Plasmapause Variations During the 17 March 2013 Identified by Ground-based and Space-based GPS Signals

NASA Astrophysics Data System (ADS)

Bishop, R. L.; Coster, A. J.; Turner, D. L.; Nikoukar, R.; Lemon, C.; Bust, G. S.; Roeder, J. L.

2016-12-01

Earth's plasmasphere is a region of cold (T ≤ 1 eV), dense (n 101 to 104 cm-3) plasma located in the inner magnetosphere and coincident with a portion of the ionosphere that co-rotates with the planet in the geomagnetic field. Plasmaspheric plasma originates in the ionosphere and fills the magnetic flux tubes on which the corotation electric field dominates over the convection electric field. The corotation electric field results from Earth's spinning magnetic field while the convection electric field results from the solar wind driving of global plasma convection within the magnetosphere. The outer boundary of the plasmasphere is the plasmapause, and it corresponds to the transition region between corotation-driven vs. convection-driven plasmas. During quiet periods of low solar wind speed and weak interplanetary magnetic field (IMF), ionospheric outflow from lower altitudes can fill the plasmasphere over the course of several days with the plasmapause expanding to higher L-shells. However, when the convection electric field is enhanced during active solar wind periods, such as magnetic storms, the plasmasphere can be rapidly eroded to L 2.5 or less leading to many interesting magnetospheric and ionospheric features such as plasmapause erosion, plasmaspheric plumes and ionospheric plasma outflows. In this presentation, we focus on the dynamics of the plasmapause as observed by ground-based and space-borne GPS receivers. We will focus on the period 15 March to 19 March 2013, which includes the on-set and recovery periods of a strong geomagnetic storm. We will examine the location and erosion time scales of the plasmapause during the active portion of the storm. An extensive global network of ground-based scientific receivers ( 4000) will be utilized in the study. Space-based observations will be obtained from data from the CORISS GPS radio occultation (RO) sensor on the C/NOFS satellite as well as the COSMIC GPS RO sensors.

Modeling the Impenetrable Barrier to Inward Transport of Ultra-relativistic Radiation Belt Electrons

NASA Astrophysics Data System (ADS)

Tu, W.; Cunningham, G.; Chen, Y.; Baker, D. N.; Henderson, M. G.; Reeves, G. D.

2014-12-01

It has long been considered that the inner edge of the Earth's outer radiation belt is closely correlated with the minimum plasmapause location. However, recent discoveries by Baker et al. [1] show that it is not the case for ultra-relativistic electrons (2-10 MeV) in the radiation belt. Based on almost two years of Van Allen Probes/REPT data, they find that the inner edge of highly relativistic electrons is rarely collocated with the plasmapause; and more interestingly, there is a clear, persistent, and nearly impenetrable barrier to inward transport of high energy electrons, observed to locate at L~2.8. The presence of such an impenetrable barrier at this very specific location poses a significant puzzle. Using our DREAM3D diffusion model, which includes radial, pitch angle, and momentum diffusion, we are able to simulate the observed impenetrable barrier of ultra-relativistic electrons. The simulation demonstrates that during strong geomagnetic storms the plasmapause can be compressed to very low L region (sometimes as low as L~3), then strong chorus waves just outside the plasmapause can locally accelerate electrons up to multiple-MeV; when storm recovers, plasmapause moves back to large L, while the highly-relativistic electrons generated at low L continue to diffuse inward and slow decay by pitch angle diffusion from plasmaspheric hiss. The delicate balance between slow inward radial diffusion and weak pitch angle scattering creates a fixed inner boundary or barrier for ultra-relativistic electrons. The barrier is found to locate at a fixed L location, independent of the initial penetration depth of electrons that is correlated with the plasmapause location. Our simulation results quantitatively reproduce the evolution of the flux versus L profile, the L location of the barrier, and the decay rate of highly energetic electrons right outside the barrier. 1Baker, D. N., et al. (2014), Nearly Impenetrable Barrier to Inward Ultra-relativistic Magnetospheric Electron Transport, submitted to Nature.

Micropulsations in the electric field near the plasmapause, observed by ISEE-1

NASA Technical Reports Server (NTRS)

Moe, T. E.; Maynard, N. C.; Heppner, J. P.

1979-01-01

The occurrence of micropulsations near and inside the plasmapause was surveyed. The observed pulsations, classified as Pc3 and Pi2, are discussed. In addition one single event of Pc1 was observed. The frequencies in the Pc3 and Pi2 bands, the amplitude ranges, and the direction of rotation for the electric field vector are reported.

Thermal ion heating in the vicinity of the plasmapause: A Dynamics Explorer guest investigation

NASA Technical Reports Server (NTRS)

Comfort, R. H.

1986-01-01

The ion thermal structure of the plasmasphere was investigated in a series of experiments. It appears that energy may be generally available to ion and electrons in the vinicity of the plasmapause from Coulomb interactions between ambient thermal plasma and low energy ring current and suprathermal ions, particularly O+. The amount of energy transferred depends on the densities and energies of each of the components. The spatial distribution of heating in turn depends critically on the spatial distribution of the different populations, especially on the density gradients. The spatial distribution of the thermal plasma is found to vary significantly on a diurnal time scale and is complicated by the plasmasphere erosion and refilling processes associated with magnetic activity and its aftermath. Thermal ion composition also appears to be influenced by the heating taking place, often increasing the heavy ion population in the vicinity of the plasmapause. The observations of equatorial heating near the plasmapause in the presence of equatorial noise also raise the likelihood of a wave source of energy. It is not unreasonable to expect that both particle and wave heat sources are significant, although not necessarily at the same times and places.

VLF emissions and whistlers observed during geomagnetic storms

NASA Technical Reports Server (NTRS)

Ondoh, T.; Tanaka, Y.; Nishizaki, R.; Nagayama, M.

1974-01-01

Whistler-triggered emissions and a narrowband hiss are described which were observed over Japan by ISIS 2 during the main phase of the geomagnetic storm of August 9, 1972. The characteristics of the narrowband hiss and increases in the whistler rate during the storm are discussed, and the ISIS-2 data are compared with data on whistler cutoffs and VLF noise breakups obtained by OGO 4 and Alouette I. Since the whistlers and narrowband hiss are usually observed inside and outside the plasmapause, it is thought that the plasmapause may have been located near the low-latitude end of the narrowband hiss during the main phase of the storm. It is suggested that the increases in the whistler rate may have been caused by the formation of whistler ducts in the disturbed plasmapause.

Plasmapause Dynamics Observed During the 17 March and 28 June 2013 Storms

NASA Astrophysics Data System (ADS)

Bishop, R. L.; Coster, A. J.; Turner, D. L.; Nikoukar, R.; Lemon, C.; Roeder, J. L.; Shumko, M.; Bhatt, R.; Payne, C.; Bust, G. S.

2017-12-01

Earth's plasmasphere is a region of cold (T ≤ 1 eV), dense (n 101 to 104 cm-3) plasma located in the inner magnetosphere and coincident with a portion of the ionosphere that co-rotates with the planet in the geomagnetic field. Plasmaspheric plasma originates in the ionosphere and fills the magnetic flux tubes on which the corotation electric field dominates over the convection electric field. The corotation electric field results from Earth's spinning magnetic field while the convection electric field results from the solar wind driving of global plasma convection within the magnetosphere. The outer boundary of the plasmasphere is the plasmapause, and it corresponds to the transition region between corotation-driven vs. convection-driven plasmas. When the convection electric field is enhanced during active solar wind periods, such as magnetic storms, the plasmasphere can rapidly erode to L 2.5 or less. During subsequent quiet periods of low solar wind speed and weak interplanetary magnetic field (IMF), ionospheric outflow from lower altitudes refills the plasmasphere over the course of several days or more, with the plasmapause expanding to higher L-shells. The combination of convection, corotation, and ionospheric plasma outflow during and after a storm leads to characteristic features such as plasmaspheric shoulders, notches, and plumes. In this presentation, we focus on the dynamics of the plasmapause during two storms in 2013: March 17 and June 28. The minimum Dst for the two storms were -139 and -98 nT, respectively. We examine plasmapause dynamics utilizing data from an extensive global network of ground-based scientific GPS receivers ( 4000) and line-of-sight observations from the GPS receivers on the COSMIC and C/NOFS satellites, along with data from THEMIS and van Allen Probes, and Millstone Hill Incoherent Scatter Radar. Using the various datasets, we will compare the pre-storm and storm-time plasmasphere. We will also examine the location, evolution, and erosion time scales of the plasmapause during the active portion of the storm using a combination of the observational data, the assimilative PDA model, and the RCM-E model.

A monopole model for annihilation line emission from the Galactic center

NASA Astrophysics Data System (ADS)

Wang, D. Y.; Peng, Q. H.

Two traditional theoretical interpretations of the observed plasmapause are compared, namely, the plasmapause as: (1) the boundary between closed flux tubes that have been in the inner magnetosphere for several days and those that have recently drifted in from the magnetotail or (2) the last closed electric equipotential. Although the two interpretations become equivalent in the case where the electric-field pattern is steady for several days, interpretation 1 seems theoretically more secure for typical magnetospheric conditions. The results of old theoretical studies of the effects of time variations in the electric-field pattern on the shape of the plasmapause are reviewed briefly. The formulation of the present version of the Rice Convection Model is also reviewed. Preliminary results of recent computations of quiet-time electric fields, carried out with this model, are presented and discussed.

Whistlers observed outside the plasmasphere: Correlation to plasmaspheric/plasmapause features

NASA Astrophysics Data System (ADS)

Adrian, M. L.; Fung, S. F.; Gallagher, D. L.; Green, J. L.

2015-09-01

Whistlers observed outside the plasmasphere by Cluster have been correlated with the global plasmasphere using Imager for Magnetopause-to-Aurora Global Exploration-Extreme Ultraviolet Imager (IMAGE-EUV) observations. Of the 12 Cluster-observed whistler events reported, EUV is able to provide global imaging of the plasmasphere for every event and demonstrates a direct correlation between the detection of lightning-generated whistlers beyond the plasmapause and the presence of a global perturbation of the local plasmapause. Of these 12 correlated events, seven of the Cluster-observed whistlers (or 58%) are associated with the Cluster spacecraft lying radially outward from a plasmaspheric notch. Two of the Cluster-observed whistlers (17%) are associated with the low-density region between the late afternoon plasmapause and the western wall of a plasmaspheric drainage plume. The final three Cluster-observed whistler events (25%) are associated with a nonradial, nonazimuthal depletion in plasmaspheric He+ emission that are termed "notch-like" crenulations. In one of these cases, the notch-like crenulations appear to be manifestations entrained within the plasmasphere boundary layer of a standing wave on the surface of the plasmasphere. The correlated Cluster/IMAGE-EUV observations suggest that the depleted flux tubes that connect the ionosphere to the low-density regions of plasmaspheric trough and inner magnetosphere facilitate the escape of whistler waves from the plasmasphere.

Ogo 5 observations of LHR noise, emissions, and whistlers near the plasmapause at several earth radii during a large magnetic storm.

NASA Technical Reports Server (NTRS)

Scarf, F. L.; Fredricks, R. W.; Smith, E. J.; Frandsen, A. M. A.; Serbu, G. P.

1972-01-01

On May 15, 1969, Ogo 5 crossed the plasmapause during a major storm that produced severe geomagnetic disturbances (Kp up to 8-), large and rapid variations in ring-current intensity (as measured by Dst), intense low-latitude aurora, and persistent SAR arcs. Near the highly structured plasmasphere boundary, the electric- and magnetic-field sensors on Ogo 5 detected lower-hybrid-resonance noise bursts, whistlers, ELF hiss, and other discrete signals or emissions. Some LHR noise bursts were associated with whistlers, and these high-altitude phenomena resembled the corresponding ionospheric ones. This report contains a description of the VLF observations. We also show that intense ULF magnetic signals were present near the plasmapause, and we attempt to relate these observations to the predictions of various theories of proton ring-current decay and SAR-arc formation.

