral redline, which is also excited in the dayglow and by low energy auroral electrons typically present in the cusp. Averaging over the 2 seconds, to minimize out the rocket spin modulation, revealed a volume emission rate profile as a function of altitude that showed dayglow and resonant scattering emission from all three features on the up leg before the cusp aurora region was entered, and a combination of this and auroral emission on the down leg. Noteworthy on the down leg was a sudden increase in the 391.4 nm emission strongly suggestive of an increase in N2+ ions above the rocket. The data are compared to results of AURIC and B3C model runs where electron data from the EPLAS instrument were used to provide the electron spectra. This comparison revealed information not only about the N2+ ion and atomic oxygen density but also showed, via the effects of the different lifetime of the red and green emissions, that there were many short timescale bursts of precipitation lasting much less than 1 second.

Observations of narrow microburst trains in the geomagnetic storm of August 4-6, 1972

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

Brown, R.R.

1973-04-01

In the intense geomagnetic disturbances of early August 1972, auroral zone microburst trains were observed at balloon altitude and found to be significantly narrower in burst width and spacing than microbursts found previously at the same site. These observations suggest that the spacing of microburst peaks, as well as their width, is related to variations in the power spectrum of a magnetospheric acceleration process rather than the bounce motions of electrons in the geomagnetic field or the modulation of electron precipitation by drift waves in magnetospheric plasma. In the geomagnetic activity that followed the solar flares in early August 1972,more » intense fluxes of auroral x rays were encountered during balloon flights launched from College, Alaska. Although much of the time variations of the x-ray fluxes observed during these flights represented known features of electron precipitation at auroral latitudes, one new and distinct feature was evident. In particular, it was found that the widths and spacings of auroral zone microbursts (Anderson and Milton, 1964) on this occasion were significantly smaller than those observed previously on many balloon flights from the same site. Thus, instead of microburst trains with widths at half-intensity points of ~0.2 sec and spacings of ~0.6 sec, the majority of the microbursts encountered on two flights from College had widths of ~0.1 sec and spacings of ~0.4 sec. (auth)« less

Superthermal electron processes in the upper atmosphere of Uranus: Aurora and electroglow

NASA Technical Reports Server (NTRS)

Waite, J. H., Jr.; Chandler, M. O.; Yelle, R. V.; Sandel, B. R.

1987-01-01

Strong ultraviolet emissions from the upper atmosphere of Uranus suggest that both auroral and electroglow phenomena are of significant aeronomical consequences in the structure of the upper atmosphere. Combined modeling and data analysis were performed to determine the effect of electroglow and auroral phenomena on the global heat and atomic hydrogen budgets in the Uranus upper atmosphere. The results indicate that the auroral and electroglow heat sources are not adequate to explain the high exospheric temperature observed at Uranus, but that the atomic hydrogen supplied by these processes is more than sufficient to explain the observations. The various superthermal electron distributions modeled have significantly different efficiencies for the various processes such as UV emission, heating, ionization, and atomic hydrogen production, and produce quite different H2 band spectra. However, additional information on the UV spectra and global parameters is needed before modeling can be used to distinguish between the possible mechanisms for electroglow.

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.

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.

VLF remote sensing of the ambient and modified lower ionosphere

NASA Astrophysics Data System (ADS)

Demirkol, Mehmet Kursad

2000-08-01

Electron density and temperature changes in the D region are sensitively manifested as changes in the amplitude and phase of subionospheric Very Low Frequency (VLF) signals propagating beneath the perturbed region. Both localized and large scale disturbances (either in electron density or temperature) in the D region cause significant scattering of VLF waves propagating in the earth- ionosphere waveguide, leading to measurable changes in the amplitude and phase of the VLF waves. Large scale auroral disturbances, associated with intensification of the auroral electrojet, as well as ionospheric disturbances produced during relativistic electron enhancements, cause characteristic changes over relatively long time scales that allow the assessment of the `ambient' ionosphere. Localized ionospheric disturbances are also produced by powerful VLF transmitting facilities such as the High Power Auroral Stimulation (HIPAS) facility, the High frequency Active Auroral Research Program (HAARP), and also by lightning discharges. Amplitude and phase changes of VLF waveguide signals scattered from such artificially heated ionospheric patches are known to be detectable. In this study, we describe a new inversion algorithm to determine altitude profiles of electron density and collision frequency within such a localized disturbance by using the measured amplitude and phase of three different VLF signals at three separate receiving sites. For this purpose a new optimization algorithm is developed which is primarily based on the recursive usage of the three dimensional version of the Long Wave Propagation, Capability (LWPC) code used to model the subionospheric propagation and scattering of VLF signals in the earth- ionosphere waveguide in the presence of ionospheric disturbances.

An investigation of ionospheric disturbances over the north-eastern region of Russia in October 2003 using auroral images and data from a network of ground-based instruments

NASA Astrophysics Data System (ADS)

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.

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 auroral images during geomagnetic disturbances as a consequence of high flaring activity of the Sun from October 19 to 29, 2003. The position of the auroral 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 electron 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 auroral 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 auroral images and data from ground-based radiophysical facilities made it possible to study the dynamics of the boundaries of the auroral oval and ionospheric trough during strong geomagnetic disturbances. A dramatic displacement of the auroral 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 electron density during the nighttime were accompanied by a substantial rise of electron (by ˜ 1500K) and ion (by ˜ 1000K) temperatures. Studying the characteristic features of the ionospheric response over the north-eastern region of Russia to strong geomagnetic disturbances is of significant interest for understanding the magnetosphere-ionosphere coupling on a global scale.

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.

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).

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.

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 implications. One specific example of interest is identifying and following the temporal and spatial evolution of regions of potential ion outflow over large spatial and temporal scales using ground-based optical observations.

Generalized Jeans' Escape of Pick-Up Ions in Quasi-Linear Relaxation

NASA Technical Reports Server (NTRS)

Moore, T. E.; Khazanov, G. V.

2011-01-01

Jeans escape is a well-validated formulation of upper atmospheric escape that we have generalized to estimate plasma escape from ionospheres. It involves the computation of the parts of particle velocity space that are unbound by the gravitational potential at the exobase, followed by a calculation of the flux carried by such unbound particles as they escape from the potential well. To generalize this approach for ions, we superposed an electrostatic ambipolar potential and a centrifugal potential, for motions across and along a divergent magnetic field. We then considered how the presence of superthermal electrons, produced by precipitating auroral primary electrons, controls the ambipolar potential. We also showed that the centrifugal potential plays a small role in controlling the mass escape flux from the terrestrial ionosphere. We then applied the transverse ion velocity distribution produced when ions, picked up by supersonic (i.e., auroral) ionospheric convection, relax via quasi-linear diffusion, as estimated for cometary comas [1]. The results provide a theoretical basis for observed ion escape response to electromagnetic and kinetic energy sources. They also suggest that super-sonic but sub-Alfvenic flow, with ion pick-up, is a unique and important regime of ion-neutral coupling, in which plasma wave-particle interactions are driven by ion-neutral collisions at densities for which the collision frequency falls near or below the gyro-frequency. As another possible illustration of this process, the heliopause ribbon discovered by the IBEX mission involves interactions between the solar wind ions and the interstellar neutral gas, in a regime that may be analogous [2].

The Role of Superthermal Electrons in the Formation of Double Layers and their Application in Space Plasmas

NASA Astrophysics Data System (ADS)

Singh, N.

2014-12-01

It is now widely recognized that superthermal electrons commonly exist with the thermal population in most space plasmas. When plasmas consisting of such electron population expand, double layers (DLs) naturally forma due to charge separation; the more mobile superthermal electrons march ahead of the thermal population, leaving a positive charge behind and generating electric fields. Under certain conditions such fields evolve into thin double layers or shocks. The double layers accelerate ions. Such double-layer formation was first invoked to explain expansion of laser produced plasmas. Since then it has been studied in laboratory experiments, and applied to (i) polar wind acceleration,(ii) the existence of low-altitude double layers in the auroral acceleration, (iii) a possible mechanism for the origination of the solar wind, (iv) the helicon double layer thrusters, and (v) the deceleration of electrons after their acceleration in solar flare events. The role of superthermal-electron driven double layers, also known as the low-altitude auroral double layers in the upward current region, in the upward acceleration of ionospheric ions is well-known. In the auroral application the upward moving superthermal electrons consist of backscattered downgoing primary energetic electrons as well as the secondary electrons. Similarly we suggest that such double layers might play roles in the acceleration of ions in the solar wind across the coronal transition region, where the superthermal electrons are supplied by magnetic reconnection events. We will present a unified theoretical view of the superthermal electron-driven double layers and their applications. We will summarize theoretical, experimental, simulation and observational results highlighting the common threads running through the various existing studies.

Ground Based Remote Sensing of Upper Atmosphere Dynamics, Thermodynamics and Composition in Support of TIMED Satellites Scientific Mission

NASA Technical Reports Server (NTRS)

2004-01-01

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 auroral line as well as band emissions. 2. Our Polar observations of auroral 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 auroral events triggered by the precipitation of auroral electrons with average energy of about 10 keV. 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).

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.

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.

Dissociative excitation of the N(+)(5S) state by electron impact on N2 - Excitation function and quenching

NASA Technical Reports Server (NTRS)

Erdman, P. W.; Zipf, E. C.

1986-01-01

Metastable N(+)(5S) ions were produced in the laboratory by dissociative excitation of N2 with energetic electrons. The resulting radiative decay of the N(+)(5S) state was observed with sufficient resolution to completely resolve the doublet from the nearby N2 molecular radiation. The excitation function was measured from threshold to 500 eV. The cross section peaks at a high electron energy and also exhibits a high threshold energy both of which are typical of dissociative excitation-ionization processes. This finding complicates the explanation of electron impact on N2 as the mechanism for the source of the 2145 A 'auroral mystery feature' by further increasing the required peak cross section. It is suggested that the apparent N(+)(5S) quenching in auroras may be an artifact due to the softening of the electron energy spectrum in the auroral E region.

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.

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.

The International Reference Ionosphere - Status 2013

NASA Astrophysics Data System (ADS)

Bilitza, Dieter

2015-04-01

This paper describes the latest version of the International Reference Ionosphere (IRI) model. IRI-2012 includes new models for the electron density and ion densities in the region below the F-peak, a storm-time model for the auroral E-region, an improved electron temperature model that includes variations with solar activity, and for the first time a description of auroral boundaries. In addition, the thermosphere model required for baseline neutral densities and temperatures was upgraded from MSIS-86 to the newer NRLMSIS-00 model and Corrected Geomagnetic coordinates (CGM) were included in IRI as an additional coordinate system for a better representation of auroral and polar latitudes. Ongoing IRI activities towards the inclusion of an improved model for the F2 peak height hmF2 are discussed as are efforts to develop a "Real-Time IRI". The paper is based on an IRI status report presented at the 2013 IRI Workshop in Olsztyn, Poland. The IRI homepage is at

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.

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.

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.

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.

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.

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).

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.

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.

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.

Global modeling of thermospheric airglow in the far ultraviolet

NASA Astrophysics Data System (ADS)

Solomon, Stanley C.

2017-07-01

The Global Airglow (GLOW) model has been updated and extended to calculate thermospheric emissions in the far ultraviolet, including sources from daytime photoelectron-driven processes, nighttime recombination radiation, and auroral excitation. It can be run using inputs from empirical models of the neutral atmosphere and ionosphere or from numerical general circulation models of the coupled ionosphere-thermosphere system. It uses a solar flux module, photoelectron generation routine, and the Nagy-Banks two-stream electron transport algorithm to simultaneously handle energetic electron distributions from photon and auroral electron sources. It contains an ion-neutral chemistry module that calculates excited and ionized species densities and the resulting airglow volume emission rates. This paper describes the inputs, algorithms, and code structure of the model and demonstrates example outputs for daytime and auroral cases. Simulations of far ultraviolet emissions by the atomic oxygen doublet at 135.6 nm and the molecular nitrogen Lyman-Birge-Hopfield bands, as viewed from geostationary orbit, are shown, and model calculations are compared to limb-scan observations by the Global Ultraviolet Imager on the TIMED satellite. The GLOW model code is provided to the community through an open-source academic research license.

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 to drive the cyclotron maser instability. The high velocity of the Juno spacecraft near perijove ( 50 km/s) allows observations for of very low energy ions in the spacecraft ram direction, down to below 1 eV/q for protons.

Computer simulation of the Farley-Buneman instability and anomalous electron heating in the auroral ionosphere

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

Machida, S.; Goertz, C.K.

1988-09-01

We study the nonlinear saturation of the Farley-Buneman instability in a collisional plasma by a 2 1/2 dimensional electrostatic particle simulation which includes inelastic and elastic collisions of electrons and elastic collision of ions with neutrals. In our simulation, a uniform convection electric field is applied externally so that the relative velocity between the electrons and ions is greater than the ion sound speed and destabilizes the instability. We find a nonlinear frequency shift from higher to lower frequencies and diffusion of the wave spectrum in two dimensional wave number space. We are especially interested in finding whether the saturatedmore » wave turbulence can account for the anomalous heating rates observed in the polar ionosphere by Schlegel and St.-Maurice (1981). We find that the dominant mechanism for electron heating is due to an enhanced effective electron collision frequency and hence enhanced resistive heating as suggested by Primdahl (1986) and Robinson (1986) and not due to the heating of electrons by the electric field of the waves parallel to the magnetic field. For the ionospheric conditions discussed by Schlegel and St.-Maurice (1981) we find an anomalous heating rate of about 4 x 10/sup -7/ W/m/sup 3/. copyright American Geophysical Union 1988« less

Effect of double layers on magnetosphere-ionosphere coupling

NASA Technical Reports Server (NTRS)

Lysak, Robert L.; Hudson, Mary K.

1987-01-01

The dynamic aspects of auroral current structures are reviewed with emphasis on consequences for models of microscopic turbulence (MT). A number of models of MT are introduced into a large-scale model of Alfven wave propagation to determine the effect of various models on the overall structure of auroral currents. The effect of a double layer (DL) electric field which scales with the plasma temperature and the Debye length is compared with the effect of anomalous resistivity due to electrostatic ion cyclotron turbulence in which the electric field scales with the magnetic field strength. It is shown that the DL model is less diffusive than the resistive model, indicating the possibility of narrow intense current structures.

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.

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.

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, this data set enables the quiet-background ionosphere to be established as a function of season and local time. This quiet-background ionosphere has the unique attribute that it has self-consistent altitude profiles of the density and the temper-ature. This we believe is a true fiduciary reference for the IRI in a high latitude region, that is otherwise particularly difficult to quantify.

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.

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.

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.;

Electron impact vibrational excitation of carbon monoxide in the upper atmospheres of Mars and Venus

NASA Astrophysics Data System (ADS)

Campbell, L.; Allan, M.; Brunger, M. J.

2011-09-01

Infrared emission from CO in the upper atmospheres of Mars, Venus and several other planets is a subject of current theoretical and experimental interest. Electron impact excitation makes a contribution that has not been included in previous studies. Given this, and recent new measurements of absolute cross sections for low-energy electron impact excitation of the vibrational levels of the ground state of CO, results from calculations are presented showing the contribution of electron impact relative to emissions by other mechanisms. It is demonstrated that emissions due to the impact of thermal, photo- and auroral electrons are generally small compared to sunlight-driven (fluorescence and photolysis) emissions, but with some exceptions. It is also shown that thermal-electron emissions may dominate over other processes at nighttime at Mars and that auroral emissions certainly do so. While measurements and other calculations do not appear to be available for Venus, the volume emission rates presented should be valuable in planning such measurements.

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.

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.

The Mars diffuse aurora: A model of ultraviolet and visible emissions

NASA Astrophysics Data System (ADS)

Gérard, J.-C.; Soret, L.; Shematovich, V. I.; Bisikalo, D. V.; Bougher, S. W.