Comparison of H+ and He+ Plasmapause Locations Based on Resurrected and Reevaluated OGO-5 Ion Composition Data Base

NASA Technical Reports Server (NTRS)

Truhlik, Vladimir; Triskova, Ludmila; Benson, Robert F.; Bilitza, Dieter; Grebowsky, Joseph; Richards, Phil G.; Smilauer, Jan

2014-01-01

Orbiting Geophysical Observatory 5 (OGO 5) magnetospheric ion-composition data (H+, He+ and O+) from an ion spectrometer (Sharp, 1969) have been retrieved from old magnetic tapes archived at the National Space Science Data Center (NSSDC). The highly compressed binary format was converted into a user-friendly ASCII format and these data have been made available online. We have inspected reliability and consistency of this data set in state of the art current knowledge. Comparing with the climatological model IRI-2012 and the mathematical model FLIP a shift of absolute and relative ion densities with time was revealed. We have suggested a correction procedure of individual H+, He+ and O+ ion densities. Using the corrected data set, we investigated plasmapause locations based on density gradient in H+, and He+. Correlation coefficient of both locations was determined as approx. 0.886 and the typical difference (Delta)L approx. 0.1. The electron density at the He+ plasmapause location for all cases is >100/cu cm.

Van Allen Probes Observations of the Plasmasphere and Radiation Belts

NASA Astrophysics Data System (ADS)

Goldstein, J.; Jahn, J. M.; De Pascuale, S.; Kletzing, C.; Kurth, W. S.; Genestreti, K. J.; Skoug, R. M.; Larsen, B.; Kistler, L. M.; Mouikis, C.; Spence, H. E.; Reeves, G. D.; Baker, D. N.; Blake, J. B.

2014-12-01

Van Allen Probes (RBSP) observations during 15-20 January 2013 are the basis of this study of the spatial relationship between the plasmasphere and radiation belts, and its influence on energy dependent lifetimes of energetic electrons. We use a convection-driven plasmapause test particle (PTP) simulation to provide contextual information for in situ measurements by RBSP during 15-20 January 2013, and find that the model reproduces the observed plasmapause radial locations to within 0.40 Earth radii (RE). We use analysis of the RBSP data to examine the radial structure of both the plasmasphere and radiation belts for the selected 5-day period, which includes a moderate geomagnetic disturbance on 17 January. RBSP observed three belts (inner, outer, and storage ring) prior to the 17 January disturbance, and two belts (inner and outer) afterward. The plasmapause aligns with the outermost belt. We examine the energy dependence of the radial structure and decay lifetimes of energetic electrons, both inside and outside the plasmasphere.

Effect of spatial density variation and O+ concentration on the growth and evolution of electromagnetic ion cyclotron waves

DOE PAGES

Denton, R. E.; Jordanova, V. K.; Fraser, B. J.

2014-10-01

We simulate electromagnetic ion cyclotron (EMIC) wave growth and evolution within three regions, the plasmasphere (or plasmaspheric plume), the plasmapause, and the low-density plasmatrough outside the plasmapause. First, we use a ring current simulation with a plasmasphere model to model the particle populations that give rise to the instability for conditions observed on 9 June 2001. Then, using two different models for the cold ion composition, we do a full scale hybrid code simulation in dipole coordinates of the EMIC waves on a meridional plane at MLT = 18 and at 1900 UT within a range of L shell frommore » L = 4.9 to 6.7. EMIC waves were observed during June 9, 2001 by Geostationary Operational Environmental Satellite (GOES) spacecraft. While an exact comparison between observed and simulated spectra is not possible here, we do find significant similarities between the two, at least at one location within the region of largest wave growth. We find that the plasmapause is not a preferred region for EMIC wave growth, though waves can grow in that region. The density gradient within the plasmapause does, however, affect the orientation of wave fronts and wave vector both within the plasmapause and in adjacent regions. There is a preference for EMIC waves to be driven in the He+ band (frequencies between the O+ and He+ gyrofrequencies) within the plasmasphere, although they can also grow in the plasmatrough. If present, H+ band waves are more likely to grow in the plasmatrough. This fact, plus L dependence of the frequency and possible time evolution toward lower frequency waves, can be explained by a simple model. Large O+ concentration limits the frequency range of or even totally quenches EMIC waves. This is more likely to occur in the plasmatrough at solar maximum. Such large O+ concentration significantly affects the H+ cutoff frequency and hence the width in frequency of the stop band above the He+ gyrofrequency. EMIC wave surfaces predicted by cold plasma theory are altered by the finite temperature of the ring current H+.« less

Effect of spatial density variation and O+ concentration on the growth and evolution of electromagnetic ion cyclotron waves

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

Denton, R. E.; Jordanova, V. K.; Fraser, B. J.

We simulate electromagnetic ion cyclotron (EMIC) wave growth and evolution within three regions, the plasmasphere (or plasmaspheric plume), the plasmapause, and the low-density plasmatrough outside the plasmapause. First, we use a ring current simulation with a plasmasphere model to model the particle populations that give rise to the instability for conditions observed on 9 June 2001. Then, using two different models for the cold ion composition, we do a full scale hybrid code simulation in dipole coordinates of the EMIC waves on a meridional plane at MLT = 18 and at 1900 UT within a range of L shell frommore » L = 4.9 to 6.7. EMIC waves were observed during June 9, 2001 by Geostationary Operational Environmental Satellite (GOES) spacecraft. While an exact comparison between observed and simulated spectra is not possible here, we do find significant similarities between the two, at least at one location within the region of largest wave growth. We find that the plasmapause is not a preferred region for EMIC wave growth, though waves can grow in that region. The density gradient within the plasmapause does, however, affect the orientation of wave fronts and wave vector both within the plasmapause and in adjacent regions. There is a preference for EMIC waves to be driven in the He+ band (frequencies between the O+ and He+ gyrofrequencies) within the plasmasphere, although they can also grow in the plasmatrough. If present, H+ band waves are more likely to grow in the plasmatrough. This fact, plus L dependence of the frequency and possible time evolution toward lower frequency waves, can be explained by a simple model. Large O+ concentration limits the frequency range of or even totally quenches EMIC waves. This is more likely to occur in the plasmatrough at solar maximum. Such large O+ concentration significantly affects the H+ cutoff frequency and hence the width in frequency of the stop band above the He+ gyrofrequency. EMIC wave surfaces predicted by cold plasma theory are altered by the finite temperature of the ring current H+.« less

Is the Linear Mode Conversion Theory Viable for Generating Kilometric Continuum?

NASA Technical Reports Server (NTRS)

Boardsen, Scott A.; Green, James L.; Hashimoto, K.; Gallagher, Dennis L.; Webb, P. A.

2006-01-01

Kilometric Continuum (KC) usually exhibits a complicated banded radiation pattern observed in frequency time spectrograms. Can the number of bands, the frequency range over which the bands are observed, and their time variation be explained with Linear Mode Conversion Theory (LMCT) using realistic plasmapause models and Extreme Ultraviolet (EUV) plasmaspheric observations? In this paper we compare KC observations with simulated frequency emission bands based on LMCT for a number of cases. In LMCT the allowed frequency range across the equatorial plasmapause is restricted to frequencies much greater than the electron cyclotron frequency (fce) and less than the maximum plasma frequency in this region. Fce also determines the number of allowed bands in this range. Is the observed frequency range and number of bands consistent with the predications of LMCT? Can irregularities in the shape of plasmaspheric structures like notches be observed in the time variations of KC emissions? We will investigate these and other questions. Simulated radiation patterns will be generated by ray tracing calculations in the L-O mode from the radio window at the near equatorial plasmapause. The KC observations used in this study are from the Plasma Wave Instrument on the Geotail spacecraft and from the Radio Plasma Imager on the IMAGE spacecraft. The plasmasphere and plasmapause will be derived either from plasmasphere simulations, from images by the EUV imager on the IMAGE spacecraft, and by using empirical models. In situ plasma density measurements from a number of spacecraft will also be used in order to reconstruct the plasmasphere for these case studies.

Cluster observations of EMIC triggered emissions in association with Pc1 waves near Earth's plasmapause

NASA Astrophysics Data System (ADS)

Pickett, J. S.; Grison, B.; Omura, Y.; Engebretson, M. J.; Dandouras, I.; Masson, A.; Adrian, M. L.; Santolík, O.; Décréau, P. M. E.; Cornilleau-Wehrlin, N.; Constantinescu, D.

2010-05-01

The Cluster spacecraft were favorably positioned on the nightside near the equatorial plasmapause of Earth at L ˜ 4.3 on 30 March 2002 to observe electromagnetic ion cyclotron (EMIC) rising tone emissions in association with Pc1 waves at 1.5 Hz. The EMIC rising tone emissions were found to be left-hand, circularly polarized, dispersive, and propagating away from the equator. Their burstiness and dispersion of ˜30s/Hz rising out of the 1.5 Hz Pc1 waves are consistent with their identification as EMIC triggered chorus emissions, the first to be reported through in situ observations near the plasmapause. Along with the expected H+ ring current ions seen at higher energies (>300 eV), lower energy ions (300 eV and less) were observed during the most intense EMIC triggered emission events. Nonlinear wave-particle interactions via cyclotron resonance between the ˜2-10 keV H+ ions with temperature anisotropy and the linearly-amplified Pc1 waves are suggested as a possible generation mechanism for the EMIC triggered emissions.

The plasmapause period of magnetic recovery. Combined study of OGO 4, OGO 5 data and of grounded whistler reception

NASA Technical Reports Server (NTRS)

Corcuff, P.; Corcuff, Y.; Carpenter, D. L.; Chappell, C. R.; Vigneron, J.; Kleimenova, N.

1972-01-01

The equatorial structure and dynamics of the plasmasphere during the period of magnetic recovery, lasting from the 13 to 23 of September 1968, are studied. The H(+) ions density profiles measured in the night and afternoon sectors by the excentered orbital satellite OGO 5 and L sub p positions of the plasmapause deduced from the VLF records of the polar orbital satellite OGO 4, are included. Electron densities are calculated from the whistlers received at Kerguelen (L approximately 3, 7) and Byrd (L approximately 7), ground stations 150 degrees of longitude apart.

Van Allen Probes Observations of Plasmasphere Refilling Inside and Outside the Plasmapause

NASA Astrophysics Data System (ADS)

De Pascuale, S.; Kletzing, C.; Kurth, W. S.; Jordanova, V. K.

2017-12-01

We survey several geomagnetic storms observed by the Van Allen Probes to determine the rate of plasmasphere refilling following the initial erosion of the plasmapause region. The EMFISIS instrument on board the spacecraft provides near-equatorial in situ electron density measurements, which are accurate to 10% error in the detectable range 2 < L < 6. Two-dimensional plasmasphere density simulations, providing global context of local observations, are driven by the incident solar wind electric field as a proxy for geomagnetic activity. The simulations utilize a semi-empirical model of convection and a semi-empirical model of ionospheric outflow to dynamically evolve plasmaspheric densities. We find that at high L the plasmasphere undergoes orders of magnitude density depletion (from 100s - 10s cm-3) in response to a geomagnetic event and recovers to pre-storm levels over many days. At low L ( 1000s cm-3), and within the plasmapause, the plasmasphere loses density by a factor of 2 to 3 (from 3000 - 1000 cm-3) producing a depletion that can persist over weeks during sustained geomagnetic activity. We describe the impact of these results on the challenge of defining a saturated quiet state of the plasmasphere.

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.

Extreme Magnetosphere-Ionosphere Coupling at the Plasmapause: a - In-A Bright SAR Arc

NASA Astrophysics Data System (ADS)

Baumgardner, J.; Wroten, J.; Semeter, J.; Mendillo, M.; Kozyra, J.

2007-05-01

Heat conduction from the ring current - plasmapause interaction region generates high electron temperature within the ionosphere that drive stable auroral red (SAR) arc emission at 6300 A. On the night of 29 October 1991, a SAR arc was observed using an all-sky imager and meridional imaging spectrograph at Millstone Hill. At xxxx UT, the SAR arc was south of Millstone at approximate L = 2 and reached emission levels of 13,000 rayleighs (R). Over two solar cycle of imaging observations have been made at Millstone Hill, and SAR arc brightness levels (excluding this event) averaged ~ 500 R. Simultaneous observations using the incoherent scatter radar (ISR), a DMSP satellite pass, the MSIS neutral atmosphere and SAR arc modeling using the Rees and Roble formalism succeeded in simulations of the observed emission. The reason for the unusual brightness was not the extreme temperatures achieved (and therefore heat conduction input), but the fact that the end of the plasmapause field line where the elevated Te values were measured did not occur in the ionospheric trough, but equatorward of it, thereby having far more ambient electrons to heat and subsequently collide with atomic oxygen. This unusual spatial geometry probably resulted from unusual convection patterns early in a superstorm scenario.