2017-05-01

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar activity on several occasions from the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and violet auroral emissions for initial electron energies extending from 0.25 to 200 keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6 nm and the Fox-Duffendack-Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2 nm and CI 156.1 nm and 165.7 nm multiplets. We calculate the nadir and limb production rates of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 50-200 keV produce maximum CO2+ UVD emission below 75 km, in agreement with the MAVEN observations. We calculate the efficiency of photon production per unit precipitated electron power. The strongest emissions are the CO2+ FDB, UVD and CO Cameron bands and the oxygen emission at 297.2 nm. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below about 110 km. As a consequence, we show that the Cameron band emission is expected to peak at a higher altitude than the CO2+ UVD and FDB bands. Collisional quenching also causes the intensity ratio of the CO2+ UVD to CO Cameron bands to increase below ∼100 km in the energetic diffuse aurora.

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.

Anomalous electron heating effects on the E region ionosphere in TIEGCM

NASA Astrophysics Data System (ADS)

Liu, Jing; Wang, Wenbin; Oppenheim, Meers; Dimant, Yakov; Wiltberger, Michael; Merkin, Slava

2016-03-01

We have recently implemented a new module that includes both the anomalous electron heating and the electron-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 auroral precipitation heating in the TIEGCM. The induced changes in E region electron temperature in the auroral 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.

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.

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.

On the location of Steve, the mysterious subauroral feature

NASA Astrophysics Data System (ADS)

Gallardo-Lacourt, B.; Nishimura, Y.; Donovan, E.; Gillies, D. M.; Spanswick, E.; Archer, W. E.; MacDonald, E.; Knudsen, D. J.

2017-12-01

Over the past year, there has been an exciting development in auroral research with the finding of a new subauroral phenomenon called Steve. Although Steve has been documented by amateur night sky watchers for decades, this is a new phenomenon about which scientists know very little. From optical observations including images from amateur photographers, Steve is a luminous arc that is narrow in north-south extent, and thousands of kilometers in east-west extent. We use auroral images from the ground-based THEMIS all-sky imagers and the Redline Geospace Observatory (REGO) array to identify Steve events. In addition, we use data from Meridian Scanning Photometers (NORSTAR and FESO) that measure brightness of H-β proton auroral emission at 4861Å. We surveyed data from December 2007 up to May 2017. Our observations suggest that Steve is always located equatorward of the proton aurora, and thus is not a traditional electron auroral arc, a feature which is always poleward of the peak in proton auroral brightness. Further, we have developed a picture of the magnetospheric region which is magnetically conjugate to Steve, and the magnetospheric conditions which give rise to the feature.

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.

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.

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->

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.

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.

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 precipitation due to the combination of these two mechanisms coincides spatially with observed auroral brightening during the disturbed event.

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.

Excitation of Plasma Waves in Aurora by Electron Beams

NASA Technical Reports Server (NTRS)

daSilva, C. E.; Vinas, A. F.; deAssis, A. S.; deAzevedo, C. A.

1996-01-01

In this paper, we study numerically the excitation of plasma waves by electron beams, in the auroral 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 electron 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 electrons and ions species (H(+) and O(+)) temperature, density or the electron 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 auroral acceleration processes, by wave-particle interaction.

Particle and Fields Observations Associated with Discrete Aurora at Mars: A Dual Spacecraft Perspective Using MAVEN and MEX

NASA Astrophysics Data System (ADS)

Soobiah, Y. I. J.; Espley, J. R.; Connerney, J. E. P.; Gruesbeck, J.; DiBraccio, G. A.; Schneider, N. M.; Jain, S.; Mitchell, D. L.; Mazelle, C. X.; Halekas, J. S.; Andersson, L.; Brain, D.; Lillis, R. J.; McFadden, J. P.; Deighan, J.; McClintock, B.; Jakosky, B. M.; Frahm, R.; Winningham, D.; Coates, A. J.; Holmstrom, M.

2017-12-01

NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft has observed a variety of distinct auroral types at Mars and related processes relevant to the escape of the Martian atmosphere. MAVEN's Imaging Ultraviolet Spectrograph (IUVS) instrument has measured 1) diffuse aurora over widespread regions of Mars' northern hemisphere, 2) discrete aurora spatially confined to localized patches around regions of strong crustal magnetic field and 3) proton aurora from limb brightening of Lyman-α emission. The processes involved in the occurrence of discrete aurora at Mars are not yet well understood. This study presents MAVEN IUVS and Particle and Fields Package (PFP) observations of contemporaneous particle and field signatures and discrete aurora at Mars. Discrete aurora observed in limb scans occur in association with patches of electrons in the optical shadow of Mars. The electron signatures display a range of field aligned (toward Mars) electron energy spectra, from electrons that are not accelerated (sometimes including photoelectron peaks) to accelerated electrons. These are observed in association with a range of magnetic field orientations, from horizontal to radial magnetic field directions. Observations obtained at low altitude over the nightside by MAVEN and the more distant Mars Express' (MEX) Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) are compared to investigate transport of electrons from plasma sheet and `inverted-V' electron signatures from the magnetotail to low altitudes.

Energetic Electron Transport in the Inner Magnetosphere During Geomagnetic Storms and Substorms

NASA Technical Reports Server (NTRS)

McKenzie, D. L.; Anderson, P. C.

2005-01-01

We propose to examine the relationship of geomagnetic storms and substorms and the transport of energetic particles in the inner magnetosphere using measurements of the auroral X-ray emissions by PIXIE. PIXIE provides a global view of the auroral oval for the extended periods of time required to study stormtime phenomena. Its unique energy response and global view allow separation of stormtime particle transport driven by strong magnetospheric electric fields from substorm particle transport driven by magnetic-field dipolarization and subsequent particle injection. The relative importance of substorms in releasing stored magnetospheric energy during storms and injecting particles into the inner magnetosphere and the ring current is currently hotly debated. The distribution of particles in the inner magnetosphere is often inferred from measurements of the precipitating auroral particles. Thus, the global distributions of the characteristics of energetic precipitating particles during storms and substorms are extremely important inputs to any description or model of the geospace environment and the Sun-Earth connection. We propose to use PIXIE observations and modeling of the transport of energetic electrons to examine the relationship between storms and substorms.

What is the Relationship Between Heavy Ion Outflow and High-Latitude Energetic Particle Precipitation?

NASA Technical Reports Server (NTRS)

Wilson, Gordon R.

2001-01-01

This document is the fourth quarter progress report for year two on contract NAW-99002 'What is the relationship between heavy ion outflow and high latitude energetic particle precipitation'. In this project we are studying the relationship between the fluxes, mean energies, and field-aligned flow speeds of escaping suprathermal H+ and O+ measured by the TEAMS instrument on FAST and the energy flux of precipitating electrons obtained form the LBHL images taken by the Ultraviolet Imagery (UVI) camera on the Polar spacecraft. We have analyzed data from three time intervals, 7-11 Feb, 25-31 Jan, and 1-6 Feb 1997. We find that there indeed is a relationship between the O+ escape fluxes and the intensity of the aurora at the foot point of the field line. The time delay between an auroral intensification and the corresponding increase in escape flux is very short, only a few minutes. At low auroral luminosity the relationship between escape flux and luminosity appears to break down due possibly to the lack of sensitivity of the auroral emissions to large fluxes of low energy electrons.

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

Ishimoto, M.; Meng, C.; Romick, G.J.

The UV spectra over the southern hemisphere nightside auroral oval have been obtained from an AFGL spectral/photometric experiment on board the low-altitude polar-orbiting S3-4 satellite. A detailed analysis of nightside auroral spectra from seven orbits between mid-May and June 1978 was performed to estimate the average energy and total energy flux of incident electrons. This study was based on observations of the N{sub 2} LBH (3-10) (1928-A) band and the N{sub 2} VK (0-5) (2604 A) band emission intensities and the application of model calculations. Comparison of the estimated quantities with the statistical satellite measurement of incident particles indicates thatmore » the LBH (3-10) band emission intensity can be used to estimate the total energy flux of incident electrons, similar to the N{sub 2}(+) 1N (0-0) (3914 A) band emission intensity in the visible region. In addition, the ratio of the LBH (3-10) to the VK (0-5) bande mission intensities indicates the average energy of incident auroral electrons in much the same way that the N{sub 2}(+)1N (0-0) and O I (6300 A) emission ratio does in the visible region. This study shows the use of different constituent emissions, model calculations, and synthetic spectra to infer the inherent possibilities in these types of studies.« less

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

Ishimoto, M.; Meng, C.; Romick, G.J.

The UV spectra over the southern hemisphere nightside auroral oval have been obtained from an AFGL spectral/photometric experiment on board the low-altitude polar-orbiting S3--4 satellite. A detailed analysis of nightside auroral spectra from seven orbits between mid-May and June 1978 was performed to estimate the average energy and total energy flux of incident electrons. This study was based on observations of the N/sub 2/ LBH (3--10) (1928 A) band and the N/sub 2/ VK (0--5) (2604 A) band emission intensities and the application of model calculations by Strickland et al. (1983) and Daniell and Strickland (1986). Comparison of the estimatedmore » quantities with the statistical satellite measurement of incident particles by Hardy et al. (1985) indicates that the LBH (3--10) band emission intensity can be used to estimate the total energy flux of incident electrons, similar to the N/sub 2//sup +/ 1N (0--0) (3914 A) band emission intensity in the visible region. In addition, the ratio of the BLH (3--10) to the VK (0--5) band emission intensities indicates the average energy of incident auroral electrons in much the same way that the N/sub 2//sup +/ IN (0--0) and O I (6300 A) emission ratio does in the visible region.« less

ELF waves and ion resonances produced by an electron beam emitting rocket in the ionosphere

NASA Technical Reports Server (NTRS)

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

1986-01-01

Results are reported from the ECHO-6 electron-beam-injection experiment, performed in the auroral-zone ionosphere on March 30, 1983 using a sounding rocket equipped with two electron guns and a free-flying plasma-diagnostics instrument package. The data are presented in extensive graphs and diagrams and characterized in detail. Large ELF wave variations, superposed on the strong beam-sector-directed quasi-dc component, are observed in the 100-eV beam-induced plasma when the beam is injected in a transverse spiral, but not when it is injected upward parallel to the magnetic-field line. ELF activity is found to be suppressed whenever the rocket passed through field lines with auroral activity, suggesting that the waves are produced by the interaction of the beam potentials, plasma currents, and return currents neutralizing the accelerator payload.

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.

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.

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.

Occurrence and average behavior of pulsating aurora

NASA Astrophysics Data System (ADS)

Partamies, N.; Whiter, D.; Kadokura, A.; Kauristie, K.; Nesse Tyssøy, H.; Massetti, S.; Stauning, P.; Raita, T.

2017-05-01

Motivated by recent event studies and modeling efforts on pulsating aurora, which conclude that the precipitation energy during these events is high enough to cause significant chemical changes in the mesosphere, this study looks for the bulk behavior of auroral pulsations. Based on about 400 pulsating aurora events, we outline the typical duration, geomagnetic conditions, and change in the peak emission height for the events. We show that the auroral peak emission height for both green and blue emission decreases by about 8 km at the start of the pulsating aurora interval. This brings the hardest 10% of the electrons down to about 90 km altitude. The median duration of pulsating aurora is about 1.4 h. This value is a conservative estimate since in many cases the end of event is limited by the end of auroral imaging for the night or the aurora drifting out of the camera field of view. The longest durations of auroral pulsations are observed during events which start within the substorm recovery phases. As a result, the geomagnetic indices are not able to describe pulsating aurora. Simultaneous Antarctic auroral images were found for 10 pulsating aurora events. In eight cases auroral pulsations were seen in the southern hemispheric data as well, suggesting an equatorial precipitation source and a frequent interhemispheric occurrence. The long lifetimes of pulsating aurora, their interhemispheric occurrence, and the relatively high-precipitation energies make this type of aurora an effective energy deposition process which is easy to identify from the ground-based image data.

Preliminary Observations of Ionospheric Response to an Auroral Driver from the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) Sounding Rocket Campaign

NASA Astrophysics Data System (ADS)

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.

2012-12-01

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 auroral 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 auroral drivers inferred from inverting camera data. We compare the measured precipitating electron 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 auroral arc, the in situ electron instrument shows dispersions indicative of Alfvénic activity. We then introduce measurements of the thermal ion distribution, to examine how the auroral 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 electron 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. Further analysis of the particle data will yield the ion temperature, whose validity we will quantify by comparison to sheath models.

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 critical role in controlling nightside, upwelling O+. This thesis provides a new database, and insights into the study of oxygen ion outflows during quiet times. These results and tools will be essential for researchers working on topics involving magnetosphere-ionosphere interactions.

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.

Substorm and magnetosphere characteristic scales inferred from the SuperMAG auroral electrojet indices

NASA Astrophysics Data System (ADS)

Newell, P. T.; Gjerloev, J. W.

2011-12-01

A generalization of the traditional 12-station auroral electrojet (AE) index to include more than 100 magnetometer stations, SME, is an excellent predictor of global auroral 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 auroral precipitation is diffuse aurora; thus, these values are properties of the magnetotail thermal electron 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 distribution (with a 40% weighting) corresponds to the characteristic quiet peak, while the higher value distribution (60% weighting) is an average over the characteristic substorm peak and the subsequent prolonged recovery.

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.

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.

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

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 Climate, Volume 3, 12, 2013.

Dynamics of Auroras Conjugate to the Dayside Reconnection Region.

NASA Astrophysics Data System (ADS)

Mende, S. B.; Frey, H. U.; Doolittle, J. H.

2006-12-01

During periods of northward IMF Bz, observations of the IMAGE satellite FUV instrument demonstrated the existence of an auroral footprint of the dayside lobe reconnection region. Under these conditions the dayside "reconnection spot" is a distinct feature being separated from the dayside auroral oval. In the IMAGE data, ~100 km spatial and 2 minutes temporal resolution, this feature appeared as a modest size, 200 to 500 km in diameter, diffuse spot which was present steadily while the IMF conditions lasted and the solar wind particle pressure was large enough to create a detectable signature. Based on this evidence, dayside reconnection observed with this resolution appears to be a steady state process. There have been several attempts to identify and study the "reconnection foot print aurora" with higher resolution from the ground. South Pole Station and the network of the US Automatic Geophysical Observatories (AGO-s) in Antarctica have all sky imagers that monitor the latitude region of interest (70 to 85 degrees geomagnetic) near midday during the Antarctic winter. In this paper we present sequences of auroral images that were taken during different conditions of Bz and therefore they are high spatial resolution detailed views of the auroras associated with reconnection. During negative Bz, auroras appear to be dynamic with poleward moving auroral forms that are clearly observed by ground based imagers with a ~few km spatial resolution. During positive Bz however the extremely high latitude aurora is much more stable and shows no preferential meridional motions. It should be noted that winter solstice conditions, needed for ground based observations, produce a dipole tilt in which reconnection is not expected to be symmetric and the auroral signatures might favor the opposite hemisphere.

Use of Spectralon as a diffuse reflectance standard for in-flight calibration of earth-orbiting sensors

NASA Technical Reports Server (NTRS)

Bruegge, Carol J.; Stiegman, Albert E.; Rainen, Richard A.; Springsteen, Arthur W.

1993-01-01

Spectralon, a commercially available diffuse reflectance material made from polytetrafluoroethylene (PTFE), is being evaluated for the multiangle imaging spectroradiometer (MISR), currently under development for the Earth Observing System. Results of a series of environmental exposure tests indicate that no degradation of the optical properties was apparent following proton bombardment, and stability through UV illumination was satisfactory, provided simple cleaning and handling procedures were implemented. A buildup of several thousand volts of static charge was found to develop while simulating a rare pass through an auroral storm.

Spatial and Temporal Energy Characterization of Precipitating Electrons for the January 10th, 1997 Magnetic Cloud Event

NASA Technical Reports Server (NTRS)

Spann, J. F., Jr.; Germany, G. A.; Brittnacher, M. J.; Parks, G. K.; Elsen, R.