Equatorial measurement of SAID electric fields and relation with the plasmapause location

NASA Astrophysics Data System (ADS)

Nishimura, Y.; Wygant, J.; Ono, T.; Iizima, M.; Kumamoto, A.; Brautigam, D.; Rich, F.

2007-12-01

In order to investigate the equatorial source of subauroral ion drifts (SAID) and its association with the plasmapause position, multi-spacecraft measurements of SAID are presented using the CRRES, Akebono, and DMSP. Direct measurement of the convection electric field and plasmapause density close to the equator is measured by the electric field instrument onboard the CRRES satellite, and the plasmasheet electrons and low energy part of the ring current ions are measured by the low energy plasma instrument. The CRRES satellite is on the dusk inner magnetosphere, and the DMSP-F8 and Akebono satellites are approximately on the same field line. Associated with a substorm onset at 16:40 UT on February 20, 1991, the DMSP-F8 satellite at 19 MLT measures SAID with a maximum westward velocity of 1,500 m/s. The CRRES satellite is on outbound in the inner magnetosphere at ~21 MLT and ~5 RE at the onset of the substorm. It measures increase of DC electric field with 0.4 mV/m in the plasmasphere just after the substorm onset. Thirty minutes later, injection of ring current ions are observed in the plasmasphere with Bz decrease. After the crossing of the plasmapause, the electric field increases to 0.8 mV/m. At the same time, the spacecraft enters the plasmasheet, and the DC electric field disappears. The same time sequence is also identified in other SAID events detected on the dusk inner magnetosphere. The above CRRES measurement indicates that DC electric field is intensified in a narrow region between the ring current and electron plasmasheet after the onset of the substorm. Although the E*B drift points sunward in this region, this region with enhanced electric field is filled with plasmaspheric plasma without abrupt density change. The position where the convection electric field is equal to the corotation electric field locates inside the plasmapause. The plasmapause coincides with inner edge of the plasmasheet. This association suggests that the plasmaspheric plasma is depleted by the plasmasheet electrons, possibly by the enhanced E*B drift earthward of the plasmasheet. During the SAID event on 16:40 UT on February 20, 1991, the Akebono satellite was approximately on the same field line of the CRRES satellite (21 MLT and 5 RE) 40 minutes later the substorm onset. It measures enhancement of electric field with 2 mV/m between L=5 and 6. The inner edge of the electric field corresponds to the inner edge of ring current ions, and the outer edge coincides with the plasmasheet electrons. This signature of the electric field intensification in the charge-separated region is in accordance with the CRRES measurement. This study has clarified that the equatorial source of SAID electric fields is charge separation of ring current ions and plasmasheet electrons by electric field associated with substorms. This is consistent with the theoretical study by Southwood and Wolf [1978] and low-altitude measurements by Anderson et al. [2001] by that the charge separation provides current and voltage sources and the electric field is increased by the low conductance of the subauroral ionosphere.

Unusual refilling of the slot region between the Van Allen radiation belts

NASA Astrophysics Data System (ADS)

Yang, X.; Yu, J.; Ni, B.; Zhang, Y.; Zhang, X.

2017-12-01

Using multi-satellite measurements, the dynamics of relativistic electrons in the slot region are investigated from 2000 to 2011. The dependences of relativistic electron enhancements in the slot region on interplanetary and magnetospheric conditions are researched. It is resulted that the relativistic electron enhancements in the slot region occurred under remarkable interplanetary and magnetospheric conditions. A uniquely strong and long-lived relativistic electron slot region refilling event from November 2004 to January 2005 is studied especially. Both empirically modeled and observationally estimated plasmapause locations demonstrate that the plasmasphere eroded significantly prior to the enhancement phase of this event. The estimated diffusion coefficients indicate that the radial diffusion due to ULF waves is insufficient to account for the observed enhancement of slot region electrons. However, the diffusion coefficients evaluated using the distribution of chorus wave intensities derived from low-altitude POES electron observations indicate that the local acceleration induced by chorus could account for the major feature of observed enhancement outside the plasmapause. When the plasmasphere recovered, the refilled slot region was enveloped inside the plasmapause. In the plasmasphere, while the efficiency of hiss scattering loss increases by including unusually low frequency hiss waves, the interaction with hiss alone cannot fully explain the decay of this event, especially at higher energies, which suggests that EMIC waves contribute to the relativistic electron loss process at such low L-shells for this refilling event.

Micropulsations in the electric field near the plasmapause, observed by Isee 1

NASA Technical Reports Server (NTRS)

Moe, T. E.; Maynard, N. C.; Heppner, J. P.

1980-01-01

The results of a survey of occurrence of micropulsations near and inside the plasmapause, made on the basis of 1 year of data from the double probe electric field instrument on Isee 1, are presented. It is reported that the observed pulsations are classified as Pc 3 and P 2, and that one single Pc 1 event is observed. It is found that Pc 3 events are common during the local day, with a maximum percentage of occurrence as high as 72 in the morning hours. Attention is given to Pi 2 events showing that they are concentrated on the local nightside. Finally, it is noted that pulsations in the Pc 1 range appear on only one inbound pass, which makes the Pc 1 a rare phenomenon at low and moderate latitudes in the plasmasphere.

Pc-5 wave power in the plasmasphere and trough: CRRES observations

NASA Astrophysics Data System (ADS)

Hartinger, M.; Moldwin, M.; Angelopoulos, V.; Takahashi, K.; Singer, H. J.; Anderson, R. R.

2009-12-01

The CRRES (Combined Release and Radiation Effects Satellite) mission provides an opportunity to study the distribution of MHD wave power in the inner magnetosphere both inside the high-density plasmasphere and in the low-density trough. We present a statistical survey of Pc-5 wave power using CRRES magnetometer and plasma wave data separated into plasmasphere and trough intervals. Using a database of plasmapause crossings, we examined differences in power spectral density between the plasmasphere and trough regions. We found significant differences between the plasmasphere and trough in the radial profiles of Pc-5 wave power. On average, wave power was higher in the trough, but the difference in power depended on magnetic local time. Our study shows that determining the plasmapause location is important for understanding and modeling the MHD wave environment in the Pc-5 frequency band.

Electromagnetic radiation trapped in the magnetosphere above the plasma frequency

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Shaw, R. R.

1973-01-01

An electromagnetic noise band is frequently observed in the outer magnetosphere by the Imp 6 spacecraft at frequencies from about 5 to 20 kHz. This noise band generally extends throughout the region from near the plasmapause boundary to near the magnetopause boundary. The noise typically has a broadband field strength of about 5 microvolts/meter. The noise band often has a sharp lower cutoff frequency at about 5 to 10 kHz, and this cutoff has been identified as the local electron plasma frequency. Since the plasma frequency in the plasmasphere and solar wind is usually above 20 kHz, it is concluded that this noise must be trapped in the low-density region between the plasmapause and magnetopause boundaries. The noise bands often contain a harmonic frequency structure which suggests that the radiation is associated with harmonics of the electron cyclotron frequency.

Electrostatic instability of ring current protons beyond the plasmapause during injection events

NASA Technical Reports Server (NTRS)

Coroniti, F. V.; Fredricks, R. W.; White, R.

1972-01-01

The stability of ring current protons with an injection spectrum modeled by an m = 2 mirror distribution function was examined for typical ring current parameters. It was found that the high frequency loss cone mode can be excited at wave numbers K lambda sub Di about = to 0.1 to 0.5, at frequencies omega about = to (0.2 to 0.6) omega sub pi and with growth rates up to gamma/omega about = to 0.03. These waves interact with the main body of the proton distribution and propagate nearly perpendicular to the local magnetic field. Cold particle partial densities tend to reduce the growth rate so that the waves are quenched at or near to the plasmapause boundary. Wave e-folding lengths are comparable to 0.1 R sub e, compared to the value of about 4 R sub e found for ion cyclotron waves at the same plasma conditions.

Magnetospheric electron density measurements from upper hybrid resonance noise observed by IMP-6

NASA Technical Reports Server (NTRS)

Shaw, R. R.; Gurnett, D. A.

1972-01-01

A band of natural radio noise between the local electron plasma frequency and the upper hybrid resonance frequency is observed by the IMP-6 satellite. The band exists over a large range of geocentric radial distances extending from inside the plasmapause boundary to greater than 10 earth radii in the outer magnetosphere. The center frequency of the noise band decreases with increasing radial distance, and changes abruptly at the plasmapause boundary. The broadband electric field strength of this noise is very small, seldom exceeding 10 microvolts/meter, and probably could not be detected without using long electric antennas of IMP-6. It is believed that this noise is produced by incoherent Cerenkov emission from super-thermal electrons. In some cases a second very narrow noise band was observed at a frequency slightly above the second harmonic of the electron gyrofrequency.

Composition measurements of the topside ionosphere using a magnetic mass spectrometer, ion mass spectrometer on ISIS-2 spacecraft

NASA Technical Reports Server (NTRS)

Hoffman, J. H.

1975-01-01

The ion mass spectrometer (IMS) on the ISIS-II satellite is described; it measures the composition and distribution of positive ions in the earth's ionosphere in the mass range of 1 to 64 atomic mass units. Significant data were received which show a wide variation in ion composition at night near the equator and in the daytime poleward of the plasmapause. It was found that these data enable further study of the polar wind and that the experiment produced timely data during the August, 1972 magnetic storm to show the development of a unique ionosphere above the plasmapause during the period of the storm. The scientific objectives and results of the experiment, the technical description of the instrument, a bibliography with sample papers attached, and a summary of recommendations for further study are presented.

A plasmapause-like density boundary at high latitudes in Saturn's magnetosphere

NASA Astrophysics Data System (ADS)

Gurnett, D. A.; Persoon, A. M.; Kopf, A. J.; Kurth, W. S.; Morooka, M. W.; Wahlund, J.-E.; Khurana, K. K.; Dougherty, M. K.; Mitchell, D. G.; Krimigis, S. M.; Krupp, N.

2010-08-01

Here we report the discovery of a well-defined plasma density boundary at high latitudes in Saturn's magnetosphere. The boundary separates a region of relatively high density at L less than about 8 to 15 from a region with densities nearly three orders of magnitude lower at higher L values. Magnetic field measurements show that strong field-aligned currents, probably associated with the aurora, are located just inside the boundary. Analyses of the anisotropy of energetic electrons show that the magnetic field lines are usually closed inside the boundary and open outside the boundary, although exceptions sometimes occur. The location of the boundary is also modulated at the ˜10.6 to 10.8 hr rotational period of the planet. Many of these characteristics are similar to those predicted by Brice and Ioannidis for the plasmapause at a strongly magnetized, rapidly rotating planet such as Saturn.

Revisiting the Inner Magnetospheric Oxygen Torus with DE 1 RIMS

NASA Technical Reports Server (NTRS)

Gallagher, D. L.; Goldstein, J.; Craven, P. D.; Comfort, R. H.

2016-01-01

Nearly 35 years ago direct observations of cold plasmaspheric ions found enhanced O(+), O(++), and even N(+) densities in the outer plasmasphere, in particular during storm recovery conditions. Enhancements were seen inside or just outside of the plasmapause at all magnetic local times. Whereas nominal O(+) concentrations were found to be 1% or less inside the plasmasphere, enhanced O(+) in the vicinity of the plasmapause was found to reach densities comparable to H(+). Enhanced ion outflow (including oxygen) from high latitudes has also become part of our picture of storm-time phenomena. More recently it has become apparent that high latitude outflow is a source of inner magnetospheric warm ions that convect into morning and afternoon local times, to form what we now call the warm plasma cloak. Low to middle latitude ionospheric outflow and high latitude outflow are thought to result from very different processes and can be expected to contribute differently as a function of conditions and locations to the dynamic processes of energy and particle transport in the inner magnetosphere. Given the apparent proximity of their delivery to the vicinity of the plasmapause during plasmaspheric refilling conditions it becomes worthwhile to question the origin of the oxygen torus and its role in this region. While the observations do not yet exist to settle this question, there are measurements that contribute to the discussion in the new emerging context of cold plasma in the inner magnetosphere. In this paper we present and discuss DE 1 RIMS derived ion densities and temperatures that contribute to answering these outstanding questions about the origin and dynamics of the oxygen torus.

A long-lived refilling event of the slot region between the Van Allen radiation belts from Nov 2004 to Jan 2005

NASA Astrophysics Data System (ADS)

Yang, X.

2015-12-01

A powerful relativistic electron enhancement in the slot region between the inner and outer radiation belts is investigated by multi-satellites measurements. The measurement from Space Particle Component Detectors (SPCDs) aboard Fengyun-1 indicates that the relativistic electron (>1.6MeV) flux began to enhance obviously on early 10 November with the flux peak fixed at L~3.0. In the next day, the relativistic electron populations increased dramatically. Subsequently, the flux had been enhancing slowly, but unceasingly, until 17 November, and the maximum flux reached up to 7.8×104 cm-2·sr-1·s-1 at last. The flux peak fixed at L~3.0 and the very slow decay rate in this event make it to be an unusual long-lived slot region refilling event. We trace the cause of the event back to the interplanetary environment and find that there were two evident magnetic cloud constructions: dramatically enhanced magnetic field strength and long and smooth rotation of field vector from late 7 to 8 November and from late 9 to 10 November, respectively; solar wind speed increased in 'step-like' fashion on late 7 November and persisted the level of high speed >560 km·s-1 for about 124 hours. Owed to the interplanetary disturbances, very strong magnetic storms and substorms occurred in the magnetosphere. Responding to the extraordinarily magnetic perturbations, the plasmasphere shrank sharply. The location of plasmapause inferred from Dst indicates that the plasmapause shrank inward to as low as L~2.5. On account of these magnetospheric conditions, strong chorus emissions are expected near the earth. In fact, the STAFF on Cluster mission measured intensive whistler mode chorus emissions on 10 and 12 November, corresponding to the period of the remarkable enhancement of relativistic electron. Furthermore, we investigate the radial profile of phase space density (PSD) by electron flux from multi-satellites, and the evolution of the phase space density profile reveals that the local acceleration by whistler mode chorus could be the important mechanism in this event. The movement of the inferred plasmapause location indicates that the enhanced outer zone is divided into two portions by the plasmapause and the slow loss rate in the plasmasphere due to hiss primarily contributed to the long-lived characteristic of this event.

Formation of the oxygen torus in the inner magnetosphere: Van Allen Probes observations

DOE PAGES

Nose, Masahito; Oimatsu, S.; Keika, K.; ...

2015-02-19

Here we study the formation process of an oxygen torus during the 12–15 November 2012 magnetic storm, using the magnetic field and plasma wave data obtained by Van Allen Probes. We estimate the local plasma mass density (ρ L) and the local electron number density (n eL) from the resonant frequencies of standing Alfvén waves and the upper hybrid resonance band. The average ion mass (M) can be calculated by M ~ ρ L/n eL under the assumption of quasi-neutrality of plasma. During the storm recovery phase, both Probe A and Probe B observe the oxygen torus at L =more » 3.0–4.0 and L = 3.7–4.5, respectively, on the morning side. The oxygen torus has M = 4.5–8 amu and extends around the plasmapause that is identified at L~3.2–3.9. We find that during the initial phase, M is 4–7 amu throughout the plasma trough and remains at ~1 amu in the plasmasphere, implying that ionospheric O + ions are supplied into the inner magnetosphere already in the initial phase of the magnetic storm. Numerical calculation under a decrease of the convection electric field reveals that some of thermal O + ions distributed throughout the plasma trough are trapped within the expanded plasmasphere, whereas some of them drift around the plasmapause on the dawnside. This creates the oxygen torus spreading near the plasmapause, which is consistent with the Van Allen Probes observations. We conclude that the oxygen torus identified in this study favors the formation scenario of supplying O + in the inner magnetosphere during the initial phase and subsequent drift during the recovery phase.« less

Latitudinal dependence on the frequency of Pi2 pulsations near the plasmapause using THEMIS satellites and Asian-Oceanian SuperDARN radars

NASA Astrophysics Data System (ADS)

Teramoto, Mariko; Nishitani, Nozomu; Nishimura, Yukitoshi; Nagatsuma, Tsutomu

2016-02-01

We herein describe a harmonic Pi2 wave that started at 09:12 UT on August 19, 2010, with data that were obtained simultaneously at 19:00-20:00 MLT by three mid-latitude Asian-Oceanian Super Dual Auroral Radar Network (SuperDARN) radars (Unwin, Tiger, and Hokkaido radars), three Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites (THEMIS A, THEMIS D, and THEMIS E), and ground-based magnetometers at low and high latitudes. All THEMIS satellites, which were located in the plasmasphere, observed Pi2 pulsations dominantly in the magnetic compressional ( B //) and electric azimuthal ( E A) components, i.e., the fast-mode component. The spectrum of Pi2 pulsations in the B // and E A components contained two spectral peaks at approximately 12 to 14 mHz ( f 1, fundamental) and 23 to 25 mHz ( f 2, second harmonic). The Poynting flux derived from the electric and magnetic fields indicated that these pulsations were waves propagating earthward and duskward. Doppler variations ( V) from the 6-s or 8-s resolution camping beams of the Tiger and Unwin SuperDARN radars, which are associated with Pi2 pulsations in the eastward electric field component in the ionosphere, observed Pi2 pulsations within and near the footprint of the plasmapause, whose location was estimated by the THEMIS satellites. The latitudinal profile of f 2 power normalized by f 1 power for Doppler velocities indicated that the enhancement of the normalized f 2 power was the largest near the plasmapause at an altitude-adjusted corrected geomagnetic (AACGM) latitude of 60° to 65°. Based on these features, we suggest that compressional waves propagate duskward away from the midnight sector, where the harmonic cavity mode is generated.

Jikiken /EXOS-B/ observation of Siple transmissions

NASA Technical Reports Server (NTRS)

Kimura, I.; Matsumoto, H.; Hashimoto, K.; Mukai, T.; Helliwell, R. A.; Bell, T. F.; Inan, U. S.; Katsufrakis, J. P.

1981-01-01

Preliminary results of observations by the Japanese magnetospheric satellite Jikiken (EXOS-B) of Siple transmissions and VLF emissions triggered by the Siple signals are reviewed. The experiments discussed were carried out in July, August, and September of 1979 and in December 1979 and January 1980. Only four events concentrated within the period from August 14 to 18 were found in which triggered emissions were associated with Siple transmissions. The electron distributions observed on the equatorial crossing passes, when Siple triggered emissions were detected, suggest that the cyclotron resonance condition is satisfied for Siple signals and electrons of energy around 1 keV or less, provided the interaction region is inside the plasmapause. It is noted that if these emissions were generated outside the plasmapause, electron energies much higher than 10 keV would be necessary for the cyclotron interaction, which were above the range of the measurements. For the high latitude passes of August 14 and 17, the electron fluxes were found to be very small.

Ray-tracing studies and path-integrated gains of ELF unducted whistler mode waves in the earth's magnetosphere

NASA Technical Reports Server (NTRS)

Huang, C. Y.; Goertz, C. K.

1983-01-01

Gyroresonance and Landau resonance interactions between unducted low-frequency whistler waves and trapped electrons in the earth's plasmasphere have been studied. Ray paths for waves launched near the plasmapause have been traced. In agreement with recent findings by Thorne et al. (1979), waves have been found which return through the equatorial zone with field-aligned wave normal angles. However, when the growth along the ray path is calculated for such waves, assuming an electron distribution function of the form E exp -n sin exp m alpha, it is found that for all the waves considered, the local growth rate becomes negative before plasmapause reflection, limiting the total gain to small values. Most waves reach zero gain before reflection. This is the result of Landau damping at oblique propagation angles, which necessarily occurs before reflection can take place. It is concluded that the concept of cyclic ray paths does not provide an explanation for the generation of unguided plasmaspheric hiss.

Plasma and electric field boundaries at high and low altitudes on July 29, 1977

NASA Technical Reports Server (NTRS)

Fennell, J. F.; Johnson, R. G.; Young, D. T.; Torbert, R. B.; Moore, T. E.

1982-01-01

Hot plasma observations at high and low altitudes were compared. The plasma ion composition at high altitudes outside the plasmasphere was 0+. Heavy ions were also observed at low altitudes outside the plasmasphere. It is shown that at times these ions are found well below the plasmapause inside the plasmasphere. Comparisons of the low altitude plasma and dc electric fields show that the outer limits of the plasmasphere is not always corotating at the low L-shells. The corotation boundary, the estimated plasmapause boundary at the boundary of the inner edge of plasma sheet ions were at the same position. The inner edge of plasma sheet electrons is observed at higher latitudes than the plasmasphere boundary during disturbed times. The inner edge of the plasma sheaths shows a strong dawn to dusk asymmetry. At the same time the inner edge of the ring current and plasma sheath also moves to high latitudes reflecting an apparent inflation of the magnetosphere.

Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes

DOE PAGES

Xiao, Fuliang; Zhou, Qinghua; He, Yihua; ...

2015-09-11

During the small storm on 14–15 April 2014, Van Allen Probe A measured a continuously distinct proton ring distribution and enhanced magnetosonic (MS) waves along its orbit outside the plasmapause. Inside the plasmasphere, strong MS waves were still present but the distinct proton ring distribution was falling steeply with distance. We adopt a sum of subtracted bi-Maxwellian components to model the observed proton ring distribution and simulate the wave trajectory and growth. MS waves at first propagate toward lower L shells outside the plasmasphere, with rapidly increasing path gains related to the continuous proton ring distribution. The waves then graduallymore » cross the plasmapause into the deep plasmasphere, with almost unchanged path gains due to the falling proton ring distribution and higher ambient density. These results present the first report on how MS waves penetrate into the plasmasphere with the aid of the continuous proton ring distributions during weak geomagnetic activities.« less

Generation of nonthermal continuum radiation in the magnetosphere

NASA Technical Reports Server (NTRS)

Okuda, H.; Chance, M. S.; Ashour-Abdalla, M.; Kurth, W. S.

1982-01-01

Generation of electromagnetic continuum radiation from electrostatic fluctuations near the upper hybrid resonance frequency has been calculated by using cold plasma theory in an inhomogeneous plasma near the plasmapause. It is shown that both the polarization and the amplitude of electromagnetic radiation are in good quantitative agreement with spacecraft observations for nonthermal continuum radiation.

Helium on Venus - Implications for uranium and thorium

NASA Technical Reports Server (NTRS)

Prather, M. J.; Mcelroy, M. B.

1983-01-01

Helium is removed at an average rate of 10 to the 6th atoms per square centimeter per second from Venus's atmosphere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on earth, suggesting comparable abundances of crustal uranium and thorium.

Quantifying the relationship between the plasmapause and the inner boundary of small-scale field-aligned currents, as deduced from Swarm observations

NASA Astrophysics Data System (ADS)

Heilig, Balázs; Lühr, Hermann

2018-04-01

This paper presents a statistical study of the equatorward boundary of small-scale field-aligned currents (SSFACs) and investigates the relation between this boundary and the plasmapause (PP). The PP data used for validation were derived from in situ electron density observations of NASA's Van Allen Probes. We confirmed the findings of a previous study by the same authors obtained from the observations of the CHAMP satellite SSFAC and the NASA IMAGE satellite PP detections, namely that the two boundaries respond similarly to changes in geomagnetic activity, and they are closely located in the near midnight MLT sector, suggesting a dynamic linkage. Dayside PP correlates with the delayed time history of the SSFAC boundary. We interpreted this behaviour as a direct consequence of co-rotation: the new PP, formed on the night side, propagates to the dayside by rotating with Earth. This finding paves the way toward an efficient PP monitoring tool based on an SSFAC index derived from vector magnetic field observations at low-Earth orbit.

Web-based Tool Suite for Plasmasphere Information Discovery

NASA Astrophysics Data System (ADS)

Newman, T. S.; Wang, C.; Gallagher, D. L.