1997-01-01

The January 10-11, 1997 magnetic cloud event provided a rare opportunity to study auroral energy deposition under varying but intense IMF conditions. The Wind spacecraft located about 100 RE upstream monitored the IMF and plasma parameters during the passing of the cloud. The Polar Ultraviolet Imager (UVI) observed the aurora[ precipitation during the first encounter of the cloud with Earth's magnetosphere and during several subsequent substorm events. The UVI has the unique capability of measuring the energy flux and characteristic energy of the precipitating electrons through the use of narrow band filters that distinguish short and long wavelength molecular nitrogen emissions. The spatial and temporal characteristics of the precipitating electron energy will be discussed beginning with the inception of the event at the Earth early January 1 Oth and continuing through the subsidence of auroral activity on January 11th.

Rocket observations at the northern edge of the eastward electrojet

NASA Technical Reports Server (NTRS)

Cahill, L. J., Jr.; Arnoldy, R. L.; Taylor, W. W. L.

1980-01-01

The paper discusses a Nike-Tomahawk rocket launched north over quiet, late evening auroral arcs in March 1975. A northward magnetic disturbance was observed on the ground under the rocket trajectory; south of the arcs the northward electric field was 60 mV/m, indicating strong westward plasma flow. An eastward electrojet current layer was penetrated in the upward flight, and precipitating electrons were observed over each arc. Using the observed electron flux and a model of the ionosphere, the Hall and Pedersen conductivities were calculated which were used to compute the eastward and northward components of the horizontal ionospheric currents. The joule power decreased abruptly in the auroral arcs, as the precipitating electron power increased; the total dissipated power was the same inside the arcs, between them and southward. North of the aurora the electric field and dissipated power remained low; field-aligned currents carried by the observed electrons were about a factor of 3 lower than those inferred from the magnetic field measurements.

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.

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

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(3), 295-353 (2000) [2] A.Bhardwaj, and S. A. Haider, Adv. Space Res., 29(5), 745-750 (2002) [3] A. Bhardwaj and S. Raghuram, ApJ, 748:13 (2012) [4] S. H. Pandya et al.,Int. J. Mass Spectrom. 323-324, 28-33 (2012)

International reference ionosphere 1990

NASA Technical Reports Server (NTRS)

Bilitza, Dieter; Rawer, K.; Bossy, L.; Kutiev, I.; Oyama, K.-I.; Leitinger, R.; Kazimirovsky, E.

1990-01-01

The International Reference Ionosphere 1990 (IRI-90) is described. IRI described monthly averages of the electron density, electron temperature, ion temperature, and ion composition in the altitude range from 50 to 1000 km for magnetically quiet conditions in the non-auroral ionosphere. The most important improvements and new developments are summarized.

The Dartmouth Elephant plasma facility

NASA Astrophysics Data System (ADS)

Lynch, K. A.

2017-12-01

The Elephant facility in the Dartmouth Dept of Physics and Astronomyis a 1m by 2m chamber with a microwave-resonant plasma source togetherwith a higher energy electron/ion electrostatic gun. In this chamber weaim to re-create features of the auroral ionosphere including both thethermal plasma background, and the precipitating energetic auroral beam.We can manipulate the position and attitude of various sensors withinthe chamber and monitor their response to the various sources. Recentefforts have focussed on the sheath environment near and around thermalion RPA sensors and the small payloads which carry them into theionosphere.

Observation of large-scale density cavities and parametric-decay instabilities in the high-altitude discrete auroral ionosphere under pulsed electromagnetic radiation.

PubMed

Wong, A Y; Chen, J; Lee, L C; Liu, L Y

2009-03-13

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 auroral plasmas to high altitudes. Recorded positive plasma potential from satellite probes is consistent with the expulsion of electrons in the creation of density cavities. High-frequency decay spectra support the concept of parametric instabilities fed by free energy sources.

Energetic Charged Particle Component or the NO(y) Budget of the Polar Middle Atmosphere

NASA Technical Reports Server (NTRS)

Vitt, F. M.; Jackman, C. H.

1999-01-01

Analysis of nitrates measured in polar ice cap snow at a high resolution shows large variations in the nitrates. It has been shown that the nitrate signal may contain a signature of solar activity [Zeller and Dreschhoff, 19951. Reactive odd nitrogen production associated with solar particle events (SPEs) and auroral activity may be a source of some of the nitrate anomalies observed in the polar ice caps. Periods of large SPEs can lead to a production of polar atmospheric odd nitrogen in excess of the ambient sources in the polar stratosphere and mesosphere, and may leave a large nitrate signal stratified in the polar ice cap. Auroral electrons and photoelectrons produce odd nitrogen in the thermosphere, some of which may be transported to the polar (>50 degrees) mesosphere and stratosphere. Sources of odd nitrogen in the polar middle atmosphere associated with SPEs, galactic cosmic rays, and auroral electron precipitation have been quantified. The relative contributions by the energetic particles sources to the Noy budget of the polar middle atmosphere (from tropopause to 50 km, from 50 degrees to 90 degrees latitude) are compared with the nitrates observed in the polar ice sheets.

Polar Cap Disturbances: Mesosphere and Thermosphere-Ionosphere Response to Solar-Terrestrial Interactions

NASA Technical Reports Server (NTRS)

Sivjee, G.; McEwen, D.; Walterscheid, R.

2003-01-01

The Polar Cap is the Upper-Atmosphere cum Mag-netosphere region which is enclosed by the poleward boundary of the Auroral Oval and is threaded by open geomagnetic tield lines. In this region, there is normally a steady precipition (Polar "drizzle") of low energy (w 300eV) electrons that excite optical emissions from the ionosphere. At times, enhanced ionization patches are formed near the Dayside Cusp regions that drift across the Polar Cap towards the Night Sector of the Auroral Oval. Discrete auroral arcs and auroras formed during Solar Magnetic Cloud (SMC)/Coronal Mass Ejection (CME) events are also observed in the Polar Cap. Spectrophotometric observations of all these Polar Cap phenomena provide a measure of the average energy as well a energy flux of the electrons precipitating in the Polar Cap region during these disturbances. Such measurements also point to modulations of the Polar Cap Mesosphere-Lower Thermosphere (MLT) air density and temperature by zonally symmetric tides whose Hough functions peak in the Polar region. MLT cooling during Stratospheric Warming events and their relation to Polar Vortex and associated Gravity wave activities are also observed at the Polar Cap sites.

Latitude Dependence of Low-Altitude O+ Ion Upflow: Statistical Results From FAST Observations

NASA Astrophysics Data System (ADS)

Zhao, K.; Chen, K. W.; Jiang, Y.; Chen, W. J.; Huang, L. F.; Fu, S.

2017-09-01

We introduce a statistical model to explain the latitudinal dependence of the occurrence rate and energy flux of the ionospheric escaping ions, taking advantage of advances in the spatial coverage and accuracy of FAST observations. We use a weighted piecewise Gaussian function to fit the dependence, because two probability peaks are located in the dayside polar cusp source region and the nightside auroral oval zone source region. The statistical results show that (1) the Gaussian Mixture Model suitably describes the dayside polar cusp upflows, and the dayside and the nightside auroral oval zone upflows. (2) The magnetic latitudes of the ionospheric upflow source regions expand toward the magnetic equator as Kp increases, from 81° magnetic latitude (MLAT) (cusp upflows) and 63° MLAT (auroral oval upflows) during quiet times to 76° MLAT and 61° MLAT, respectively. (3) The dayside polar cusp region provides only 3-5% O+ upflows among all the source regions, which include the dayside auroral oval zone, dayside polar cusp, nightside auroral oval zone, and even the polar cap. However, observations show that more than 70% of upflows occur in the auroral oval zone and that the occurrence probability increases at the altitudes of 3500-4200 km, which is considered to be the lower altitude boundary of ion beams. This observed result suggests that soft electron precipitation and transverse wave heating are the most efficient ion energization/acceleration mechanisms at the altitudes of FAST orbit, and that the parallel acceleration caused by field-aligned potential drops becomes effective above that altitude.

Roles of Magnetic Reconnection and Developments of Modern Theory^*

NASA Astrophysics Data System (ADS)

Coppi, B.

2007-11-01

The role of reconnection was recognized in Solar and Space Physics and auroral substorms were suggested to originate in the night-side of the Earth's magnetosphere as a result collisionless reconnectionootnotetextB. Coppi, Nature 205, 998 (1965). well before the kind of modern theory employed for this became applied to laboratory plasmas. Experiments have reached low collisionality regimes where, like in space plasmas, the features of the electron distribution and in particular of the electron temperature gradient become important and the factors contributing to the electron thermal energy balance equation (transverse thermal and longitudinal diffusivities, or electron Landau dampingootnotetextB. Coppi, J.W.-K. Mark, L. Sugiyama, G. Bertin, Phys. Rev. Letters 42, 1058 (1978) and J. Drake, et al., Phys. Fluids 26, 2509 (1983). play a key role. For this an asymptotic theory of modes producing macroscopic islands has been developed involving 3 regions, the innermost one related to finite resistivity and the intermediate one to the finite ratio of the to thermal conductivitiesootnotetextB. Coppi, C. Crabtree, and V. Roytershteyn contribution to Paper TH/R2-19, I.A.E.A. Conference 2006.,^4. A background of excited micro-reconnecting modes, driven by the electron temperature gradient, is considered to make this ratio significantootnotetextB. Coppi, in``Collective Phenomena in Macroscopic Systems'' Eds. G. Bertin et al. (World Scientific, 2007) MIT-LNS Report 06/11(2006). ^*Supported in part by the US D.O.E.

Effect of an MLT dependent electron loss rate on the magnetosphere-ionosphere coupling

NASA Astrophysics Data System (ADS)

Gkioulidou, Matina; Wang, Chih-Ping; Wing, Simon; Lyons, Larry R.; Wolf, Richard A.; Hsu, Tung-Shin

2012-11-01

As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave-particle interactions and the resulting precipitation produces auroral conductance. Realistic electron loss is thus important for modeling the magnetosphere - ionosphere (M-I) coupling and the degree of plasma sheet electron penetration into the inner magnetosphere. In order to evaluate the significance of electron loss, we used the Rice Convection Model (RCM) coupled with a force-balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self-consistent electric and magnetic field. We used different magnitudes of i) strong pitch angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that electron pressure under the MLT rate is larger compared to the strong rate inside L ∼ 12 RE. The dawn-dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. High-energy electrons inside L ∼ 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Under the MLT rate, the remaining electrons cause higher conductance at lower latitudes; thus after a convection enhancement, the shielding of the convection electric field is less efficient, and as a result, the ion plasma sheet penetrates further earthward into the inner magnetosphere than under the strong rate.

Observation and theory of the barium releases from the CRRES satellite

NASA Technical Reports Server (NTRS)

Bernhardt, P. A.; Huba, J. D.; Scales, W. A.; Wescott, E. M.; Stenbaek-Nielsen, H. C.

1992-01-01

The relationship between releases of barium from the NASA Combined Release and Radiation Effects Satellite (CRRES) and enhanced auroral activity is discussed with reference to observational data. Barium releases were conducted at a variety of altitudes and injection velocities, and plasma irregularities are reported as a result of the interactions. Auroral activity increased within 5 min of each release, and references are made to the effects on diamagnetic cavities, bulk ion motion, and stimulated electron and ion precipitation. Artificially created structured diamagnetic cavities are noted for each release, plasma waves are generated by the high-speed ion clouds, and enhanced ionization is found in the critical ionization-velocity process. Barium releases are effective in stimulating electron precipitation, and the observed irregularities are related to cycloid bunching of the initial ion distributions.

The polar caps

NASA Astrophysics Data System (ADS)

Akasofu, S.-I.

1985-12-01

According to the most common definition, the 'polar cap' is the region bounded by the average or statistical auroral oval. Studies of the effects of the interplanetary magnetic field (IMF) on various upper atmospheric phenomena are reviewed. The Antarctic region and the Arctic region represent an area for such investigations. Particular attention is given in this paper to those observations in the highest latitude region which provide some information concerning corresponding changes of the internal structure of the magnetosphere. A definition and working definition of the polar cap are considered along with the IMF and magnetospheric models, the entry of solar energetic electrons, statistical studies regarding the aurora, individual events, polar cap arcs, the cusp aurora, auroral electron precipitation, convection, ionospheric currents and field-aligned currents, the ionosphere, the thermosphere, polar rain, polar wind, and hopping motions of heavy ions.

Exploring the relative boundaries of the patchy pulsating aurora

NASA Astrophysics Data System (ADS)

Carlisle, E.; Donovan, E.; Jackel, B. J.

2017-12-01

Pulsating aurora is a common auroral feature that occurs most frequently on the nightside, in the equatorward part of the auroral oval. It is caused by pitch angle scattering of electrons due to wave-particle interactions near the equatorial plane. As such, observations of pulsating aurora provide information about the distribution of the plasma waves in the magnetosphere. Anecdotal evidence suggests that pulsating aurora occur equatorward of the proton aurora, and hence in the largely dipolar region at or inside the inner edge of the plasma sheet. Here we present results of a statistical survey of photometer observations of proton aurora and simultaneous all-sky imager observations of electron aurora. Our objective is to provide a definitive statement regarding the location of pulsating aurora relative to the proton aurora.

FAST satellite observations of large-amplitude solitary structures

NASA Astrophysics Data System (ADS)

Ergun, R. E.; Carlson, C. W.; McFadden, J. P.; Mozer, F. S.; Delory, G. T.; Peria, W.; Chaston, C. C.; Temerin, M.; Roth, I.; Muschietti, L.; Elphic, R.; Strangeway, R.; Pfaff, R.; Cattell, C. A.; Klumpar, D.; Shelley, E.; Peterson, W.; Moebius, E.; Kistler, L.

We report observations of “fast solitary waves” that are ubiquitous in downward current regions of the mid-altitude auroral zone. The single-period structures have large amplitudes (up to 2.5 V/m), travel much faster than the ion acoustic speed, carry substantial potentials (up to ∼100 Volts), and are associated with strong modulations of energetic electron fluxes. The amplitude and speed of the structures distinguishes them from ion-acoustic solitary waves or weak double layers. The electromagnetic signature appears to be that of an positive charge (electron hole) traveling anti-earthward. We present evidence that the structures are in or near regions of magnetic-field-aligned electric fields and propose that these nonlinear structures play a key role in supporting parallel electric fields in the downward current region of the auroral zone.

Freja Studies of the Current-Voltage Relation in Substorm-Related Events

NASA Technical Reports Server (NTRS)

Olsson, A.; Andersson, Laila; Eriksson, A. I.; Clemmons, J.; Erlandsson, R. E.; Reeves, G.; Hughes, T.; Murphee, J. S.

2000-01-01

Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j(sub II) = KV between field-aligned current density j(sub II) and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet magnetospheric situations, with acceleration voltages V approx. less than 5 kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study substorm related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even i n these conditions, although with values of the field aligned K lower than previously reported (1-5 x 10(exp 11 S/sq m). This can be explained by lower densities and higher characteristic electron energies in the magnetospheric source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study, where the spectra of precipitating electrons --were indirectly inferred by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and magnetospheric conditions.

Freja studies of the current-voltage relation in substorm-related events

NASA Astrophysics Data System (ADS)

Olsson, A.; Andersson, L.; Eriksson, A. I.; Clemmons, J.; Erlandsson, R. E.; Reeves, G.; Huges, T.; Murphee, J. S.

1998-03-01

Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j∥=KV between field-aligned current density j∥ and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet magnetospheric situations, with acceleration voltages V<~5kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study substorm related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even in these conditions, although with values of the field aligned K lower than previously reported (1-5×10-11S/m2). This can be explained by lower densities and higher characteristic electron energies in the magnetospheric source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study [Olsson et al., 1996 b], where the spectra of precipitating electrons were indirectly infered by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and magnetospheric conditions.