2005-12-01

A suite of tools that enable discovery of terrestrial plasmasphere characteristics from NASA IMAGE Extreme Ultra Violet (EUV) images is described. The tool suite is web-accessible, allowing easy remote access without the need for any software installation on the user's computer. The features supported by the tool include reconstruction of the plasmasphere plasma density distribution from a short sequence of EUV images, semi-automated selection of the plasmapause boundary in an EUV image, and mapping of the selected boundary to the geomagnetic equatorial plane. EUV image upload and result download is also supported. The tool suite's plasmapause mapping feature is achieved via the Roelof and Skinner (2000) Edge Algorithm. The plasma density reconstruction is achieved through a tomographic technique that exploits physical constraints to allow for a moderate resolution result. The tool suite's software architecture uses Java Server Pages (JSP) and Java Applets on the front side for user-software interaction and Java Servlets on the server side for task execution. The compute-intensive components of the tool suite are implemented in C++ and invoked by the server via Java Native Interface (JNI).

The noon and midnight mid-latitude trough as seen by Ariel 4

NASA Technical Reports Server (NTRS)

Tulunay, Y. K.; Grebowsky, J. M.

1978-01-01

The electron density data returned by the polar orbiting satellites Ariel 3 and Ariel 4 revealed that the midlatitude trough is one of the distinct large-scale features of the ionosphere at about 550 km. Recent work (e.g., Tulunay and Grebowsky, 1975) on the data included the investigation of the temporal development of the latitudinal position of the midlatitude electron density trough at dawn and dusk during the large magnetic storms of May 1967 and May 1972. Model calculations which assumed that the equatorial convection E-field varies in step with the Kp index reproduced on the average the observed behavior. In the present paper, trough observations made at noon and midnight during the period, 12-21 December 1971 which encompassed a relatively large magnetic storm are discussed. In this context, model calculations have been employed as a guide of average approximations of the actual situation in predicting the plasmapause location. It is also shown that the trough observed on the noon passes is not generally plasmapause-related as the nightside troughs are expected to be.

First radar observations in the vicinity of the plasmapause of pulsed ionospheric flows generated by bursty bulk flows

NASA Astrophysics Data System (ADS)

Frissell, N. A.; Baker, J. B. H.; Ruohoniemi, J. M.; Clausen, L. B. N.; Kale, Z. C.; Rae, I. J.; Kepko, L.; Oksavik, K.; Greenwald, R. A.; West, M. L.

2011-01-01

Recent expansion of the SuperDARN network to mid-latitudes and the addition of a new high-time resolution mode provides new opportunities to observe mid-latitude ultra-low frequency waves and other ionospheric sub-auroral features at high temporal resolution. On 22 February 2008, the Blackstone SuperDARN radar and THEMIS ground magnetometers simultaneously observed substorm Pi2 pulsations. Similarities in measurements from the Blackstone radar and a magnetometer at Remus suggest a common generating mechanism. Cross-phase analysis of magnetometer data places these measurements at the ionospheric projection of the plasmapause, while fine spatial and temporal details of the radar data show evidence of field line compressions. About 1 min prior to ground Pi2 observation, 2 Earthward-moving Bursty Bulk Flows (BBFs) were observed by THEMIS probes D and E in the near-Earth plasma sheet. We conclude that the first 2 pulses of the Pi2s observed at Blackstone and Remus result from compressional energy generated by BBFs braking against the magnetospheric dipolar region.

A survey of plasma irregularities as seen by the midlatitude Blackstone SuperDARN radar

NASA Astrophysics Data System (ADS)

Ribeiro, A. J.; Ruohoniemi, J. M.; Baker, J. B. H.; Clausen, L. B. N.; Greenwald, R. A.; Lester, M.

2012-02-01

The Super Dual Auroral Radar Network (SuperDARN) is a chain of HF radars that monitor plasma dynamics in the ionosphere. In recent years, SuperDARN has expanded to midlatitudes in order to provide enhanced coverage during geomagnetically active periods. A new type of backscatter from F region plasma irregularities with low Doppler velocity has been frequently observed on the nightside during quiescent conditions. Using three years of data from the Blackstone, VA radar, we have implemented a method for extracting this new type of backscatter from routine observations. We have statistically characterized the occurrence properties of the Sub Auroral Ionospheric Scatter (SAIS) events, including the latitudinal relationships to the equatorward edge of the auroral oval and the ionospheric projection of the plasmapause. We find that the backscatter is confined to local night, occurs on ≈70% of nights, is fixed in geomagnetic latitude, and is equatorward of both the auroral region and the plasmapause boundary. We conclude that SAIS irregularities are observed within a range of latitudes that is conjugate to the inner magnetosphere (plasmasphere).

Self-Consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves: Waves in Multi-Ion Magnetosphere

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.

2006-01-01

The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves (Khazanov et al., 2003) is presented In order to adequately take into account wave propagation and refraction in a multi-ion magnetosphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate the spatial, temporal, and spectral evolution of the ring current and of electromagnetic ion cyclotron waves To demonstrate the effects of EMIC wave propagation and refraction on the wave energy distribution and evolution, we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, owing to the density gradient at the plasmapause, the net wave refraction is suppressed, and He+-mode grows preferably at the plasmapause. This result is in total agreement with previous ray tracing studies and is very clearly found in presented B field spectrograms. Second, comparison of global wave distributions with the results from another ring current model (Kozyra et al., 1997) reveals that this new model provides more intense and more highly plasmapause-organized wave distributions during the May 1998 storm period Finally, it is found that He(+)-mode energy distributions are not Gaussian distributions and most important that wave energy can occupy not only the region of generation, i.e., the region of small wave normal angles, but all wave normal angles, including those to near 90 . The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping and subsequent downward heat transport and excitation of stable auroral red arcs.

Self-Consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 1; Waves in Multi Ion Magnetosphere

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gumayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.

2006-01-01

The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves [Khazanov et al., 2003] is presented. In order to adequately take into account the wave propagation and refraction in a multi-ion plasmasphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate spatial, temporal, and spectral evolutions of the ring current and electromagnetic ion cyclotron waves. To demonstrate the effects of EMIC wave propagation and refraction on the EMIC wave energy distributions and evolution we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, due to the density gradient at the plasmapause, the net wave refraction is suppressed, and He(+)-mode grows preferably at plasmapause. This result is in a total agreement with the previous ray tracing studies, and very clear observed in presented B-field spectrograms. Second, comparison the global wave distributions with the results from other ring current model [Kozyra et al., 1997] reveals that our model provides more intense and higher plasmapause organized distributions during the May, 1998 storm period. Finally, the found He(+)-mode energy distributions are not Gaussian distributions, and most important that wave energy can occupy not only the region of generation, i. e. the region of small wave normal angles, but the entire wave normal angle region and even only the region near 90 degrees. The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping, and subsequent downward heat transport and excitation of stable auroral red arcs.

Loss of oxygen from Venus

NASA Astrophysics Data System (ADS)

McElroy, M. B.; Prather, M. J.; Rodriguez, J. M.

1982-06-01

Ionization of thermal and nonthermal oxygen atoms above the plasmapause on Venus supplies an escape flux for O averaging 6 x 10 to the 6th atoms/sq cm-sec. Hydrogen and oxygen atoms escape with stoichiometry characteristic of water. It is argued that escape of H is controlled by the oxidation state of the atmosphere, regulated by escape of O.

Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

NASA Astrophysics Data System (ADS)

Décréau, Pierrette; Kougblénou, Séna; Lointier, Guillaume; Rauch, Jean Louis; Trotignon, Jean Gabriel; Vallières, Xavier; Canu, Patrick; Rochel Grimald, Sandrine; El-Lemdani Mazouz, Farida; Darrouzet, Fabien

2014-05-01

The non-thermal continuum (NTC) radiation is a radio wave produced within the magnetosphere of a planet. It has been observed in space around Earth since the '70s, and within the magnetospheres of other planets since the late '80s. A new study using ESA's Cluster mission has shown improved precision in determining the source of various radio emissions produced by the Earth. The experiment involved tilting one of the four identical Cluster spacecraft to measure the electric field of this emission in three dimensions for the first time. Our analysis of a NTC case event pinpointed a small deviation from the generally assumed (circular) polarization of this emission. We show that classical triangulation, in this case using three of the spacecraft located thousands of kilometres apart, can lead to an erroneous source location. A second method, using the new 3D electric field measurements, indicated a source located along the plasmapause at medium geomagnetic latitude, far away from the source location estimated by triangulation. Cluster observations reveal that this NTC source emits from the flank of the plasmapause towards the polar cap. Understanding the source of NTC waves will help with the broader understanding of their generation, amplification, and propagation.

Kilometric Continuum Radiation

NASA Technical Reports Server (NTRS)

Green, James L.; Boardsen, Scott

2006-01-01

Kilometric continuum (KC) is the high frequency component (approximately 100 kHz to approximately 800 kHz) of nonthermal continuum (NTC). Unlike the lower frequency portion of NTC (approximately 5 kHz to approximately 100 kHz) whose source is around the dawn sector, the source of KC occurs at all magnetic local times. The latitudinal beaming of KC as observed by GEOTAIL is, for most events, restricted to plus or minus 15 degrees magnetic latitude. KC has been observed during periods of both low and strong geomagnetic activity, with no significant correlation of wave intensity with K(sub p), index. However statistically the maximum observed frequency of KC emission tends to increase with K(sub p) index, the effect is more pronounced around solar maximum, but is also detected near solar minimum. There is strong evidence that the source region of KC is from the equatorial plasmapause during periods when a portion of the plasmapause moves significantly inwards from its nominal position. Case studies have shown that KC emissions are nearly always associated with plasmaspheric notches, shoulders, and tails. There is a recent focus on trying to understand the banded frequency structure of this emission and its relationship to plasmaspheric density ducts and irregularities in the source region.

Charge exchange in a planetary corona - Its effect on the distribution and escape of hydrogen

NASA Technical Reports Server (NTRS)

Chamberlain, J. W.

1977-01-01

The theory for a spherical collisionless planetary corona is extended to include charge-exchange collisions between H(+) and H, which are assumed to constitute intermingled gases with different kinetic temperatures. The treatment is based on the conventional concept of a critical level (or exobase) above which the only collisions considered in the Boltzmann equation are those that resonantly exchange charge. Although the geometry treated is an oversimplification for a real planet, numerical examples are given for an idealized earth and Venus. For earth, an ion temperature of 4 times the neutral temperature, an ion density at the exobase of 14,000 per cu cm, and a plasmapause at 1.5 earth radii will raise the escape flux of H by a factor of 6. The total H above the exobase is changed by less than 1%. For Venus, conditions are examined that would account for the peculiar H distribution observed from Mariner 5. The plasma conditions required are not obviously outrageous by terrestrial standards, but the Mariner 5 ionosphere measurements did not show a high plasmapause at, say, 1.25 or 1.5 planetary radii, a fact that might argue against a charge-exchange model.

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.

Quantitative Simulation of a Magnetospheric Substorm. 3. Plasmaspheric Electric Fields and Evolution of the Plasmapause.

DTIC Science & Technology

1980-01-25

plasmaspheric electric fields during magnetically disturbed periods are based on incoherent scatter radar results fromn St. Santin [ Testud et al., 1975...Millstone Hill radar results showing westward F-region ion drifts of almost 200 m/sec in the afternoon sector on 14 May, 1969. Testud et al. [1975...electrojet (AE) index. Testud et al. [1975] and Blanc et al. £1977] have both presented St. Santin backscatter measurements that show westward and

Behavior of thermal plasma in the ionosphere and magnetosphere

NASA Technical Reports Server (NTRS)

Banks, P. M.; Doupnik, J. R.

1973-01-01

Models of ion flow in the topside ionosphere were developed. These models took both H(+) and O(+) into account and permitted various parameter studies to be made affecting H(+) escape in polar winds. Extensive computer programs were written to display the measured electron density profiles in ways useful to geophysical analysis. The relationship between the location of the plasmapause as it is found in the equatorial plane and the location of the ionospheric trough was also investigated.