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 generated was lower than with no plasma present. Plasma diagnostics established the plasma frequency on the order of 150-300MHz and electron density ranging from ~1014-1015m-3, whilst the cyclotron frequency of the electrons within the Penning trap was 5.87GHz giving fce/fpe ~19-40, comparable to the auroral density cavity. Numerical simulations coinciding with this part of the experimental research program are currently being carried out using the VORPAL code. Details of these simulations will be presented in a separate paper [Speirs et al] at this meeting. McConville SL et al 2008, Plasma Phys. Control. Fusion, 50, 074010 Ronald et al 2011, Plasma Phys. Control. Fusion, 53, 074015 Bingham R and Cairns RA, 2002, Phys. Scr., T98, 160-162 Ergun RE et al, 1998, Geophys. Res. Lett., 25, 2061 Gurnett DA et al, 1974, J. Geophys. Res., 79, 4227-4238 Cairns RA et al, 2011, Phys. Plasmas, 18, 022902 Gillespie KM et al, 2008, Plasma Phys. Control. Fusion, 50, 124038 Speirs et al 2010, Phys. Plasmas, 17, 056501 Vorgul et al 2011, Phys. Plasmas, 18, 056501 McConville SL et al 2011, Plasma Phys. Control. Fusion, 53, 124020

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 precipitation and aurora appearing in this western and poleward protion of the bulge. The convection reversal is sharp in the west of bulge and surge horn sectors, and near the high-latitude boundary of the upward region 1, with a near stagnation region often extending over a large interval of latitude. In the eastern bulge and east of bulge sectors, the region 1 and 2 FACs are located in the sunward convection region, while a spikelike electric field occasionally appears poleward of the aurora but usually not associated with a pair of FAC sheets. In the eastern bulge, magnetic field data show complicated FAC distributions which correspond to current segments and filamentary currents.

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.

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.

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

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.

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.

Generation of Traveling Atmospheric Disturbances During a Pulsating Geomagnetic Storm

NASA Astrophysics Data System (ADS)

Gardner, L. C.; Schunk, R. W.

2009-12-01

Traveling Atmospheric Disturbances (TAD’s) are studied with a 3-D high-resolution (1°x3°) global thermosphere/ionosphere model to determine the importance of the high-latitude production mechanisms contained in the model. The possible production mechanisms are the oval size, the precipitating electron characteristic energy and energy flux, and the cross polar cap potential. The production mechanisms are pulsed at a one-hour period, as was observed in a recent long-duration geomagnetic storm. With auroral pulsation a TAD is generated that propagates equatorward away from the high-latitude auroral oval, depositing energy and transporting mass and momentum into the mid- and low-latitude thermosphere system. Depending on the amount of energy input into the high-latitude auroral zone, the TAD may travel to mid-latitudes, low-latitudes, or if sufficient energy is deposited, the TAD may even propagate across the opposite pole. These and other aspects of TAD generation will be shown.

Plasma flow disturbances in the magnetospheric plasma sheet during substorm activations

NASA Astrophysics Data System (ADS)

Kozelova, T. V.; Kozelov, B. V.; Turyanskii, V. A.

2017-11-01

We have considered variations in fields and particle fluxes in the near-Earth plasma sheet on the THEMIS-D satellite together with the auroral dynamics in the satellite-conjugate ionospheric part during two substorm activations on December 19, 2014 with K p = 2. The satellite was at 8.5 R E and MLT = 21.8 in the outer region of captured energetic particles with isotropic ion fluxes near the convection boundary of electrons with an energy of 10 keV. During substorm activations, the satellite recorded energetic particle injections and magnetic field oscillations with a period of 90 s. In the satellite-conjugate ionospheric part, the activations were preceded by wavelike disturbances of auroral brightness along the southern azimuthal arc. In the expansion phase of activations, large-scale vortex structures appeared in the structure of auroras. The sudden enhancements of auroral activity (brightening of arcs, auroral breakup, and appearance of NS forms) coincided with moments of local magnetic field dipolarization and an increase in the amplitude Pi2 of pulsations of the B z component of the magnetic field on the satellite. Approximately 30-50 s before these moments, the magnetosphere was characterized by an increased rate of plasma flow in the radial direction, which initiated the formation of plasma vortices. The auroral activation delays relative to the times when plasma vortices appear in the magnetosphere decreased with decreasing latitude of the satellite projection. The plasma vortices in the magnetosphere are assumed to be responsible for the observed auroral vortex structures and the manifestation of the hybrid vortex instability (or shear flow ballooning instability) that develops in the equatorial magnetospheric plane in the presence of a shear plasma flow in the region of strong pressure gradients in the Earthward direction.

Hemispheric Asymmetries in Substorm Recovery Time Scales

NASA Technical Reports Server (NTRS)

Fillingim, M. O.; Chua, D H.; Germany, G. A.; Spann, James F.

2009-01-01

Previous statistical observations have shown that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) are roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). This suggests that auroral substorms in the northern and southern hemispheres develop asymmetrically during solstice conditions with substorms lasting longer in the winter (dark) hemisphere than in the summer (sunlit) hemisphere. Additionally, this implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. This result, coupled with previous observations that have shown that auroral activity is more common when the ionosphere is in darkness and is suppressed when the ionosphere is in daylight, strongly suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. Here, we extend our earlier work by statistically analyzing the recovery time scales for a large number of substorms observed in the conjugate hemispheres simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. Our current results are consistent with previous observations. The recovery time scales are observed to be longer in the winter (dark) hemisphere while the auroral activity has a shorter duration in the summer (sunlit) hemisphere. This leads to an asymmetric energy input from the magnetosphere to the ionosphere with more energy being deposited in the winter hemisphere than in the summer hemisphere.

Field-aligned Currents Induced by Electrostatic Polarization at the Ionosphere: Application to the Poleward Boundary Intensification (PBI) of Auroral Emission

NASA Astrophysics Data System (ADS)

Ohtani, S.; Yoshikawa, A.

2016-12-01

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 auroral 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 auroral oval. We propose that the ionospheric currents driven by the associated electric field diverges/converges at the poleward boundary of the auroral 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 electron precipitation, which may cause auroral 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 auroral 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.

Research activities on Antarctic middle atmosphere by JARE 25th team

NASA Technical Reports Server (NTRS)

Hirasawa, T.; Eiwasaka, Y. AFTANAKA, M. agfujii, r.0 typ; Eiwasaka, Y. AFTANAKA, M. agfujii, r.0 typ

1985-01-01

The Antarctic Middle Atmosphere (AMA)-Japan research project was set about by the JARE (Japan Antarctic Research Expedition) 23rd team in 1982, and since then the JARE-24th and JARE-25th teams have been continuing reseach on the Antarctic Middle Atmosphere. Results gained by JARE-25th team members who are now working at Syowa Station (69.99 deg S, 39.35 deg E), Antarctica are presented. In their activities satellite measurements (Exos-C) and rocket soundings are used. Three rockets of the S310 type were launched at Syowa Station (Geomagnetic Latitude = 69.9 deg S) for the purpose of directly observing the electron density, ionospheric temperature, auroral patterns and luminosity in situ. Vertical profiles of electron density and auroral emission 4278A measured by three rockets are compared.

Effects of eletron heating on the current driven electrostatic ion cyclotron instability and plasma transport processes along auroral field lines

NASA Technical Reports Server (NTRS)

Ganguli, Supriya B.; Mitchell, Horace G.; Palmadesso, Peter J.

1988-01-01

Fluid simulations of the plasma along auroral field lines in the return current region have been performed. It is shown that the onset of electrostatic ion cyclotron (EIC) related anomalous resistivity and the consequent heating of electrons leads to a transverse ion temperature that is much higher than that produced by the current driven EIC instability (CDICI) alone. Two processes are presented for the enhancement of ion heating by anomalous resistivity. The anomalous resistivity associated with the turbulence is limited by electron heating, so that CDICI saturates at transverse temperature that is substantially higher than in the absence of resistivity. It is suggested that this process demonstrates a positive feedback loop in the interaction between CDICI, anomalous resistivity, and parallel large-scale dynamics in the topside ionosphere.

What can we learn from the auroral footprints of the Jovian moons? (Invited)

NASA Astrophysics Data System (ADS)

Bonfond, B.

2010-12-01

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 auroral 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 electron acceleration processes. The altitude of the Io footprint has also been used to infer the typical energy of the impinging electrons. 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 auroral electrons. 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.

Farley-Buneman Instability Effects on the Ionosphere and Thermosphere

NASA Astrophysics Data System (ADS)

Liu, J.; Wang, W.; Oppenheim, M. M.; Dimant, Y. S.; Wiltberger, M. J.; Merkin, V. G.

2016-12-01

We have recently implemented a newmodule that includes both the anomalous electron heating and the electron-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 130km altitude, and their magnitudes often exceed auroral precipitation heating in the TIEGCM. The induced changes in E region electron temperature in the auroral 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. Thermosphere wind and composition changes associated with FBI will also be investigated. This investigation demonstrates how researchers can add the important effects of the FBI to magnetosphere-ionosphere-thermosphere models and simulators.

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.

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.

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.

Extreme Spacecraft Charging in Polar Low Earth Orbit

NASA Technical Reports Server (NTRS)

Colson, Andrew D.; Minow, Joseph I.; Parker, L. Neergaard

2012-01-01

Spacecraft in low altitude, high inclination (including sun -synchronous) orbits are widely used for remote sensing of the Earth fs 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 episodically charge to frame potentials in the kilovolt range when exposed to space weather environments characterized by a high flux of energetic (approx.10 fs kilovolt) electrons in regions of low background plasma density. Auroral charging conditions are similar in some ways to the space weather conditions in geostationary orbit responsible for spacecraft charging to kilovolt levels. We first review the physics of space environment 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. Finally, a set of extreme DMSP charging events are described varying in maximum negative frame potential from approx.0.6 kV to approx.2 kV, focusing on the characteristics of the charging events that are of importance both to the space system designer and to spacecraft operators. The goal of the presentation is to bridge the gap between scientific studies of auroral charging and the need for engineering teams to understand how space weather impacts both spacecraft design and operations for vehicles on orbital trajectories that traverse auroral charging environments.

Intense uniform precipitation of low-energy electrons over the polar cap

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

Meng, C.; Kroehl, H.W.

1977-06-01

Analysis of precipitating electron data from the Defense Meteorological Satellite Program (DMSP) revealed significant enhancements (as large as two orders of magnitude) over the quiet time level of the low-energy electron flux over the polar cap during magnetic storms in September and October 1974. Strong asymmetry between the two polar caps was observed, and it may indicate that these electrons are of interplanetary (i.e., solar) origin and that their entry is influenced by the interplanetary magnetic field as illustrated by Yeager and Frank (1976) and Fennell et al., (1975). Energy spectra showing the spatial and temporal variations of the phenomenamore » are presented. There also is a region between the equatorward edge of the polar cap enhancement and the poleward edge of the evening auroral precipitation in which the electron flux drops down to the background level. If the observed intense polar cap precipitation is indeed of interplanetary origin, this void region implies that the poleward boundary of the auroral precipitation does not coincide with the equatorward boundary of the open field lines and that their separation cna be as wide as a few degrees in latitude.« less

RX and Z Mode Growth Rates and Propagation at Cavity Boundaries

NASA Astrophysics Data System (ADS)

Mutel, R. L.; Christopher, I. W.; Menietti, J. D.; Gurnett, D. A.; Pickett, J. S.; Masson, A.; Fazakerley, A.; Lucek, E.

Recent Cluster WBD observations in the Earth's auroral acceleration region have detected trapped Z mode auroral kilometric radiation while the spacecraft were entering a deep density cavity. The Z mode has a clear cutoff at the local upper hybrid resonance frequency, while RX mode radiation is detected above the RX mode cutoff frequency. The small gap between the upper hybrid resonance and the RX mode cutoff frequencies is proportional to the local electron density as expected from cold plasma theory. The width of the observed gap provides a new sensitive measure of the ambient electron density. In addition, the relative intensities of RX and Z mode radiation provide a sensitive probe of the plasma β = Ω_pe /Ω_ce at the source since the growth rates, although identical in form, have different ranges of allowed resonant radii which depend on β. In particular, the RX mode growth is favored for low β, while the Z mode is favored at higher β. The observed mode intensities and β's appear to be consistent with this model, and favor generation of Z mode at the source over models in which Z mode is generated by mode-conversion at cavity boundaries. These are the first multi-point direct measurements of mode-specific AKR propagation in the auroral acceleration region of any planet.

Generation of auroral kilometric and Z mode radiation by the cyclotron maser mechanism

NASA Technical Reports Server (NTRS)

Omidi, N.; Gurnett, D. A.; Wu, C. S.

1984-01-01

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 auroral kilometric radiation, that both the upgoing and the downgoing electrons are unstable and can give rise to this radiation's growth. The magnitudes of the growth rates for both the upgoing and downgoing auroral 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 electron distribution is unstable and the growth rates are large enough to account for the observed intensities.

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.

A Pulsating X-Ray Hot Spot on Jupiter

NASA Technical Reports Server (NTRS)

Gladstone, G. R.; Waite, J. H.; Grodent, D. C.; Crary, F. J.; Elsner, R. F.; Weisskopf, M. C.; Majeed, T.; Lewis, W. S.; Jahn, J.-M.; Bhardwaj, A.;

Improving the Ionospheric Auroral Conductance in a Global Ring Current Model and the Effects on the Ionospheric Electrodynamics

NASA Astrophysics Data System (ADS)

Yu, Y.; Jordanova, V. K.; McGranaghan, R. M.; Solomon, S. C.

2017-12-01

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 auroral 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 electron transport code (GLOW) to more self-consistently compute the height-dependent electric conductivity, provided the auroral electron 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.

Nonlinear electron-acoustic rogue waves in electron-beam plasma system with non-thermal hot electrons

NASA Astrophysics Data System (ADS)

Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.

2014-11-01

The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, non-thermal hot electrons obeying a non-thermal distribution, an electron 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 electron beam and energetic population parameter are discussed. The results of the present investigation may be applicable in auroral zone plasma.

Effect of Precipitating Electrons on Stormtime Inner Magnetospheric Electric Fields during the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C. L.; Sazykin, S. Y.; Wolf, R.; Hecht, J. H.; Walterscheid, R. L.; Boyd, A. J.; Turner, D. L.

2015-12-01

We investigate how scattering of electrons by waves in the plasma sheet and plasmasphere affects precipitating energy flux distributions and how the precipitating electrons modify the ionospheric conductivity and electric potentials during the large 17 March 2013 magnetic storm. Of particular interest is how electron precipitation in the evening sector affects the development of the Sub-auroral Polarization Stream (SAPS) electric field that is observed at sub-auroral latitudes in that sector. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the stormtime precipitating electron distributions and the electric field. We use parameterized rates of whistler-generated electron 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. We compare simulated trapped and precipitating electron flux distributions with measurements from Van Allen Probes/MagEIS, POES/TED and MEPED, respectively, to validate the electron loss model. Ground-based (SuperDARN) and in-situ (Van Allen Probes/EFW) observations of electric fields are compared with the simulation results. We discuss the effect of precipitating electrons on the SAPS and inner magnetospheric electric field through the data-model comparisons.

Empirical STORM-E Model. [I. Theoretical and Observational Basis

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.; Xu, Xiaojing; Bilitza, Dieter; Mlynczak, Martin G.; Russell, James M., III

2013-01-01

Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region peak electron densities. The empirical model is called STORM-E and will be incorporated into the 2012 release of the International Reference Ionosphere (IRI). The proxy for characterizing the E-region response to geomagnetic forcing is NO+(v) volume emission rates (VER) derived from the TIMED/SABER 4.3 lm channel limb radiance measurements. The storm-time response of the NO+(v) 4.3 lm VER is sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO+(v) 4.3 lm VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. Part II of this series describes the explicit development of the empirical storm-time correction factor for E-region peak electron densities, and shows comparisons of E-region electron densities between STORM-E predictions and incoherent scatter radar measurements. In this paper, Part I of the series, the efficacy of using SABER-derived NO+(v) VER as a proxy for the E-region response to solar-geomagnetic disturbances is presented. Furthermore, a detailed description of the algorithms and methodologies used to derive NO+(v) VER from SABER 4.3 lm limb emission measurements is given. Finally, an assessment of key uncertainties in retrieving NO+(v) VER is presented

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.