Warm and hot electron distribution in the inner magnetosphere and the plasmasheet region related to the magnetospheric indices and the solar wind parameters: a statistical study form the NOAA POES TED and MEPED data

NASA Astrophysics Data System (ADS)

Boscher, Daniel; Rochel Grimald, Sandrine

2013-04-01

Using DMSP satellites, low altitude measurements has demonstrated to give a good picture of the plasmasheet population. The NOAA POES satellites are a constellation of five spacecraft orbiting in a polar orbit between 800 and 850 km and covering a wide L-shell range. They provide fourteen years of data without interruption which allow to make statistical study of the inner magnetosphere and the plasmasheet population. Moreover, since 2002, three of the NOAA POES satellites are located at different local times allowing to deduce the plasmasheet properties, even for huge magnetic activity. This paper present a statistical study of the warm and hot electron density over an energy range [0.16 ; 300] keV and between 1 and 12 Re. We present here maps in Mac Ilwain L paramater / MLT and we use the magnetic indices and solar wind parameter to classify our observations. The results show a clear motion of the plasmapause when Kp increase, which is in agreement with previous results, but it also show changes of the plasmapause shape and strong density variations in the night side sector. Moreover, a clear link between the solar wind parameters, in particular Bz, and the density distribution has been established. Unexpected distributions have been observed in the dayside and will be discussed here.

Storm-Time VLF Emissions Caused by The Solar Wind Disturbances: A Case Study on 8 December 2013

NASA Astrophysics Data System (ADS)

Manninen, J.; Kleimenova, N. G.; Turunen, T.; Gromova, L. I.

2017-08-01

This study is made of temporal variations of the daytime VLF emissions (1-6 kHz) occurred during the moderate magnetic storm (Kp = 6) on 8 December 2013. The storm was associated with the Coronal Mass Ejection (CME). VLF emissions were recorded in the frequency band of 0.2-39 kHz during the dark winter at Kannuslehto (KAN, L 5.5) in Northern Finland. The results were compared with simultaneous variations in the solar wind and Interplanetary Magnetic Field (IMF). It was found that intense VLF chorus started after the pressure jump in solar wind (from 7 to 12 nPa) under the positive IMF Bz. The VLF emissions occurred in two separate frequency bands. The lower frequency (below 2 kHz) band represents the intense long lasting hiss with right-hand polarization, and in the upper frequency band (above 2 kHz) the left-hand polarized hiss bursts occurred during about 1 hour. The plasmasphere was strongly compressed, and due to that KAN was mapped outside of the plasmapause. We suppose that VLF chorus exited in the magnetosphere by the cyclotron instability of the radiation belt electrons. The low frequency chorus was generated outside of the plasmapause and arrived to KAN along the direction of N-S meridian. The high-frequency band was generated inside of the plasmasphere arrived to KAN almost along the meridian.

Relativistic Electron Precipitation: An Observational Study.

DTIC Science & Technology

1980-01-01

al., 1970). These so-called "n + 1/2" waves (- n + 1/2) are found throughout the magnetosphere outside the plasmapause (Kennel et al., 1970; Shaw and...diffusion scattering one requires 2 L D~ . LSD - z ~.(21) 73 where aL = loss cone pitch angle D SD = coefficient for strong diffusion. Equation (20) can be...with substitutions yields a fluctuating field wave amplitude for strong electron diffusion: a." 0- x(23) and 00for f= LSD (24) LRo LRo + For ions

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.

Roles of whistler mode waves and magnetosonic waves in changing the outer radiation belt and the slot region

NASA Astrophysics Data System (ADS)

Li, L. Y.; Yu, J.; Cao, J. B.; Yang, J. Y.; Li, X.; Baker, D. N.; Reeves, G. D.; Spence, H.

2017-05-01

Using the Van Allen Probe long-term (2013-2015) observations and quasi-linear simulations of wave-particle interactions, we examine the combined or competing effects of whistler mode waves (chorus or hiss) and magnetosonic (MS) waves on energetic (<0.5 MeV) and relativistic (>0.5 MeV) electrons inside and outside the plasmasphere. Although whistler mode chorus waves and MS waves can singly or jointly accelerate electrons from the hundreds of keV energy to the MeV energy in the low-density trough, most of the relativistic electron enhancement events are best correlated with the chorus wave emissions outside the plasmapause. Inside the plasmasphere, intense plasmaspheric hiss can cause the net loss of relativistic electrons via persistent pitch angle scattering, regardless of whether MS waves were present or not. The intense hiss waves not only create the energy-dependent electron slot region but also remove a lot of the outer radiation belt electrons when the expanding dayside plasmasphere frequently covers the outer zone. Since whistler mode waves (chorus or hiss) can resonate with more electrons than MS waves, they play dominant roles in changing the outer radiation belt and the slot region. However, MS waves can accelerate the energetic electrons below 400 keV and weaken their loss inside the plasmapause. Thus, MS waves and plasmaspheric hiss generate different competing effects on energetic and relativistic electrons in the high-density plasmasphere.

Relativistic Electron Precipitation Events Observed at Low Altitude During Electromagnetic Ion Cyclotron Wave Activities Identified Near The Equator.

NASA Astrophysics Data System (ADS)

Shin, D. K.; Lee, D. Y.; Noh, S. J.; Cho, J.; Choi, C.; Hwang, J.; Lee, J.

2017-12-01

Statistical significance of the efficiency of electron loss into the atmosphere by EMIC waves has yet not been quantified through observations. To better understand the dynamics of the radiation belt particle, its quantification through observations is indispensable. In this study, we used a large number of the EMIC wave events identified near the equator for which we determined relativistic electron precipitation (REP) events using the observations at low earth orbit satellites (POES satellite series).We focused on the difference between the wave properties, geomagnetic conditions and background states during the EMIC waves between the event group (EMIC wave with REP) and non-event group (EMIC wave without REP). First, for 11.5 % of the EMIC wave events we were able to identify the REP events within an hour of MLT separation from the EMIC wave location. The majority ( 80 %) of the precipitation-inducing EMIC waves were found in 11 - 17 MLT. Second, geomagnetic conditions (most notably AE) are more often stronger for the event group than non-event group. Third, the EMIC waves of a stronger power and/or a longer duration are on average preferred for event group. Lastly, the majority of the EMIC waves with REP lie outside the plasmapause, most often at L being higher by 2 than the plasmapause locations. In conclusion, this is the first time report on a statistical assessment about the extent to which the EMIC waves directly measured in the equator can be responsible for REP and about their distinguishing features.

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

NASA Astrophysics Data System (ADS)

Tetrick, S. S.; Engebretson, M. J.; Posch, J. L.; Olson, C. N.; Smith, C. W.; Denton, R. E.; Thaller, S. A.; Wygant, J. R.; Reeves, G. D.; MacDonald, E. A.; Fennell, J. F.

2017-04-01

We have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 RE relative to the PP. Very few events occurred only within 0.1 RE of the PP, and events with a width in L of < 0.2 RE occurred both inside and outside the PP. Wave occurrence was always associated with high densities of ring current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and compressions of the magnetosphere were more evenly distributed both inside and outside the PP. Superposed epoch analyses of the dependence of wave onset on solar wind dynamic pressure (Psw), the SME (SuperMAG auroral electrojet) index, and the SYM-H index showed that substorm injections and solar wind compressions were temporally closely associated with EMIC wave onset but to an extent that varied with frequency band, magnetic local time, and storm phase, and location relative to the PP. The fact that increases in SME and Psw were less strongly correlated with events at the PP than with other events might suggest that the occurrence of those events was affected by the density gradient.

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.

Venus: ionosphere and atmosphere as measured by dual-frequency radio occultation of mariner v.

PubMed

1967-12-29

Venus has daytime and nighttime ionospheres at the positions probed by radio occulation. The main layers are thin by terrestrial standards, with the nighttime peak concentration of electrons being about two orders of magnitude below that of the daytime peak. Above the nighttime peak were several scale-height regimes extending to a radius of at least 7500, and probably to 9700, kilometers from the center of Venus. Helium and hydrogen at plasma temperatures of 600 degrees to 1100 degrees K seem indicated in the regimes from 6300 to 7500 kilometers, with cooler molecular ions in lower regions. Above the daytime peak a sharp plasmapause was discovered, marking a sudden transition from appreciable ionization concentrations near Venus to the tenuous conditions of the solar wind. This may be indicative of a kind of interaction of the magnetized solar wind with a planetary body that differs from the two different kinds of interaction characterized by Earth and by Moon. For Venus and probably for Mars, the magnetic field of the solar wind may pile up in front of the conducting ionosphere, form an induced magnetosphere that ends at the plasmapause, above which any ionosphere that tends to form is swept away by the shocked solar wind that flows between the stand-off bow-shock and the magnetopause. The neutral atmosphere was also probed and a surface reflection may have been detected, but the data have not yet been studied in detail. Results are consistent with a super-refractive atmosphere, as expected from Soviet measurements near the surface. Thus, two unusual features of Venus can be described in terms of a light trap in the lower atmosphere, and a magnetic trap in the conducting ionosphere.

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

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

Tetrick, S. S.; Engebretson, M. J.; Posch, J. L.

In this paper, we have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 R E relative to the PP. Very few events occurred only within 0.1 R E of the PP, and events with a width in L of < 0.2 R E occurred both inside and outside the PP. Wave occurrence was always associated with high densities of ringmore » current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and compressions of the magnetosphere were more evenly distributed both inside and outside the PP. Superposed epoch analyses of the dependence of wave onset on solar wind dynamic pressure (Psw), the SME (SuperMAG auroral electrojet) index, and the SYM-H index showed that substorm injections and solar wind compressions were temporally closely associated with EMIC wave onset but to an extent that varied with frequency band, magnetic local time, and storm phase, and location relative to the PP. Finally, the fact that increases in SME and Psw were less strongly correlated with events at the PP than with other events might suggest that the occurrence of those events was affected by the density gradient.« less

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

DOE PAGES

Tetrick, S. S.; Engebretson, M. J.; Posch, J. L.; ...

2017-03-17

In this paper, we have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 R E relative to the PP. Very few events occurred only within 0.1 R E of the PP, and events with a width in L of < 0.2 R E occurred both inside and outside the PP. Wave occurrence was always associated with high densities of ringmore » current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and compressions of the magnetosphere were more evenly distributed both inside and outside the PP. Superposed epoch analyses of the dependence of wave onset on solar wind dynamic pressure (Psw), the SME (SuperMAG auroral electrojet) index, and the SYM-H index showed that substorm injections and solar wind compressions were temporally closely associated with EMIC wave onset but to an extent that varied with frequency band, magnetic local time, and storm phase, and location relative to the PP. Finally, the fact that increases in SME and Psw were less strongly correlated with events at the PP than with other events might suggest that the occurrence of those events was affected by the density gradient.« less

Location of EMIC Wave Events Relative to the Plasmapause: Van Allen Probes Observations

NASA Astrophysics Data System (ADS)

Tetrick, S.; Engebretson, M. J.; Posch, J. L.; Kletzing, C.; Smith, C. W.; Wygant, J. R.; Gkioulidou, M.; Reeves, G. D.; Fennell, J. F.

2015-12-01

Many early theoretical studies of electromagnetic ion cyclotron (EMIC) waves generated in Earth's magnetosphere predicted that the equatorial plasmapause (PP) would be a preferred location for their generation. However, several large statistical studies in the past two decades, most notably Fraser and Nguyen [2001], have provided little support for this location. In this study we present a survey of the most intense EMIC waves observed by the EMFISIS fluxgate magnetometer on the Van Allen Probes-A spacecraft (with apogee at 5.9 RE) from its launch through the end of 2014, and have compared their location with simultaneous electron density data obtained by the EFW electric field instrument and ring current ion flux data obtained by the HOPE and RBSPICE instruments. We show distributions of these waves as a function of distance inside or outside the PP as a function of local time sector, frequency band (H+, He+, or both), and timing relative to magnetic storms and substorms. Most EMIC waves in this data set occurred within 1 RE of the PP in all local time sectors, but very few were limited to ± 0.1 RE, and most of these occurred in the 06-12 MLT sector during non-storm conditions. The majority of storm main phase waves in the dusk sector occurred inside the PP. He+ band waves dominated at most local times inside the PP, and H+ band waves were never observed there. Although the presence of elevated fluxes of ring current protons was common to all events, the configuration of lower energy ion populations varied as a function of geomagnetic activity and storm phase.

An association of magnetospheric whistler dispersion characteristics with changes in local plasma density.

NASA Technical Reports Server (NTRS)

Scarf, F. L.; Chappell, C. R.

1973-01-01

We use OGO 5 measurements made within the plasmapause on May 15, 1969, to investigate the possible association between changes in lightning whistler dispersion characteristics and local density fluctuations. It is shown that groups of whistlers with relatively constant dispersions tended to be detected in regions where the local ion concentration was significantly enhanced. It is assumed that these local density fluctuations represent characteristics of large-scale field-aligned variations. The results are then compared with ray refraction estimates appropriate for low-frequency whistler mode propagation (wave components with frequencies comparable to the local lower hybrid frequency) in a nonuniform medium.

Particle simulation of electromagnetic emissions from electrostatic instability driven by an electron ring beam on the density gradient

NASA Astrophysics Data System (ADS)

Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej

2018-04-01

This paper presents the wave mode conversion between electrostatic and electromagnetic waves on the plasma density gradient. We use 2-D electromagnetic code KEMPO2 implemented with the generation of density gradient to simulate such a conversion process. In the dense region, we use ring beam instability to generate electron Bernstein waves and we study the temporal evolution of wave spectra, velocity distributions, Poynting flux, and electric and magnetic energies to observe the wave mode conversion. Such a conversion process can be a source of electromagnetic emissions which are routinely measured by spacecraft on the plasmapause density gradient.

Analysis of magnetometer data/wave signals in the Earth's magnetosphere

NASA Technical Reports Server (NTRS)

Engebretson, Mark J.

1993-01-01

Work on the reduction and analysis of Dynamics Explorer (DE) satellite magnetometer data with special emphasis on the ULF fluctuations and waves evident in such data is described. Research focused on the following: (1) studies of Pc 1 wave packets near the plasmapause; (2) satellite-ground pulsation study; (3) support for studies of ion energization processes; (4) search for Pc 1 wave events in 1981 DE 1 data; (5) study of Pc 3-5 events observed simultaneously by DE 1 and by AMPTE CCE; (6) support for studies of electromagnetic transients on DE 1; and (7) analysis of wave events induced by sudden impulses.

Detailed observations of the source of terrestrial narrowband electromagnetic radiation

NASA Technical Reports Server (NTRS)

Kurth, W. S.

1982-01-01

Detailed observations are presented of a region near the terrestrial plasmapause where narrowband electromagnetic radiation (previously called escaping nonthermal continuum radiation) is being generated. These observations show a direct correspondence between the narrowband radio emissions and electron cyclotron harmonic waves near the upper hybrid resonance frequency. In addition, electromagnetic radiation propagating in the Z-mode is observed in the source region which provides an extremely accurate determination of the electron plasma frequency and, hence, density profile of the source region. The data strongly suggest that electrostatic waves and not Cerenkov radiation are the source of the banded radio emissions and define the coupling which must be described by any viable theory.

Relativistic electron precipitation at International Space Station: Space weather monitoring by Calorimetric Electron Telescope

NASA Astrophysics Data System (ADS)

Kataoka, Ryuho; Asaoka, Yoichi; Torii, Shoji; Terasawa, Toshio; Ozawa, Shunsuke; Tamura, Tadahisa; Shimizu, Yuki; Akaike, Yosui; Mori, Masaki

2016-05-01

The charge detector (CHD) of the Calorimetric Electron Telescope (CALET) on board the International Space Station (ISS) has a huge geometric factor for detecting MeV electrons and is sensitive to relativistic electron precipitation (REP) events. During the first 4 months, CALET CHD observed REP events mainly at the dusk to midnight sector near the plasmapause, where the trapped radiation belt electrons can be efficiently scattered by electromagnetic ion cyclotron (EMIC) waves. Here we show that interesting 5-20 s periodicity regularly exists during the REP events at ISS, which is useful to diagnose the wave-particle interactions associated with the nonlinear wave growth of EMIC-triggered emissions.

AMPTE/CCE observations of the plasma composition below 17 keV during the September 4, 1984 magnetic storm

NASA Technical Reports Server (NTRS)

Shelley, E. G.; Klumpar, D. M.; Peterson, W. K.; Ghielmetti, A.; Balsiger, H.; Geiss, J.; Rosenbauer, H.

1985-01-01

Observations from the Hot Plasma Composition Experiment on the AMPTE/CCE spacecraft during the magnetic storm of 4-5 September 1984 reveal that significant injection of ions of terrestrial origin accompanied the storm development. The compression of the magnetosphere at storm sudden commencement carried the magnetopause inside the CCE orbit clearly revealing the shocked solar wind plasma. A build up of suprathermal ions is observed near the plasmapause during the storm main phase and recovery phase. Pitch angle distributions in the ring current during the main phase show differences between H(+) and O(+) that suggest mass dependent injection, transport and/or loss processes.

Simultaneous equatorial observations of 1- to 30-Hz waves and pitch angle distributions of ring current ions

NASA Technical Reports Server (NTRS)

Taylor, W. W. L.; Lyons, L. R.

1976-01-01

Eighteen events of large-amplitude (0.4-6 gammas) waves which may be propagating in the ion cyclotron mode have een observed by Explorer 45. Comparison with simultaneously measured proton distributions has allowed the events to be divided into two categories. The first category consists of waves accompanied by enhanced ion fluxes apparently injected into the plasmasphere with anisotropic pitch-angle distributions. This simultaneity suggests that these waves may be generated by the observed ring-current ions. Waves in the second category were found near or outside the plasmapause and were not correlated with any identifiable changes in the observed proton distribution. The generation mechanism for these waves remains unknown.

OGO 5 observations of Pc 5 waves - Particle flux modulations

NASA Technical Reports Server (NTRS)

Kokubun, S.; Kivelson, M. G.; Mcpherron, R. L.; Russell, C. T.; West, H. I., Jr.

1977-01-01

An investigation is conducted concerning the modulations of particle fluxes associated with Pc 5 waves in the region beyond the plasmapause. A study of thermal flux modulations indicates that some of the density enhancements observed are not spatial structures but are spurious features caused by temporal flux variations associated with hydromagnetic waves. A resonance model of the energetic particle flux modulations is discussed. Energetic particle modulations are also considered. The reported observations reveal that modulations are dominant at energies of about 100 keV for electrons and at 100 keV to 1 MeV for protons. This may indicate that the bounce resonance interaction is not important for Pc 5 waves.

Effect of parallel refraction on magnetospheric upper hybrid waves

NASA Technical Reports Server (NTRS)

Engel, J.; Kennel, C. F.

1984-01-01

Large amplitude (not less than 10 mV/m) electrostatic plasma waves near the upper hybrid (UH) frequency have been observed from 0 to 50 deg magnetic latitude (MLAT) during satellite plasma-pause crossings. A three-dimensional numerical ray-tracing calculation, based on an electron distribution measured during a GEOS 1 dayside intense upper-hybrid wave event, suggests how UH waves might achieve such large amplitudes away from the geomagnetic equator. Refractive effects largely control the wave amplification and, in particular, the unavoidable refraction due to parallel geomagnetic field gradients restricts growth to levels below those observed. However, a cold electron density gradient parallel to the field can lead to upper hybrid wave growth that can account for the observed emission levels.

Characteristics of thermal and suprathermal ions associated with the dayside plasma trough as measured by the dynamics explorer retarding ion mass spectrometer

NASA Technical Reports Server (NTRS)

Sojka, J. J.; Schunk, R. W.; Johnson, J. F. E.; Waite, J. H.; Chappell, C. R.

1983-01-01

The thermal and suprathermal ion populations present in the refilling regions after a magnetic storm are examined using retarding ion mass spectrometer (RIMS) data from the Dynamics Explorer 1 spacecraft. The RIMS instrument is described, and data are presented and discussed in detail for the outer plasmasphere, plasmapause, depleted dayside magnetosphere, and dayside cusp. Three distinct populations were observed: thermal ions, warm anisotropic plasma, and the polar wind. The characteristics of these populations are considered, including the densities, temperatures, and density ratios. Aspects of the ionospheric plasma outflow are discussed, including the field-aligned flow speed, the ionospheric plasma escape flux, plasmaspheric refilling, and wave-particle phenomena.

An ISEE/Whistler model of equatorial electron density in the magnetosphere

NASA Technical Reports Server (NTRS)

Carpenter, D. L.; Anderson, R. R.

1992-01-01

Attention is given to an empirical model of equatorial electron density in the magnetosphere covering the L range 2.25-8. Although the model is primarily intended for application to the local time interval 00-15 MLT, a way to extend the model to the 15-24-MLT period is presented. The model describes, in piecewise fashion, the 'saturated' plasmasphere, the region of steep plasmapause gradients, and the plasma trough. Within the plasmasphere the model profile can be expressed as logne - Sigma-xi, where x1 = -0.3145L + 3.9043 is the principal or 'reference' term, and additional terms account for: a solar cycle variation with a peak at solar maximum; an annual variation with a December maximum; and a semiannual variation with equinoctial maxima.

Plasmasphere Response: Tutorial and Review of Recent Imaging Results

NASA Astrophysics Data System (ADS)

Goldstein, J.

2006-06-01

The plasmasphere is the cold, dense innermost region of the magnetosphere that is populated by upflow of ionospheric plasma along geomagnetic field lines. Driven directly by dayside magnetopause reconnection, enhanced sunward convection erodes the outer layers of the plasmasphere. Erosion causes the plasmasphere outer boundary, the plasmapause, to move inward on the nightside and outward on the dayside to form plumes of dense plasma extending sunward into the outer magnetosphere. Coupling between the inner magnetosphere and ionosphere can significantly modify the convection field, either enhancing sunward flows near dusk or shielding them on the night side. The plasmaspheric configuration plays a crucial role in the inner magnetosphere; wave-particle interactions inside the plasmasphere can cause scattering and loss of warmer space plasmas such as the ring current and radiation belts.

Motions of charged particles in the Magnetosphere under the influence of a time-varying large scale convection electric field

NASA Technical Reports Server (NTRS)

Smith, P. H.; Bewtra, N. K.; Hoffman, R. A.

1979-01-01

The motions of charged particles under the influence of the geomagnetic and electric fields were quite complex in the region of the inner magnetosphere. The Volland-Stern type large scale convection electric field was used successfully to predict both the plasmapause location and particle enhancements determined from Explorer 45 measurements. A time dependence in this electric field was introduced based on the variation in Kp for actual magnetic storm conditions. The particle trajectories were computed as they change in this time-varying electric field. Several storm fronts of particles of different magnetic moments were allowed to be injected into the inner magnetosphere from L = 10 in the equatorial plane. The motions of these fronts are presented in a movie format.

Observations of proton spectra (1.0 less than or equal to proton energy less than or equal to 300 keV) and pitch angle distributions at the plasmapause

NASA Technical Reports Server (NTRS)

Williams, D. J.; Fritz, T. A.; Konradi, A.

1972-01-01

Detailed proton spectral and pitch angle distribution observations were obtained from two proton detectors and a fluxgate magnetometer flown on Small Scientific Satellite A (Explorer 45). The data of interest are from orbit 99 in-bound occurring on 17 December 1971, some 8 hours prior to the sudden commencement of a magnetic storm. The data are consistent with the initiation of ion cyclotron instability when certain requirements are met. These criteria are met initially at the altitude at which the sudden intensity decrease occurs. However, after the initiation of the instability, the linear theory is unable to explain the further evolution of intensities, pitch angle distributions, and energy spectra of the ring current particles.

High Frequency Analyzer (HFA) of Plasma Wave Experiment (PWE) onboard the Arase spacecraft

NASA Astrophysics Data System (ADS)

Kumamoto, Atsushi; Tsuchiya, Fuminori; Kasahara, Yoshiya; Kasaba, Yasumasa; Kojima, Hirotsugu; Yagitani, Satoshi; Ishisaka, Keigo; Imachi, Tomohiko; Ozaki, Mitsunori; Matsuda, Shoya; Shoji, Masafumi; Matsuoka, Aayako; Katoh, Yuto; Miyoshi, Yoshizumi; Obara, Takahiro

2018-05-01

The High Frequency Analyzer (HFA) is a subsystem of the Plasma Wave Experiment onboard the Arase (ERG) spacecraft. The main purposes of the HFA include (1) determining the electron number density around the spacecraft from observations of upper hybrid resonance (UHR) waves, (2) measuring the electromagnetic field component of whistler-mode chorus in a frequency range above 20 kHz, and (3) observing radio and plasma waves excited in the storm-time magnetosphere. Two components of AC electric fields detected by Wire Probe Antenna and one component of AC magnetic fields detected by Magnetic Search Coils are fed to the HFA. By applying analog and digital signal processing in the HFA, the spectrograms of two electric fields (EE mode) or one electric field and one magnetic field (EB mode) in a frequency range from 10 kHz to 10 MHz are obtained at an interval of 8 s. For the observation of plasmapause, the HFA can also be operated in PP (plasmapause) mode, in which spectrograms of one electric field component below 1 MHz are obtained at an interval of 1 s. In the initial HFA operations from January to July, 2017, the following results are obtained: (1) UHR waves, auroral kilometric radiation (AKR), whistler-mode chorus, electrostatic electron cyclotron harmonic waves, and nonthermal terrestrial continuum radiation were observed by the HFA in geomagnetically quiet and disturbed conditions. (2) In the test operations of the polarization observations on June 10, 2017, the fundamental R-X and L-O mode AKR and the second-harmonic R-X mode AKR from different sources in the northern polar region were observed. (3) The semiautomatic UHR frequency identification by the computer and a human operator was applied to the HFA spectrograms. In the identification by the computer, we used an algorithm for narrowing down the candidates of UHR frequency by checking intensity and bandwidth. Then, the identified UHR frequency by the computer was checked and corrected if needed by the human operator. Electron number density derived from the determined UHR frequency will be useful for the investigation of the storm-time evolution of the plasmasphere and topside ionosphere.[Figure not available: see fulltext.