Probing galaxy growth through metallicity scaling relations over the past 12 Gyr of cosmic history

NASA Astrophysics Data System (ADS)

Sanders, Ryan; MOSDEF team

2018-01-01

A primary goal of galaxy evolution studies is to understand the processes governing the growth of the baryonic content of galaxies over cosmic history. Observations of galaxy metallicity scaling relations and their evolution with redshift, in combination with chemical evolution models, provide unique insight into the interplay between star formation, gas accretion, and feedback/outflows. I present measurements of the stellar mass-gas phase metallicity relation and its evolution over the past 12 Gyr from z~0 to z~3.5, utilizing data from the Mosfire Deep Evolution Field survey that uniquely provides rest-frame optical spectra of >1000 uniformly-selected galaxies at z=1.3-3.8. We find evolution towards lower metallicity at fixed stellar mass with increasing redshift that is consistent with current cosmological simulations including chemical evolution, with a large evolution of ~0.3 dex from z~0 to z~2.5 and minor evolution of <0.1 dex from z~2.5 to z~3.5. We unambiguously confirm the existence of star-formation rate dependence of the mass-metallicity relation at high redshift for the first time. A clear view of cosmic chemical evolution requires accounting for systematic biases in galaxy metallicity measurements at both low and high redshifts. We use a set of empirically-based models to correct for diffuse ionized gas contamination that biases metallicity estimates from z~0 global galaxy spectra. Evolving properties of ionized gas such as electron density, ionization parameter, hardness of the ionizing spectrum, and chemical abundance patterns may render locally-calibrated metallicity estimators unreliable at high redshifts. Using strong-line ratios alone, it is extremely difficult to break degenerate solutions between pure metallicity evolution and additional evolution of the ionization parameter and/or shape of the ionizing spectrum. Temperature-sensitive auroral-line measurements provide a way to directly and independently measure metallicities, breaking these degeneracies. We present measurements of auroral [OIII]4363 and direct-method metallicities at z>2, and discuss the potential of current and next-generation observational facilities to obtain statistical auroral-line samples at high redshifts.

Electron Driven Processes in Atmospheric Behaviour

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Teubner, P. J. O.

2006-11-01

Electron 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 electron impact cross sections, are required for such calculations. Five electron-driven processes are considered: auroral and dayglow emissions, the reduction of atmospheric electron 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.

Double layers in expanding plasmas and their relevance to the auroral plasma processes

NASA Astrophysics Data System (ADS)

Singh, Nagendra; Khazanov, George

2003-04-01

When a dense plasma consisting of a cold and a sufficiently warm electron 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 electron 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 auroral acceleration of electrons 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 electron 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 electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron 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 electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two-stream interactions on the high-potential side of the RFS generate electron-acoustic waves, which evolve into electron phase-space holes. The ion population originating from the low-potential side and trapped by the RFS is energized by the e-i and i-i instabilities and it eventually precipitates into the high-potential plasma along with an electron beam. Applications of these findings to the auroral plasma physics are discussed.

Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

NASA Technical Reports Server (NTRS)

Singh, Nagendra; Khazanov, George

2003-01-01

When a dense plasma consisting of a cold and a sufficiently warm electron 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 electron 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 auroral acceleration of electrons 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 electron 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 electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron 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 electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two-stream interactions on the high-potential side of the RFS generate electron-acoustic waves, which evolve into electron phase-space holes. The ion population originating from the low-potential side and trapped by the RFS is energized by the e-i and i-i instabilities and it eventually precipitates into the high-potential plasma along with an electron beam. Applications of these findings to the auroral plasma physics are discussed.

Rocket measurements of electron temperature in the E region

NASA Technical Reports Server (NTRS)

Zimmerman, R. K., Jr.; Smith, L. G.

1980-01-01

The rocket borne equipment, experimental method, and data reduction techniques used in the measurement of electron temperature in the E region are fully described. Electron temperature profiles from one daytime equatorial flight and two nighttime midlatitude flights are discussed. The last of these three flights, Nike Apache 14.533, showed elevated E region temperatures which are interpreted as the heating effect of a stable auroral red arc.

Role of excited N2 in the production of nitric oxide

NASA Astrophysics Data System (ADS)

Campbell, L.; Cartwright, D. C.; Brunger, M. J.

2007-08-01

Excited N2 plays a role in a number of atmospheric processes, including auroral and dayglow emissions, chemical reactions, recombination of free electrons, and the production of nitric oxide. Electron impact excitation of N2 is followed by radiative decay through a series of excited states, contributing to auroral and dayglow emissions. These processes are intertwined with various chemical reactions and collisional quenching involving the excited and ground state vibrational levels. Statistical equilibrium and time step atmospheric models are used to predict N2 excited state densities and emissions (as a test against previous models and measurements) and to investigate the role of excited nitrogen in the production of nitric oxide. These calculations predict that inclusion of the reaction N2[A3Σu +] + O, to generate NO, produces an increase by a factor of up to three in the calculated NO density at some altitudes.

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.

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.

Inverted-V events simultaneously observed with the Freja satellite and from the ground

NASA Astrophysics Data System (ADS)

Haerendel, G.; Frey, H. U.; Bauer, O. H.; Rieger, E.; Clemmons, J.; Boehm, M. H.; Wallis, D. D.; Lühr, H.

The paper reports data received from the Freja satellite during two passes over broad auroral arc systems or inverted-V events above Gillam/Manitoba when special wide-angle CCD cameras were operated at this location in addition to the CANOPUS network. Detailed comparisons of the visible structures with modulations of the primary electron fluxes are performed. Motions of this fine structures are interpreted in terms of high-altitude electric fields shielded from the lower ionosphere. Simultaneous readings of current density, accelerating voltage and energy flux, the latter determined both from particle and auroral brightness measurements, are found to be internally consistent. We calculate from these data the effective resistance encountered by the electric currents and find agreement with the kinetic theory of the mirror impedance, if we allow for substantial variations in density and energy of the source electrons in the magnetosphere.

Nitric oxide excited under auroral conditions: Excited state densities and band emissions

NASA Astrophysics Data System (ADS)

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

2000-09-01

Electron impact excitation of vibrational levels in the ground electronic state and nine excited electronic 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 electron impact excitation cross sections for NO were combined with a measured IBC II auroral secondary electron distribution, and the vibrational populations of 10 NO electronic states were determined under conditions of statistical equilibrium. This model predicts an extended vibrational distribution in the NO ground electronic state produced by radiative cascade from the seven higher-lying doublet excited electronic states populated by electron impact. In addition to significant energy storage in vibrational excitation of the ground electronic state, both the a 4Π and L2 Φ excited electronic states are predicted to have relatively high number densities because they are only weakly connected to lower electronic states by radiative decay. Fundamental mode radiative transitions involving the lowest nine excited vibrational levels in the ground electronic state are predicted to produce infrared (IR) radiation from 5.33 to 6.05 μm with greater intensity than any single NO electronic emission band. Fundamental mode radiative transitions within the a 4Π electronic state, in the 10.08-11.37 μm region, are predicted to have IR intensities comparable to individual electronic 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].

The reaction of N/2D/ with O2 as a source of O/1D/ atoms in aurorae

NASA Technical Reports Server (NTRS)

Rusch, D. W.; Sharp, W. E.; Gerard, J.-C.

1978-01-01

The source of O(1D) atoms in the auroral ionosphere is investigated using sounding rocket data. Previously, it has been shown that the conventional sources of O(1D) atoms in the aurora, dissociative recombination of O2(plus) and electron impact excitation of atomic oxygen, fail to explain the measured 6300 A volume emission rate profile. It is suggested that the atom-atom interchange reaction of N(2D) with O2 can be the major source of auroral 6300 A emission if O(1D) is created with high efficiency.

The precipitation of energetic heavy ions into the upper atmosphere of Jupiter

NASA Technical Reports Server (NTRS)

Horanyi, M.; Cravens, T. E.; Waite, J. H., Jr.

1987-01-01

Evidence for auroral particle precipitation at Jupiter was provided by the ultraviolet spectrometers onboard the Voyagers 1 and 2 spacecraft and by the International Ultraviolet Explorer (IUE). Magnetospheric measurements made by instruments onboard the Voyager spacecraft show that energetic sulfur and oxygen ions are precipitating into the upper atmosphere of Jupiter. A theoretical model has been constructed describing the interaction of precipitating oxygen with the Jovian atmosphere. The auroral energy is deposited in the atmosphere by means of ionization, excitation, and dissociation and heating of the atmospheric gas. Energetic ion and electron precipitation are shown to have similar effects on the atmosphere and ionosphere of Jupiter.

Field-aligned currents observed in the vicinity of a moving auroral arc

NASA Technical Reports Server (NTRS)

Goertz, C. K.; Bruening, K.

1984-01-01

The sounding rocket Porcupine F4 was launched into an auroral 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 electron 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.

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.

Wave and Particle Interactions in the High and Low-Altitude Auroral Region During Rising Solar Activity

NASA Technical Reports Server (NTRS)

Gurnett, Donald A.; Menietti, J. D.

2003-01-01

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 electron cyclotron waves observed by the Polar spacecraft throughout the auroral 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 auroral 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.

Effect of electron beam on the properties of electron-acoustic rogue waves

NASA Astrophysics Data System (ADS)

El-Shewy, E. K.; Elwakil, S. A.; El-Hanbaly, A. M.; Kassem, A. I.

2015-04-01

The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, Maxwellian hot electrons, an electron 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 electron and electron beam, relative cold electron temperature and relative beam temperature are discussed. The results of the present investigation may be applicable in auroral zone plasma.

Detection of F-region electron density irregularities using incoherent-scatter radar

NASA Astrophysics Data System (ADS)

Gudivada, Krishna Prasad

Incoherent-scatter radar data from Poker Flat, Alaska has been used to determine size distributions of electron density structures in the evening time sector of the auroral zone. At high latitudes ionospheric plasma typically moves east-west with speeds of several hundred meters per second. Density irregularities that rapidly move through the radar beam are therefore observed as time-varying power fluctuations. The new phased array radar used for this study has been operated with several antenna directions with successive pulses transmitted in each direction. It is therefore possible to observe plasma Doppler velocities in multiple directions and determine the vector direction of the plasma motion. This near-simultaneous observation of the plasma velocity in conjunction with the electron density height profile data enable a new technique to determine the scale sizes of electron density fluctuations that move horizontally through the radar beam. The study focuses on the collision-less F-region ionosphere where the plasma drift is approximately constant with altitude. The experimental technique limits the range of scale sizes that may be studied to relatively large-scale sizes (i.e. greater than few tens of km). Results show that during magnetically disturbed conditions (Kp ≥ 4) when westward plasma velocities are relatively high (500-1000 m/s) the scale sizes of irregularities (often called plasma blobs) are in the range of 100-300 km and predominantly originate from the polar cap and are transported over long distances (˜1000 km) due to the long chemical recombination times (30-90 minutes). Some irregularities are caused by local auroral particle precipitation and have been identified with associated electron temperature enhancements. For cases of low magnetic activity (Kp ≤ 1), when the radar is located in a region of low plasma velocities (100-500 m/s) well south of the auroral oval (essentially a mid-latitude type ionosphere), the density distribution is always biased strongly toward small-scale sizes (less than 50 km).

Time development of high-altitude auroral acceleration region plasma, potentials, and field-aligned current systems observed by Cluster during a substorm

NASA Astrophysics Data System (ADS)

Hull, A. J.; Chaston, C. C.; Fillingim, M. O.; Mozer, F.; Frey, H. U.

2013-12-01

The auroral 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 auroral acceleration processes in turn accelerate and heat the plasma that ultimately leads to some of the most intense global substorm auroral 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 auroral 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 auroral acceleration processes and auroral 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 electrons 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 current systems was quite rapid, occurring in the span of a few minutes. These results suggest that the Alfvenic activity may be an important precursor and perhaps may be playing an essential role in the development of inverted-V arc systems that form during substorms.

Alfvén Waves and the Aurora (Hannes Alfvén Medal Lecture)

NASA Astrophysics Data System (ADS)

Lysak, Robert

2015-04-01

The most compelling visual evidence of plasma processes in the magnetosphere of Earth as well as the other magnetized planets is the aurora. Over 40 years of research have indicated that the aurora is a consequence of the acceleration of charged particles toward the neutral atmosphere, where the excitation of neutral atoms and their subsequent relaxation to the ground state produces the auroral light. Much of this acceleration can be described by acceleration in a quasi-static electric field parallel to the geomagnetic field, producing nearly monoenergetic beams of electrons. While a variety of quasi-static models to describe such parallel electric fields have been developed, the dynamics of how these fields evolve is still an open question. Satellite measurements have indicated that a primary source of energy to support these fields is the Poynting flux associated with shear Alfvén waves propagating along auroral field lines. These Alfvén waves are generated in the magnetosphere and reflect from the ionosphere. On closed field lines, Alfvén waves bouncing between conjugate ionospheres produce field line resonances that have be observed both in space and by ground magnetometers. However, some auroral emissions do not follow this scenario. In these cases, the accelerated electrons are observed to have a broad energy spectrum, rather than a monoenergetic peak. Such a spectrum is suggestive of a time-dependent acceleration process that operates on a time scale of a few seconds, comparable to the electron transit time across the acceleration region. While field line resonances have a time scale on the order of minutes, waves with periods of a few seconds can be produced by partial reflections in the Ionospheric Alfvén Resonator, a resonant cavity formed by the rapid decrease of the plasma density and increase of the Alfvén speed above the ionosphere. In order to develop a parallel electric field that can accelerate auroral particles, these Alfvén waves must develop small spatial scales, where MHD theory breaks down. In this regime, the waves are called kinetic Alfvén waves. These small scales can be produced most simply be phase mixing, although ionospheric feedback and nonlinear effects may also be important. Since kinetic Alfvén waves require perpendicular wavelengths the order of a few kilometers, this model also provides a natural explanation of the narrow scales of discrete auroral arcs. These interactions between magnetosphere and ionosphere and the development of parallel electric fields have been described by means of numerical simulations that serve to illustrate these complex processes.

Applications of a time-dependent polar ionosphere model for radio modification experiments

NASA Astrophysics Data System (ADS)

Fallen, Christopher Thomas

A time-dependent self-consistent ionosphere model (SLIM) has been developed to study the response of the polar ionosphere to radio modification experiments, similar to those conducted at the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. SCIM solves the ion continuity and momentum equations, coupled with average electron and ion gas energy equations; it is validated by reproducing the diurnal variation of the daytime ionosphere critical frequency, as measured with an ionosonde. Powerful high-frequency (HF) electromagnetic waves can drive naturally occurring electrostatic plasma waves, enhancing the ionospheric reflectivity to ultra-high frequency (UHF) radar near the HF-interaction region as well as heating the electron gas. Measurements made during active experiments are compared with model calculations to clarify fundamental altitude-dependent physical processes governing the vertical composition and temperature of the polar ionosphere. The modular UHF ionosphere radar (MUIR), co-located with HAARP, measured HF-enhanced ion-line (HFIL) reflection height and observed that it ascended above its original altitude after the ionosphere had been HF-heated for several minutes. The HFIL ascent is found to follow from HF-induced depletion of plasma surrounding the F-region peak density layer, due to temperature-enhanced transport of atomic oxygen ions along the geomagnetic field line. The lower F-region and topside ionosphere also respond to HF heating. Model results show that electron temperature increases will lead to suppression of molecular ion recombination rates in the lower F region and enhancements of ambipolar diffusion in the topside ionosphere, resulting in a net enhancement of slant total electron content (TEC); these results have been confirmed by experiment. Additional evidence for the model-predicted topside ionosphere density enhancements via ambipolar diffusion is provided by in-situ measurements of ion density and vertical velocity over HAARP made by a Defense Meteorological Satellite Program (DMSP) satellite.

Contamination and Micropropulsion Technology

DTIC Science & Technology

2012-07-01

23, 027101 (2011) Evaluation of active flow control applied to wind turbine blade section J. Renewable Sustainable Energy 2, 063101 (2010) Effect...field lines at high latitudes where solar wind electrons can readily access the upper atmosphere. The electron energy distribution in the auroral... slip behavior of n-hexadecane in large amplitude oscillatory shear flow via nonequilibrium molecular dynamic simulation J. Chem. Phys. 136, 104904

Predicting Electron Population Characteristics in 2-D Using Multispectral Ground-Based Imaging

NASA Astrophysics Data System (ADS)

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

2018-01-01

Ground-based imaging and in situ sounding rocket data are compared to electron transport modeling for an active inverted-V type auroral event. The Ground-to-Rocket Electrodynamics-Electrons Correlative Experiment (GREECE) mission successfully launched from Poker Flat, Alaska, on 3 March 2014 at 11:09:50 UT and reached an apogee of approximately 335 km over the aurora. Multiple ground-based electron-multiplying charge-coupled device (EMCCD) imagers were positioned at Venetie, Alaska, and aimed toward magnetic zenith. The imagers observed the intensity of different auroral emission lines (427.8, 557.7, and 844.6 nm) at the magnetic foot point of the rocket payload. Emission line intensity data are correlated with electron characteristics measured by the GREECE onboard electron spectrometer. A modified version of the GLobal airglOW (GLOW) model is used to estimate precipitating electron characteristics based on optical emissions. GLOW predicted the electron population characteristics with 20% error given the observed spectral intensities within 10° of magnetic zenith. Predictions are within 30% of the actual values within 20° of magnetic zenith for inverted-V-type aurora. Therefore, it is argued that this technique can be used, at least in certain types of aurora, such as the inverted-V type presented here, to derive 2-D maps of electron characteristics. These can then be used to further derive 2-D maps of ionospheric parameters as a function of time, based solely on multispectral optical imaging data.

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.

Auroral Acceleration, Solar Wind Driving, and Substorm Triggering (Invited)

NASA Astrophysics Data System (ADS)

Newell, P. T.; Liou, K.

2010-12-01

We use a data base of 4861 substorms identified by global UV images to investigate the substorm cycle dependence of various types of aurora, and to obtain new results on substorm triggering by external driving. Although all types of aurora increase at substorm onset, broadband (Alfvénic) aurora shows a particular association with substorms, and, especially, substorm onset. While diffuse electron and monoenergetic auroral precipitating power rises by 79% and 90% respectively following an onset, broadband aurora rises by 182%. In the first 10-15 minutes following onset, the power associated with Alfvénic acceleration is comparable to monoenergetic acceleration (also called “inverted-V” events). In general, this is not the case prior to onset, or indeed, during recovery. The rise time of the electron diffuse aurora following onset is much slower, about 50 minutes, and thus presumably extends into recovery. We also re-investigate the issue of solar wind triggering of substorms by considering not just changes in the solar wind prior to onset, but how the pattern of changes differs from random and comparable epochs. We verify that a preonset reduction of solar wind driving (“northward turning” in the simplest case of IMF Bz) holds for the superposed epoch mean of the ensemble. Moreover, this reduction is not the result of a small number of substorms with large changes. The reduction starts about 20 min prior to substorm onset, which, although a longer delay than previously suggested, is appropriate given the various propagation time delays involved. Next, we compare the IMF to random solar wind conditions. Not surprisingly, solar wind driving prior to onset averages somewhat higher than random. Although about a quarter of substorms occur for steady northward IMF conditions, more general coupling functions such as the Kan-Lee electric field, the Borovosky function, or our dΦMP/dt, show very few substorms occur following weak dayside merging. We assembled a data base of solar wind times with slightly elevated conditions, chosen to resemble the integrated driving typical before substorm onsets, but otherwise randomly occuring. We looked at how the IMF subsequently changed after these random elevations, compared to the changes preceding substorms. It turns out that mere reversion to the mean leads to a “northward turning” after the imposed selection criterion end. Thus (slightly generalizing the view of Morley and Freeman), substorms require solar wind driving which produces dayside merging, but external triggering is probably insignificant.

Auroral Data Analysis

DTIC Science & Technology

1979-01-31

LT) sector, distinct and repeatable electron lair - and disceearrlrgos epetvI.Tepro tde tudinal distributions \\%ere observed as a function of substorm...of surface a ,wcond time by using the same procedure, Next the)’ were optical albedo and east-%est nonuniformities in precipitation grouped together

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.

Cleaning and activation of beryllium-copper electron multiplier dynodes.

NASA Technical Reports Server (NTRS)

Pongratz, M. B.

1972-01-01

Description of a cleaning and activation procedure followed in preparing beryllium-copper dynodes for electron multipliers used in sounding-rocket experiments to detect auroral electrons. The initial degreasing step involved a 5-min bath in trichloroethylene in an ultrasonic cleaner. This was followed by an ultrasonic rinse in methanol and by a two-step acid pickling treatment to remove the oxides. Additional rinsing in water and methanol was followed by activation in a stainless-steel RF induction oven.

Storm phase-partitioned rates and budgets of global Alfvénic energy deposition, electron precipitation, and ion outflow

NASA Astrophysics Data System (ADS)

Hatch, Spencer M.; LaBelle, James; Chaston, Christopher C.

2018-01-01

We review the role of Alfvén waves in magnetosphere-ionosphere coupling during geomagnetically active periods, and use three years of high-latitude FAST satellite observations of inertial Alfvén waves (IAWs) together with 55 years of tabulated measurements of the Dst index to answer the following questions: 1) How do global rates of IAW-related energy deposition, electron precipitation, and ion outflow during storm main phase and storm recovery phase compare with global rates during geomagnetically quiet periods? 2) What fraction of net IAW-related energy deposition, electron precipitation, and ion outflow is associated with storm main phase and storm recovery phase; that is, how are these budgets partitioned by storm phase? We find that during the period between October 1996 and November 1999, rates of IAW-related energy deposition, electron precipitation, and ion outflow during geomagnetically quiet periods are increased by factors of 4-5 during storm phases. We also find that ∼62-68% of the net Alfvénic energy deposition, electron precipitation, and ion outflow in the auroral ionosphere occurred during storm main and recovery phases, despite storm phases comprising only 31% of this period. In particular storm main phase, which comprised less than 14% of the three-year period, was associated with roughly a third of the total Alfvénic energy input and ion outflow in the auroral ionosphere. Measures of geomagnetic activity during the IAW study period fall near corresponding 55-year median values, from which we conclude that each storm phase is associated with a fraction of total Alfvénic energy, precipitation, and outflow budgets in the auroral ionosphere that is, in the long term, probably as great or greater than the fraction associated with geomagnetic quiescence for all times except possibly those when geomagnetic activity is protractedly weak, such as solar minimum. These results suggest that the budgets of IAW-related energy deposition, electron precipitation, and ion outflow are roughly equally partitioned by geomagnetic storm phase.

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.

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.

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.

Spacecraft Charging Hazards In Low-earth Orbit

NASA Astrophysics Data System (ADS)

Anderson, P. C.

The space environment in low-Earth orbit (LEO) has until recently been considered quite benign to high levels of spacecraft charging. However, it has been found that the DMSP spacecraft at 840 km can charge to very large negative voltages (up to - 2000 V) when encountering intense precipitating electron events (auroral arcs) while traversing the auroral zone. The occurrence frequency of charging events, defined as when the spacecraft charged to levels exceeding 100 V negative, was highly correlated with the 11-year solar cycle with the largest number of events occurring during solar minimum. This was due to the requirement that the background thermal plasma den- sity be low, at most 104 cm-2. During solar maximum, the plasma density is typically well above that level due to the solar EUV ionizing radiation, and although the oc- currence frequency of auroral arcs is considerably greater than at solar minimum, the occurrence of high-level charging is minimal. Indeed, of the over 1200 events found during the most recent solar cycle, none occurred during the last solar maximum. This has implications to a number of LEO satellite programs, including the International Space Station (ISS). The plasma density in the ISS orbit, at a much lower altitude than DMSP, is well above that at 840 km and rarely below 104 cm-2. However, in the wake of the ISS, the plasma density can be 2 orders of magnitude or more lower than the background density and thus conditions are ripe for significant charging effects. With an inclination of 51.6 degrees, the ISS does enter the auroral zone, particularly during geomagnetic storms and substorms when the auroral boundary can penetrate to very low latitudes. This has significant implications for EVA operations in the ISS wake.

Saturn aurora movies in visible and near-IR observed by Cassini ISS

NASA Astrophysics Data System (ADS)

Dyudina, U.; Wellington, D.; Ewald, S. P.; Ingersoll, A. P.; Porco, C.

2010-12-01

New 2009-2010 movies from the Cassini camera show Saturn’s auroral curtains move and change in both the northern and southern hemispheres. The observations reveal reddish color of the aurora observed in filters spanning different wavelengths. The aurora was detected in H-alpha (652-661 nm), red (574-724 nm), and broad-band infrared (668-833 nm) wavelengths, and also faintly in blue (405-505 nm) and green (507-632 nm) wavelengths. The prominent H-alpha line and the overall spectral shape agrees with predicted spectra for Saturnian auroras (Aguilar, 2008). Along with the spectra and brightness measurements, we will present two 400+ frame movies taken in the clear filter, one showing aurora in the northern hemisphere from October 5-9, 2009, and the other showing the aurora in the southern hemisphere, from June 26, 2010. These movies show the aurora varying dramatically with longitude and rotating together with Saturn. The main longitudinal structure of the aurora can persist for ~3 days, as seen on the repeated views of the same longitudes several Saturn rotations later. Besides the steady main structure, aurora may brighten suddenly on the timescales on the order of 10 minutes. Near the limb the height of the auroral curtains above its base can be measured; this height can reach more than 1200 km. The main auroral oval in the northern hemisphere appears near 75° latitude. The main auroral oval in the southern hemisphere appears near -72° latitude, with smaller instances of auroral activity near -75° and -77°. Reference: Aguilar, A., J. M. Ajello, R. S. Mangina, G. K. James, H. Abgrall, and E. Roueff, “The electron-excited middle UV to near IR spectrum of H2 : Cross-sections and transition probabilities”, Astrophys. J. Supp. Ser., 177 (2008).

In-depth analysis of the substorm recovery phase using electron and proton induced emissions from satellite observations

NASA Astrophysics Data System (ADS)

Bryant, Chad Richard

The aurora is a well known phenomenon in the night sky. The observer of the ground can only see part of what is truly happening. The active aurora observed from the ground relates in many cases to what is termed a magnetospheric substorm. Recent research has been involved in determining the cause of these events while other parts of the substorm have been little studied. While additional progress will be made through conventional analysis and observations of the substorm onset, new approaches are advantageous to clarify different aspects of magnetospheric substorms. Very little quantitative analysis has been completed on what is called the recovery phase. This dissertation represents an attempt to achieve the first in-depth quantitative study of the recovery phase. It will use conventional electron auroral observations as well as an exceptional new dataset courtesy of global images of proton aurora. To effectively exploit the observations, new analysis tools were developed to expand our understanding of the recovery phase. In this dissertation the use of the auroral substorm power was determined to be a good analytical method in working with magnetospheric substorms. The start and end of the recovery phase and the decay of the recovery phase were all analysed using this methodology. It was found that the decay of the recovery phase is exponential but can be interrupted by enhancements that are related to flows in the magnetotail and that the region from where the flow comes determines the optical signature that is seen in the ionosphere. An example shows how the unique proton dataset provides new possibilities for observations when compared to conventional electron auroral observations. All of these results provide valuable new insights into current magnetospheric substorm models.

Comparisons of Simulated and Observed Sub-Auroral Polarization Stream (SAPS) during the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C.; Sazykin, S. Y.; Wolf, R.; Anderson, P. C.

2016-12-01

Sub-Auroral 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 electron 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 electron 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 electron and proton contributions to the auroral 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.

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 midnight and dawn, simultaneous auroral observations by the HST reveal a close correlation between these dynamical magnetospheric events and dawn-side transient auroral brightenings. Likewise, many of the recurrent energetic neutral atom enhancements coincide closely with bursts of Saturn kilometric radiation, again suggesting a linkage with high latitude auroral processes. Finally, we will show some intriguing results of auroral movie sequences from the Cassini UVIS instrument with corresponding ring current movies from the Magnetospheric Imaging Instrument Ion and Neutral Camera (MIMI/INCA).

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 for dayside auroral oval to expand or contract, and the solar wind parameters (IMF Bx, By, Bz, speed, and pressure) associated with each interval (expansion, contraction, or stable and expanded).

Copernicus measurement of the Jovian Lyman-alpha emission and its aeronomical significance

NASA Technical Reports Server (NTRS)

Atreya, S. K.; Kerr, R. B.; Upson, W. L., II; Festou, M. C.; Donahue, T. M.; Barker, E. S.; Cochran, W. D.; Bertaux, J. L.

1982-01-01

It is pointed out that the intensity of the Lyman-alpha emission is a good indicator of the principal aeronomical processes on the major planets. The high-resolution ultraviolet spectrometer aboard the Orbiting Astronomical Observatory Copernicus was used in 1980 April and May to detect the Jovian Lyman-alpha emission by spectroscopically discriminating it from other Doppler shifted Lyman-alpha emissions such as those of the geocorona, and the interplanetary medium. Taking into consideration the reported emission data, it appears that an unusually large energy input due to the particle precipitation in the auroral region must have been responsible for the large observed Lyman-alpha intensity during the Voyager encounter. At most other times, the observed Jovian Lyman-alpha intensity can be explained, within the range of statistical uncertainty, by a model that takes into consideration the solar EUV flux, the solar Lyman-alpha flux, the high exospheric temperature, and the eddy diffusion coefficient without energy input from the auroral sources.

An S3-3 search for confined regions of large parallel electric fields

NASA Astrophysics Data System (ADS)

Boehm, M. H.; Mozer, F. S.

1981-06-01

S3-3 satellite passes through several hundred perpendicular shocks are searched for evidence of large, mostly parallel electric fields (several hundred millivolts per meter, total potential of several kilo-volts) in the auroral zone magnetosphere at altitudes of several thousand kilometers. The actual search criteria are that one or more E-field data points have a parallel component E sub z greater than 350 mV/m in general, or 100 mV/m for data within 10 seconds of a perpendicular shock, since double layers might be likely, in such regions. Only a few marginally convincing examples of the electric fields are found, none of which fits a double layer model well. From statistics done with the most unbiased part of the data set, upper limits are obtained on the number and size of double layers occurring in the auroral zone magnetosphere, and it is concluded that the double layers most probably cannot be responsible for the production of diffuse aurora or inverted-V events.

Data-driven local-scale modeling of ionospheric responses to auroral forcing using incoherent scatter radar and ground-based imaging measurements

NASA Astrophysics Data System (ADS)

Grubbs, G. A., II; Zettergren, M. D.; Samara, M.; Michell, R.; Hampton, D. L.; Lynch, K. A.; Varney, R. H.; Reimer, A.; Burleigh, M.

2017-12-01

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 auroral 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 electrons 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 electron transport code which produces auroral intensities, impact ionization, and thermal electron 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 electrons. 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-scale assimilative modeling approach where data-derived information will be fed back into the model to update the system state.

Analysis of data from the Lockheed Experiment on ATS-5. [magnetic storms and auroras in the ionosphere

NASA Technical Reports Server (NTRS)

Sharp, R. D.

1975-01-01

Satellite observations of auroral electrojets, electron fluxes, and magnetic storm activity are presented and discussed. Plasma-particle interactions are examined for the earth's magnetosphere, and data (i.e., magnetograms) of the satellite observations are analyzed.

Role of sudden commencements in triggering magnetospheric substorms. M.S. Thesis; [based on ATS 1 data

NASA Technical Reports Server (NTRS)

Newell, R. E.

1974-01-01

Sudden commencement events are examined in terms of available auroral-zone and low-latitude magnetic field, data, interplanetary plasma and magnetic field data, and magnetospheric electron flux and magnetic field data from the geostationary satellite ATS 1.

Coherent generation of the auroral kilometric radiation by nonlinear beatings between electrostatic waves

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

Pellat, R.; Roux, A.

1979-09-01

The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma is studied analytically. These waves, which are driven unstable by auroral beams of electrons, 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 » auroral 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

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.

Anomalous resistivity due to low-frequency turbulence. [of collisionless plasma with limited acceleration of high velocity runaway electrons

NASA Technical Reports Server (NTRS)

Rowland, H. L.; Palmadesso, P. J.

1983-01-01

Large amplitude ion cyclotron waves have been observed on auroral field lines. In the presence of an electric field parallel to the ambient magnetic field these waves prevent the acceleration of the bulk of the plasma electrons leading to the formation of a runaway tail. It is shown that low-frequency turbulence can also limit the acceleration of high-velocity runaway electrons via pitch angle scattering at the anomalous Doppler resonance.

Radiation induced conductivity of polycarbonate doped with different concentrations of aromatic hydrazone DEH

NASA Astrophysics Data System (ADS)

Vladimir, Saenko; Novikov, Lev; Tyutnev, Andrey

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 keV electrons prevailing in the hot magnetospheric plasma, including auroral radiation. Due to fluctuating fluxes of plasma electrons and especially of auroral electrons, 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 keV electrons. 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.

Generation of auroral kilometric radiation by a finite-size source in a dipole magnetic field

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

Burinskaya, T. M., E-mail: tburinsk@iki.rssi.ru; Shevelev, M. M.

2016-10-15

Generation, amplification, and propagation of auroral kilometric radiation in a narrow three-dimensional plasma cavity in which a weakly relativistic electron beam propagates is studied in the geometrical optics approximation. It is shown that the waves that start with a group velocity directed earthward and have optimal relation between the wave vector components determining the linear growth rate and the wave residence time inside the amplification region undergo the largest amplification. Taking into account the longitudinal velocity of fast electrons results in the shift of the instability domain toward wave vectors directed to the Earth and leads to a change inmore » the dispersion relation, due to which favorable conditions are created for the generation of waves with frequencies above the cutoff frequency for the cold background plasma at the wave generation altitude. The amplification factor for these waves is lower than for waves that have the same wave vectors but are excited by the electron beams with lower velocities along the magnetic field. For waves excited at frequencies below the cutoff frequency of the background plasma at the generation altitude, the amplification factor increases with increasing longitudinal electron velocity, because these waves reside for a longer time in the amplification region.« less

Cusp and LLBL as Sources of the Isolated Dayside Auroral Feature During Northward IMF

NASA Technical Reports Server (NTRS)

Chang, S.-W.; Gallagher, D. L.; Spann, J. F.; Mende, S. B.; Greenwald, R. A.; Newell, P. T.

2004-01-01

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 auroral oval and intruded farther poleward into the polar cap, and it showed longitudinal motions in response to IMF By variation. Intense magnetosheath-like electron 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 electrons 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 Auroral 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.

Two-dimensional quasineutral description of particles and fields above discrete auroral arcs

NASA Technical Reports Server (NTRS)

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

1985-01-01

Stationary hot and cool particle distributions in the auroral 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 electrons, 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.

Coherent generation of the terrestrial kilometric radiation by nonlinear beatings between electrostatic waves

NASA Technical Reports Server (NTRS)

Roux, A.; Pellat, R.

1978-01-01

The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma was studied. These waves, which are driven unstable by auroral beams of electrons, are shown to suffer a further geometrical amplification while they propagate towards resonances. Simultaneously, their group velocities tend to be aligned with the geomagnetic field. It is shown that the electrostatic energy tends to accumulate at, or near omega sub LH and omega sub UH, the local lower and upper hybrid frequencies. Due to this process, large amplitude electrostatic waves with very narrow spectra are observed near these frequencies at any place along the auroral field lines where intense beam driven instability takes place. These intense quasi-monochromatic electrostatic waves are shown to give rise to an intense electromagnetic radiation. Depending upon the ratio omega sub pe/omega sub ce between the electron plasma frequency and the electron gyro-frequency the electromagnetic wave can be radiated in the ordinary mode (at omega sub UH), or in the extraordinary (at 2 omega sub UH). As the ratio omega sub pe/omega sub ce tends to be rather small, it is shown that the most intense radiation should be boserved at 2 omega sub UH in the extraordinary mode.

The Visible Airglow Experiment - A review

NASA Technical Reports Server (NTRS)

Hays, Paul B.; Abreu, Vincent J.; Solomon, Stanley C.; Yee, Jeng-Hwa

1988-01-01

Contributions of the Visible Airglow Experiment (VAE) to the understanding of various airglow and auroral processes are reviewed. The impact of instrumental design and operation on the observations is discussed, and emphasis is placed on the relationship between observations and inversion for optical measurements of light emissions from a diffuse medium. VAE data are used to explain the physical mechanisms responsible for the production and destruction of excited species including O(+)(1P), O(1D), O(1S), N(2D), and Mg(+)2P1/2.

Development of the Near-Earth Magnetotail and the Auroral Arc Associated with Substorm Onset: Evidence for a New Model

NASA Astrophysics Data System (ADS)

Miyashita, Y.; Hiraki, Y.; Angelopoulos, V.; Ieda, A.; Machida, S.

2015-12-01

We have studied the time sequence of the development of the near-Earth magnetotail and the auroral 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 auroral development, linking them to magnetotail changes: the auroral fading, the initial brightening of an auroral 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 auroral initial brightening and ~1 min before the auroral fading. Ionospheric large-scale convection also became enhanced just before the auroral fading and before the auroral 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 auroral wave-like structure. Finally, the dipolarization began ~30 s before the auroral 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 auroral initial brightening and subsequent gradual growth of the auroral 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 auroral wave-like structure is further enhanced. When the instability grows sufficiently, the dipolarization and the auroral poleward expansion are initiated.

Electromagnetic Quasi-periodic Whistler-Mode Bursts during Ring Grazing Passes

NASA Astrophysics Data System (ADS)

Farrell, W. M.; Morooka, M. W.; Wahlund, J. E.; Kurth, W. S.; Hospodarsky, G.; MacDowall, R. J.; Mitchell, D. G.; Gurnett, D. A.; Krupp, N.; Roussos, E.; Kollmann, P.

2017-12-01

In the 2016-2017 time-frame, the Cassini spacecraft made a set of over 20 nearly identical Saturn orbital passes with closest approach at the outer edge of the F-ring. These passes are now called `Ring Grazing' orbits. During nearly every one of these orbits, quasi-periodic (QP) whistler-mode bursts were detected at mid-southern latitudes between -57o and -22o. During these ring grazing orbits, the spacecraft had an extended period of time where the trajectory 'hugged' the L 13 field line along its southern path when these bursts were detected. As such, we conclude that the 1 hr periodicity is not a spatial effect but a true temporal effect. In about 2/3 of the cases, there was wave activity observed above the local electron cyclotron frequency. We note that there have been previous reports of these QP whistler-mode burst in direct correlation with energetic auroral electron bursts, and we now also present the use of relativist electron cyclotron resonance theory to examine the wave-electron interactions. While in the past these waves have been considered a form of electrostatic auroral hiss, we suggest herein that the high energy of the electrons is more strongly coupled to the electromagnetic portion of the whistler-mode branch. In this presentation, we will provide more information on the wave character, and suggest the non-unique possibility that mode coupling is involved in creating emissions above the electron cyclotron frequency.

Investigation and Development of Data-Driven D-Region Model for HF Systems Impacts

NASA Technical Reports Server (NTRS)

Eccles, J. V.; Rice, D.; Sojka, J. J.; Hunsucker, R. D.

2002-01-01

Space Environment Corporation (SEC) and RP Consultants (RPC) are to develop and validate a weather-capable D region model for making High Frequency (HF) absorption predictions in support of the HF communications and radar communities. The weather-capable model will assimilate solar and earth space observations from NASA satellites. The model will account for solar-induced impacts on HF absorption, including X-rays, Solar Proton Events (SPE's), and auroral precipitation. The work plan includes: I . Optimize D-region model to quickly obtain ion and electron densities for proper HF absorption calculations. 2. Develop indices-driven modules for D-region ionization sources for low, mid, & high latitudes including X-rays, cosmic rays, auroral precipitation, & solar protons. (Note: solar spectrum & auroral modules already exist). 3. Setup low-cost monitors of existing HF beacons and add one single-frequency beacon. 4. Use PENEX HF-link database with HF monitor data to validate D-region/HF absorption model using climatological ionization drivers. 5. Develop algorithms to assimilate NASA satellite data of solar, interplanetary, and auroral observations into ionization source modules. 6. Use PENEX HF-link & HF-beacon data for skill score comparison of assimilation versus climatological D-region/HF absorption model. Only some satellites are available for the PENEX time period, thus, HF-beacon data is necessary. 7. Use HF beacon monitors to develop HF-link data assimilation algorithms for regional improvement to the D-region/HF absorption model.

Evidence of prompt penetration electric fields during HILDCAA events

NASA Astrophysics Data System (ADS)

Pereira Silva, Regia; Sobral, Jose Humberto Andrade; Koga, Daiki; Rodrigues Souza, Jonas

2017-10-01

High-intensity, long-duration continuous auroral electrojet (AE) activity (HILDCAA) events may occur during a long-lasting recovery phase of a geomagnetic storm. They are a special kind of geomagnetic activity, different from magnetic storms or substorms. Ionized particles are pumped into the auroral region by the action of Alfvén waves, increasing the auroral current system. The Dst index, however, does not present a significant downward swing as it occurs during geomagnetic storms. During the HILDCAA occurrence, the AE index presents an intense and continuous activity. In this paper, the response of Brazilian equatorial ionosphere is studied during three HILDCAA events that occurred in the year of 2006 (the descending phase of solar cycle 23) using the digisonde data located at São Luís, Brazil (2.33° S, 44.2° W; dip latitude 1.75° S). Geomagnetic indices and interplanetary parameters were used to calculate a cross-correlation coefficient between the Ey component of the interplanetary electric field and the F2 electron density peak height variations during two situations: the first of them for two sets daytime and nighttime ranges, and the second one for the time around the pre-reversal enhancement (PRE) peak. The results showed that the pumping action of particle precipitation into the auroral zone has moderately modified the equatorial F2 peak height. However, F2 peak height seems to be more sensitive to HILDCAA effects during PRE time, showing the highest variations and sinusoidal oscillations in the cross-correlation indices.

Comet Shoemaker-Levy-9 impact with Jupiter: Aeronomical predictions

NASA Technical Reports Server (NTRS)

Cravens, T. E.

1994-01-01

The fragments of comet Shoemaker-Levy-9 will enter the atmosphere of Jupiter during July 20-26, 1994. Significant amounts of water vapor will be injected into the upper atmosphere of Jupiter either from the comet itself or from the lower atmosphere of Jupiter. The photochemistry of both the neutral gas and the ionosphere will be greatly altered by the influx of this water vapor or the atomic oxygen generated by the dissociation of the water. Enhanced abundances of H2O (or other species such as NH3) in the atmosphere above the homopause should persist for at least a year and should be globally distributed. The odd oxygen (i.e., O or H2O or OH) associated with the cometary water influx alters the ion chemistry by removing H(+) ions, which also has the effect of reducing the ionospheric electron density because H(+) is ordinarily the main ion species in the Jovian ionosphere. The density of H3(+), both in the auroral and non-auroral ionosphere, will also be reduced due to presence of water. This ion species has been detected spectroscopically at Jupiter, and a drop in its abundance should be detectable. The major ion species will become H3O(+) which could reach a peak density as high as 10(exp 4)/cu cm in the non-auroral ionosphere and 10(exp 5)/cu cm in the auroral ionosphere. It should be possible to detect this ion species spectroscopically from Earth-based observatories.

Extreme Spacecraft Charging in Polar Low Earth Orbit

NASA Technical Reports Server (NTRS)

Colson, Andrew D.; Minow, Joseph I.; NeergaardParker, Linda

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 episodically charge to frame potentials in the kilovolt range when exposed to space weather environments characterized by a high flux of energetic (10 s kilovolt) electrons in regions of 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. We first review the physics of space environment 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. Finally, a set of extreme DMSP charging events are described varying in maximum negative frame potential from 0.6 kV to 2 kV, focusing on the characteristics of the charging events that are of importance both to the space system designer and to spacecraft operators. The goal of the presentation is to bridge the gap between scientific studies of auroral charging and the need for engineering teams to understand how space weather impacts both spacecraft design and operations for vehicles on orbital trajectories that traverse auroral charging environments.

Two types of energy-dispersed ion structures at the plasma sheet boundary

NASA Astrophysics Data System (ADS)

Sauvaud, J.-A.; Kovrazhkin, R. A.

2004-12-01

We study two main types of ion energy dispersions observed in the energy range ˜1 to 14 keV on board the Interball-Auroral (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 keV. 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 keV. In association with TDIS, bouncing H+ clusters are observed in quasi-dipolar magnetic field tubes, i.e., equatorward from TDIS. The electron populations generally have different properties during observations of VDIS and TDIS. The electron flux accompanying VDIS first increases smoothly and then decreases after Interball-Auroral has passed through the proton structure. The average electron energy in the range ˜0.5-2 keV is typical for electrons from the plasma sheet boundary layer (PSBL). The electron fluxes associated with TDIS increases suddenly at the polar boundary of the auroral zone. Their average energy, reaching ˜5-8 keV, is typical for CPS. A statistical analysis shows that VDIS are observed mainly during magnetically quiet times and during the recovery phase of substorms, while sporadic and recurrent TDIS are observed during the onset and main phases of substorms and magnetic storms and, although less frequently, during substorm recovery phases. From the slope of the (velocity)-1 versus time dispersions of TDIS, we conclude that they have a sporadic source located at the outer boundary of the central plasma sheet, at distances from 8 to 40 RE in the equatorial plane. The disappearance of the PSBL associated with TDIS can be tentatively linked to a reconfiguration of the magnetotail, which disconnects from the Earth the field lines forming the "quiet" PSBL. We show that VDIS consist of ion beams ejected from an extended current sheet at different distances. These ion beams could be formed in the neutral sheet at distance ranging from ˜30 RE to ˜100 RE from the Earth. Inside each substructure the time-of-flight dispersion of ions generally dominate over any latitudinal dispersion induced by a dawn-dusk electric field. These two main types of energy-dispersed ion structures reflect probably two main states of the magnetotail, quiet and active. Finally, it must be stressed that only ˜49% (246 over 501) of the Interball-Auroral auroral zone-polar cap boundary crossings can be described as VDIS or TDIS. On the other 51% of the crossings of the plasma sheet boundary, no well-defined ion dispersed structures were observed.

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.

A comparative study of auroral morphology distribution between the Northern and Southern Hemisphere based on automatic classification

NASA Astrophysics Data System (ADS)

Yang, Qiuju; Hu, Ze-Jun

2018-03-01

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 auroral morphology between the two hemispheres. Based on the morphological characteristics of the four labeled dayside discrete auroral types (auroral arc, drapery corona, radial corona and hot-spot aurora) on the 8001 dayside auroral 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 auroral images of the Chinese Arctic Yellow River Station during 2004-2009 and the 39 335 auroral images of the South Pole Station between 2003 and 2005. Finally, it obtains the occurrence distribution of the dayside auroral morphology in the Northern and Southern Hemisphere. The statistical results indicate that the four dayside discrete auroral 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 auroral morphology distribution between the Northern and Southern Hemisphere.

OVATION Prime -2013: Solar Wind Driven Precipitation Model Extended to Higher Geomagnetic Activity Levels (Invited)

NASA Astrophysics Data System (ADS)

Newell, P. T.; Liou, K.; Zhang, Y.; Paxton, L.; Sotirelis, T.; Mitchell, E. J.

2013-12-01

OVATION Prime is an auroral precipitation model parameterized by solar wind driving. Distinguishing features of the model include an optimized solar wind-magnetosphere coupling function (dΦMP/dt) which predicts auroral power far better than Kp or other traditional parameters, the separation of aurora into categories (diffuse aurora, monoenergetic, broadband, and ion), the inclusion of seasonal variations, and separate parameter fits for each MLATxMLT bin, thus permitting each type of aurora and each location to have differing responses to season and solar wind input (as indeed they do). We here introduce OVATION Prime-2013, an upgrade to the 2008 version currently widely available. The most notable advantage of OP-2013 is that it uses UV images from the GUVI instrument on the satellite TIMED for high disturbance levels (dΦMP/dt > 12,000 (nT2/3 (km/s)4/3 which roughly corresponds to Kp = 5+ or 6-). The range of validity is thought to be about 0 < dΦMP/dt = 30000 (say Kp = 8 or 8+). Other upgrades include a reduced susceptibility to salt and pepper noise, and smoother interpolation across the postmidnight data gap. We will also provide a comparison of the advantages and disadvantages of other current precipitation models, especially OVATION-SuperMAG, which produces particularly good estimates for total auroral power, at the expense of working best on an historical basis. OVATION Prime-2013, for high solar wind driving, as TIMED GUVI data takes over from DMSP

Records of auroral candidates and sunspots in Rikkokushi, chronicles of ancient Japan from early 7th century to 887

NASA Astrophysics Data System (ADS)

Hayakawa, Hisashi; Iwahashi, Kiyomi; Tamazawa, Harufumi; Ebihara, Yusuke; Kawamura, Akito Davis; Isobe, Hiroaki; Namiki, Katsuko; Shibata, Kazunari

2017-12-01

We present the results of the surveys on sunspots and auroral candidates in Rikkokushi, Japanese official histories from the early 7th century to 887, to review the solar and auroral activities. In total, we found one sunspot record and 13 auroral candidates in Rikkokushi. We then examine the records of the sunspots and auroral candidates, compare the auroral candidates with the lunar phase to estimate their reliability, and compare the records of the sunspots and auroral 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 auroral oval. These discussions suggest a major gap in auroral 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.

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 of 10 mW/m2 of 2 MeV/u oxygen ions, and a color ratio of 10 is expected for this case. Moreover, recent Juno data indicates the presence of both upward and downward relativistic energy beams over the polar cap, hence we perform some preliminary calculations of the effect of proton precipitation into the polar atmosphere and its contributions to the aurora dynamics.

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.

Generation and Similarity of the Jovian Satellite Footprints

NASA Astrophysics Data System (ADS)

Bonfond, B.

2017-12-01

A long chain of processes connects the satellite auroral footprints to the moon-magnetosphere interaction from which they originate. These processes include Alfvén waves' generation, filamentation, reflection, and bi-directional electron acceleration. The Io footprint is the most studied auroral footprint, because it is both the brightest one and the most isolated from other auroral emissions. It is made of at least three separate spots and an extended tail in the downstream direction. Early detections of the Europa and Ganymede footprints only identified single spots for these footprints, but re-analysis of the large dataset of Hubble Space Telescope images of the Jovian aurorae showed that they can also be made of multiple spots and display a tail. Moreover, the relative motion of these spots as a function of the location of the satellite is consistent with previous observations of the Io footprint, indicating that this dynamics corresponds to universal processes. Furthermore, a number of recent studies focused on the evolution of the brightness of these spots, with timescales ranging from minutes to days, and the signification of these changes will be reviewed. Finally, a discussion of the theoretical models explaining the footprint tails and their properties will be provided.

An Undergraduate Student Instrumentation Project (USIP) to Develop New Instrument Technology to Study the Auroral Ionosphere and Stratospheric Ozone Layer Using Ultralight Balloon Payloads

NASA Astrophysics Data System (ADS)

Gamblin, R.; Marrero, E.; Bering, E. A., III; Leffer, B.; Dunbar, B.; Ahmad, H.; Canales, D.; Bias, C.; Cao, J.; Pina, M.; Ehteshami, A.; Hermosillo, D.; Siddiqui, A.; Guala, D.

2014-12-01

This project is currently engaging tweleve undergraduate students in the process of developing new technology and instrumentation for use in balloon borne geospace investigations in the auroral zone. Motivation stems from advances in microelectronics and consumer electronic technology. Given the technological inovations over the past 20 years it now possible to develop new instrumentation to study the auroral ionosphere and stratospheric ozone layer using ultralight balloon payloads for less than 6lbs and $3K per payload. The UH USIP undergraduate team is currently in the process of build ten such payloads for launch using1500 gm latex weather balloons to be deployed in Houston and Fairbanks, AK as well as zero pressure balloons launched from northern Sweden. The latex balloon project will collect vertical profiles of wind speed, wind direction, temperature, electrical conductivity, ozone and odd nitrogen. This instrument payload will also profiles of pressure, electric field, and air-earth electric current. The zero pressure balloons will obtain a suite of geophysical measurements including: DC electric field, electric field and magnetic flux, optical imaging, total electron content of ionosphere via dual-channel GPS, X-ray detection, and infrared/UV spectroscopy. Students will fly payloads with different combinations of these instruments to determine which packages are successful. Data collected by these instruments will be useful in understanding the nature of electrodynamic coupling in the upper atmosphere and how the global earth system is changing. Results and best practices learned from lab tests and initial Houston test flights will be discussed.

Updated modeling of Io and non-Io Radio Auroral Emissions of Jupiter

NASA Astrophysics Data System (ADS)

Louis, C.; Lamy, L.; Zarka, P.; Cecconi, B.; Hess, S.

2015-10-01

The radio auroral 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 auroral radio emissions are thought to be produced through the Cyclotron Maser Instability (CMI), from non-maxwellian weakly relativistic electrons 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 electrons (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).

Low-altitude acceleration of auroral electrons during breakup observed by a mother-daughter rocket

NASA Technical Reports Server (NTRS)

Johnstone, A. D.; Davis, T. N.

1974-01-01

By the use of a mother-daughter rocket combination and ground-based observations with television, time and space variations are resolved in particle measurements in breakup aurora. The spectral variations measured during a temporal variation in the aurora can be explained by a nearly uniform acceleration of all the electrons such as would be caused by an electric potential drop along the magnetic field lines. Many other explanations can be eliminated.

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.

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.

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.

Ionospheric electron number densities from CUTLASS dual-frequency velocity measurements using artificial backscatter over EISCAT

NASA Astrophysics Data System (ADS)

Sarno-Smith, Lois K.; Kosch, Michael J.; Yeoman, Timothy; Rietveld, Michael; Nel, Amore'; Liemohn, Michael W.

2016-08-01

Using quasi-simultaneous line-of-sight velocity measurements at multiple frequencies from the Hankasalmi Cooperative UK Twin Auroral Sounding System (CUTLASS) on the Super Dual Auroral Radar Network (SuperDARN), we calculate electron number densities using a derivation outlined in Gillies et al. (2010, 2012). Backscatter targets were generated using the European Incoherent Scatter (EISCAT) ionospheric modification facility at Tromsø, Norway. We use two methods on two case studies. The first approach is to use the dual-frequency capability on CUTLASS and compare line-of-sight velocities between frequencies with a MHz or greater difference. The other method used the kHz frequency shifts automatically made by the SuperDARN radar during routine operations. Using ray tracing to obtain the approximate altitude of the backscatter, we demonstrate that for both methods, SuperDARN significantly overestimates Ne compared to those obtained from the EISCAT incoherent scatter radar over the same time period. The discrepancy between the Ne measurements of both radars may be largely due to SuperDARN sensitivity to backscatter produced by localized density irregularities which obscure the background levels.

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.

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.

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 waves would experience due to Landau damping on the topside ionosphere and mode conversion on the bottomside ionosphere. The amount of Landau damping is sensitive to the ratio of secondary to background electrons nse/ne0. Ignoring collisional damping in the lower ionosphere, these calculations suggest that for nse/n e0<0.4%, 0.01-45% of the initial Langmuir wave power would reach ground-level. The above experimental and numerical studies constrain the conditions under which MF burst could plausibly originate as Langmuir/Z-mode waves on the topside of the ionosphere.

Relative Timing of Substorm-Associated Processes in the Near-Earth Magnetotail and Development of Auroral Onset Arc

NASA Astrophysics Data System (ADS)

Miyashita, Y.; Ieda, A.; Machida, S.; Hiraki, Y.; Angelopoulos, V.; McFadden, J. P.; Auster, H. U.; Mende, S. B.; Donovan, E.; Larson, D. E.

2014-12-01

We have studied the relative timing of the processes in the near-Earth magnetotail and development of auroral 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 auroral development in more detail than before. A few min after the appearance and intensification of an auroral onset arc, it begins to form wave-like structure. Then auroral 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 auroral 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 auroral wave-like structure. Dipolarization begins at the same time as the auroral poleward expansion. These results suggest that near-Earth magnetic reconnection plays some role in the development of dipolarization and auroral onset arc.

Jupiter's auroral-related stratospheric heating and chemistry II: Analysis of IRTF-TEXES spectra measured in December 2014

NASA Astrophysics Data System (ADS)

Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Moses, J. I.; Hue, V.; Irwin, P. G. J.

2018-01-01

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 auroral processes modify the thermal structure and hydrocarbon chemistry of the stratosphere. In qualitative agreement with Sinclair et al. (2017a), we find temperatures in auroral 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 auroral 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 electron and ion precipitation. However, temperatures at 1 mbar are considered to result either from heating by shortwave radiation of aurorally-produced haze particulates or precipitation of higher energy population of charged particles. Our former conclusion would be consistent with results of auroral-chemistry models, that predict the highest number densities of aurorally-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 auroral 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°W and at 0.01 mbar, over the same longitude range at 70°N, C2H4 increases from 0.669 ± 0.129 ppmv to 6.509 ± 0.811 ppmv. However, we note that non-LTE (local thermodynamic equilibrium) emission may affect the cores of the strongest C2H2 and C2H4 lines on the northern auroral region, which may be a possible source of error in our derived concentrations. We retrieved concentrations of C2H6 at 1 mbar of 9.03 ± 0.98 ppmv at 70°N, 60°W and 7.66 ± 0.70 ppmv at 70°N, 180°W. Thus, C2H6's concentration appears constant (within uncertainty) as a function of longitude at 70°N.

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.

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 with the quiet-background in temperature, both in magnitude and climatology.

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 constrained simulations are compared against in-situ observations. This allows for the ionospheric temperature anisotropies, which are notoriously difficult to observe, and their impacts on ion upflow response due to auroral drivers to be evaluated by enforcing realistic temporal and spatial dependencies on the drivers.

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.

UV Observations of Hemispheric Asymmetry

NASA Astrophysics Data System (ADS)

Schaefer, R. K.; Paxton, L. J.; Wolven, B. C.; Zhang, Y.; Romeo, G.

2015-12-01

Asymmetry in the auroral patterns can be an important diagnostic for understanding the dynamics of solar wind interaction with the magnetosphere-ionosphere-thermosphere system (e.g., Newel and Meng, 1998; Fillingrim et al., 2005). Molecular nitrogen emission in the UV Lyman-Birge-Hopfield bands can be used to determine energy flux and electron mean energy (Sotirelis, et al, 2013) and thereby Hall and Pederson integrated conductances (Gjerloev, et al., 2014). UV imagery provided by the 4 SSUSI instruments on the Defense Meteorological Satellite Program (DMSP) F16-F19 spacecraft provide two dimensional maps of this emission at different local times. Often there are near simultaneous observations of both poles by some combination of the satellites. (see figure 1) The SSUSI auroral data products are well suited to this study, as they have the following features.: - dayglow has been subtracted on dayside aurora - electron energy flux and mean energy are pre-calculated - individual arcs have been identified through image processing. In order to intercompare data from multiple satellites, we must first ensure that the instrument calibrations are consistent. In this work we show that the instruments are consistently calibrated, and that results generated from the SSUSI data products can be trusted. Several examples of storm time asymmetries captured by the SSUSI instruments will be discussed. Fillingim, M. O., G. K. Parks, H. U. Frey, T. J. Immel, and S. B. Mende (2005), Hemispheric asymmetry of the afternoon electron aurora, Geophys. Res. Lett., 32, L03113, doi:10.1029/2004GL021635. Gjerloev, J., Schaefer, R., Paxton, L, and Zhang, Y. (2014), A comprehensive empirical model of the ionospheric conductivity derived from SSUSI/GUVI, SuperMAG and SuperDARN data, SM51G-4339, Fall 2014 AGU meeting, San Francisco. Newell, P. T., and C.-I. Meng (1988), Hemispherical asymmetry in cusp precipitation near solstices, J. Geophys. Res., 93(A4), 2643-2648, doi:10.1029/JA093iA04p02643. Sotirelis, T., Korth, H., Hsieh, S. - Y., Zhang, Y., Morrison, D., and Paxton, L., (2013), "Empirical relationship between electron precipitation and far-ultraviolet auroral emissions from DMSP observations", Journal of Geophysical Research: Space Physics, vol. 118, no. 3, pp. 1203 - 1209.

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.

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.

Cyclotron maser instability and its applications

NASA Astrophysics Data System (ADS)

Wu, C. S.

The possible application of cyclotron maser theory to a variety of radio sources is considered, with special attention given to the theory of auroral kilometric radiation (AKR) of Wu and Lee (1979). The AKR model assumes a loss-cone distribution function for the reflected electrons, along with the depletion of low-energy electrons by the parallel electric field. Other topics considered include fundamental AKR, second-harmonic AKR, the generation of Z-mode radiation, and the application of maser instability to other sources than AKR.

Media Effects on Electronic Systems in the High Latitude Region

DTIC Science & Technology

1988-09-01

oval and auroral electron densities. Essentially the ICED model is still based on a set of coefficients, but these are modified by other inputs. There...and larger. At the distance of the Earth’s orbit the speed of the solar wind is usually between 200 and 700 or 800 km s -1 , on which is superimposed a...magnetometer on IMP-I (the Interplanetary Monitoring Platform), an eccentric orbit satellite with apogee at 32 RE Although the solar wind flows out almost

Initial observations of Jupiter's aurora from Juno's Ultraviolet Spectrograph (Juno-UVS)

NASA Astrophysics Data System (ADS)

Gladstone, R.; Versteeg, M.; Greathouse, T.; Hue, V.; Davis, M. W.; Gerard, J. C. M. C.; Grodent, D. C.; Bonfond, B.; Bolton, S. J.; Connerney, J. E. P.; Levin, S.; Bagenal, F.; Mauk, B.; Kurth, W. S.; McComas, D. J.; Valek, P. W.

2016-12-01

Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes important far-ultraviolet (FUV) emissions from the H2 bands and the H Lyman series which are produced in Jupiter's auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4x4 cm2 input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a "dog-bone" shape, with three sections of 2.55°x0.2°, 2.0°x0.025°, and 2.55°x0.2° (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses FUV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. The two mirrors and the grating are coated with MgF2 to improve FUV reflectivity. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno's spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter's auroral morphology and brightness to provide context for in situ measurements by Juno's particle instruments. Here we present the first near-Jupiter results from the UVS instrument following measurements made during PJ1, Juno's first perijove pass with its instruments powered on and taking data.

Plasma Interactions with Spacecraft. Volume 2, NASCAP-2K Scientific Documentation for Version 4.1

DTIC Science & Technology

2011-04-15

E expn E m2 e EF (2) Double Maxwellian                      2 2 221 1 11 E expn E m2 eE expn E...m2 e EF (3) Fontheim (electrons only) This distribution is used to model auroral electrons.      LUpower 2 gauss o gaussmax EEHEEHE EE ...to secondary electron current. ee emitted secondary current due to electron impact Y primary electron current  (16) A typical curve is shown in

Cusp/cleft auroral activity in relation to solar wind dynamic pressure, interplanetary magnetic field B(sub z) and B(sub y)

NASA Technical Reports Server (NTRS)

Sandholt, P. E.; Farrugia, C. J.; Burlaga, L. F.; Holtet, J. A.; Moen, J.; Lybekk, B.; Jacobsen, B.; Opsvik, D.; Egeland, A.; Lepping, R.

1994-01-01

Continuous optical observations of cusp/cleft auroral 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 auroral transients, and distinct ground magnetic signatures of enhanced convection at cleft latitudes. A sequence of auroral 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 auroral 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 auroral event sequence is stimulated bursts of electron precipitation that originate from magnetosheath plasma that has accessed that dayside magnetosphere in the noon or near-noon sector, possibly at high latitudes, partly governed by the IMF orientation as well as by solar wind dynamic pressure pulses.

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