Convection Electric Field Observations by THEMIS and the Van Allen Probes

NASA Astrophysics Data System (ADS)

Califf, S.; Li, X.; Bonnell, J. W.; Wygant, J. R.; Malaspina, D.; Hartinger, M.; Thaller, S. A.

2013-12-01

We present direct electric field measurements made by THEMIS and the Van Allen Probes in the inner magnetosphere, focusing on the large-scale, near-DC convection electric field. The convection electric field drives plasma Earthward from the tail into the inner magnetosphere, playing a critical role in forming the ring current. Although it is normally shielded deep inside the magnetosphere, during storm times this large-scale electric field can penetrate to low L values (L < 3), eroding the plasmasphere and also providing a mechanism for ~100 keV electron injection into the slot region and inner radiation belt. The relationship of the convection electric field with the plasmasphere is also important for understanding the dynamic outer radiation belt, as the plasmapause boundary has been strongly correlated with the dynamic variation of the outer radiation belt electrons.

Cluster observations of reflected EMIC-triggered emission

NASA Astrophysics Data System (ADS)

Grison, B.; Darrouzet, F.; Santolík, O.; Cornilleau-Wehrlin, N.; Masson, A.

2016-05-01

On 19 March 2001, the Cluster fleet recorded an electromagnetic rising tone on the nightside of the plasmasphere. The emission was found to propagate toward the Earth and toward the magnetic equator at a group velocity of about 200 km/s. The Poynting vector is mainly oblique to the background magnetic field and directed toward the Earth. The propagation angle θk,B0 becomes more oblique with increasing magnetic latitude. Inside each rising tone θk,B0 is more field aligned for higher frequencies. Comparing our results to previous ray tracing analysis we conclude that this emission is a triggered electromagnetic ion cyclotron (EMIC) wave generated at the nightside plasmapause. We detect the wave just after its reflection in the plasmasphere. The reflection makes the tone slope shallower. This process can contribute to the formation of pearl pulsations.

Ray tracing study of rising tone EMIC-triggered emissions

NASA Astrophysics Data System (ADS)

Hanzelka, Miroslav; Santolík, Ondřej; Grison, Benjamin; Cornilleau-Wehrlin, Nicole

2017-04-01

ElectroMagnetic Ion Cyclotron (EMIC) triggered emissions have been subject of extensive theoretical and experimental research in last years. These emissions are characterized by high coherence values and a frequency range of 0.5 - 2.0 Hz, close to local helium gyrofrequency. We perform ray tracing case studies of rising tone EMIC-triggered emissions observed by the Cluster spacecraft in both nightside and dayside regions off the equatorial plane. By comparison of simulated and measured wave properties, namely wave vector orientation, group velocity, dispersion and ellipticity of polarization, we determine possible source locations. Diffusive equilibrium density model and other, semi-empirical models are used with ion composition inferred from cross-over frequencies. Ray tracing simulations are done in cold plasma approximation with inclusion of Landau and cyclotron damping. Various widths, locations and profiles of plasmapause are tested.

Characteristics of electron distributions observed during large amplitude whistler wave events in the magnetosphere

NASA Astrophysics Data System (ADS)

Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Wygant, J.; Breneman, A. W.; Kersten, K.

2010-12-01

We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce ≤ 0.5 and are observed primarily in the radiation belts outside the plasmapause simultaneously with anisotropic electron distributions. We also present an example waveform capture of the largest magnetic field amplitude (≥ 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).

Characteristics of Electron Distributions Observed During Large Amplitude Whistler Wave Events in the Magnetosphere

NASA Technical Reports Server (NTRS)

Wilson, Lynn B., III

2010-01-01

We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce < or = 0.5 and are observed primarily in the radiation belts outside the plasmapause simultaneously with anisotropic electron distributions. We also present an example waveform capture of the largest magnetic field amplitude (> or = 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).

Plasmaspheric Erosion via Plasmasphere Coupling to Ring Current Plasmas: EUV Observations and Modeling

NASA Technical Reports Server (NTRS)

Adrian, M. L.; Gallagher, D. L.; Khazanov, G. V.; Chsang, S. W.; Liemohn, M. W.; Perez, J. D.; Green, J. L.; Sandel, B. R.; Mitchell, D. G.; Mende, S. B.;

Triggered emissions close to the proton gyrofrequency seen by Cluster

NASA Astrophysics Data System (ADS)

Grison, Benjamin; Pickett, Jolene; Omura, Yoshiharu; Santolik, Ondrej; Decreau, Pierrette; Masson, Arnaud; Engebretson, Mark; Cornilleau-Wehrlin, Nicole; Robert, Patrick; Dandouras, Iannis

Electromagnetic ion cyclotron (EMIC) triggered emissions have been recently observed onboard the Cluster spacecraft close to the plasmapause in the equatorial region of the magnetosphere. These waves appear as "risers": electromagnetic structures that have a positive frequency drift with time, i.e., the EMIC analogue of rising frequency whistler mode triggered emissions and chorus waves. In our first results concerning the emission process based on a single event, these risers have the following properties: they propagate away from the direction of the magnetic equator, they have elliptical left-handed polarization corresponding to the transverse Alfven mode, and frequency drifts of about 30 mHz/s. These risers are not common in the Cluster data set. Nevertheless a few other events were found with similar properties. Another interesting preliminary result is the existence of risers with a polarization opposite that of the EMIC triggered emissions and which correspond to the fast magnetosonic mode.

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.

Generation and propagation of electromagnetic waves in the magnetosphere. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Taylor, W. W. L.

1973-01-01

Characteristics of broadband ELF, VLF, and LF emissions in the magnetosphere were calculated assuming incoherent Cerenkov radiation from magnetospheric electrons with energies from 50 eV to 50 keV. Calculations were included to determine the ray paths of the emitted waves. A diffusive equilibrium model of the magnetosphere with an ionosphere, plasmapause, and a centered dipole magnetic field was used. Ray path calculations were done in three dimensions. Using simultaneous energetic electron and VLF data, comparisons were made between calculated and observed VLF hiss. Assuming a wave normal angle six degrees from the resonance cone angle, the calculated spectral densities are both two orders of magnitude below the observed spectral densities. It seems unlikely that VLF hiss is produced by incoherent Cerenkov radiation. The observed spectral shape of V-shaped VLF hiss is similar to that calculated from incoherent Cerenkov radiation.

Generation of Plasma Density Irregularities in the Midlatitude/Subauroral F Region

NASA Astrophysics Data System (ADS)

Mishin, E. V.

2017-12-01

A concise review is given of the current state of the theoretical understanding of the creation of small- and meso-scale plasma density irregularities in the midlatitude/subauroral F region during quiet and disturbed periods. The former are discussed in terms of the temperature gradient instability (TGI) in the vicinity of the ionospheric projection of the plasmapause and the Perkins instability. During active conditions some part of the midlatitude ionosphere becomes the subauroral region dominated by enhanced westward flows (SAPS and SAID) driven by poleward electric fields. Their irregular, often nonlinear wave structure leads to the formation of plasma density irregularities in the plasmasphere and conjugate ionosphere. Here, meso-scale irregularities are due to the positive feedback magnetosphere-ionosphere coupling instability, while small scales resulted from the gradient drift instability (GDI), temperature GDI, and the ion frictional heating instability. The theoretical predictions are compared with satellite observations in the perturbed subauroral geospace.

Electromagnetic ion cyclotron waves observed near the oxygen cyclotron frequency by ISEE 1 and 2

NASA Technical Reports Server (NTRS)

Fraser, B. J.; Samson, J. C.; Hu, Y. D.; Mcpherron, R. L.; Russell, C. T.

1992-01-01

The first results of observations of ion cyclotron waves by the elliptically orbiting ISEE 1 and 2 pair of spacecraft are reported. The most intense waves (8 nT) were observed in the outer plasmasphere where convection drift velocities were largest and the Alfven velocity was a minimum. Wave polarization is predominantly left-handed with propagation almost parallel to the ambient magnetic field, and the spectral slot and polarization reversal predicted by cold plasma propagation theory are identified in the wave data. Computations of the experimental wave spectra during the passage through the plasmapause show that the spectral slots relate to the local plasma parameters, possibly suggesting an ion cyclotron wave growth source near the spacecraft. A regular wave packet structure seen over the first 30 min of the event is attributed to the modulation of this energy source by the Pc 5 waves seen at the same time.

Characterization of Nightside Mid-latitude Irregularities Observed with the Blackstone SuperDARN Radar

NASA Astrophysics Data System (ADS)

Ruohoniemi, J. M.; Ribeiro, A. J.; Baker, J. B.; Greenwald, R. A.; Newell, P. T.

2009-12-01

The new mid-latitude SuperDARN radars at Wallops Island and Blackstone observe strong coherent backscattering on an almost nightly basis from latitudes that appear to be subauroral. One study has demonstrated an excellent correlation with the occurrence of density and temperature gradients within the ionospheric projection of the plasmapause (Greenwald et al., Geophys. Res. Lett. [2006]). We have processed all the data collected with the Blackstone radar since its inception in February 2008 for a characterization of the occurrence and properties of ‘plasmapause’ scatter. We have determined the local time and Kp dependencies of the activity and the relation of the spatial distribution of the irregularities to magnetospheric boundaries and ionospheric density gradients. We establish that the irregularities are a feature of the quiet-time subauroral ionosphere and provide a valuable diagnostic of the electric fields in the inner magnetosphere.

Lower Hybrid Oscillations in Multicomponent Space Plasmas Subjected to Ion Cyclotron Waves

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Krivorutsky, E. N.; Moore, T. E.; Liemohn, M. W.; Horwitz, J. L.

1997-01-01

It is found that in multicomponent plasmas subjected to Alfven or fast magnetosonic waves, such as are observed in regions of the outer plasmasphere and ring current-plasmapause overlap, lower hybrid oscillations are generated. The addition of a minor heavy ion component to a proton-electron plasma significantly lowers the low-frequency electric wave amplitude needed for lower hybrid wave excitation. It is found that the lower hybrid wave energy density level is determined by the nonlinear process of induced scattering by ions and electrons; hydrogen ions in the region of resonant velocities are accelerated; and nonresonant particles are weakly heated due to the induced scattering. For a given example, the light resonant ions have an energy gain factor of 20, leading to the development of a high-energy tail in the H(+) distribution function due to low-frequency waves.

Second harmonic Pi2 pulsation observed near the plasmapause by the Asian-Oceanian SuperDARN radars and THEMIS satellites

NASA Astrophysics Data System (ADS)

Teramoto, M.; Nishitani, N.; Hori, T.; Devlin, J. C.; Angelopoulos, V.; Glassmeier, K.; Clausen, L.; Baumjohann, W.; Bonnell, J. W.; Mozer, F.

2012-12-01

Pi2 pulsations appear on the nightside at substorm onsets. Several studies suggested that transient Alfven waves might contribute to the excitation of Pi2 pulsations at nightside mid and high latitudes. On the other hand, fast mode waves trapped between the ionosphere and plasmapause are responsible for Pi2 pulsations at mid and low latitudes on the nightside. Using the Sweden And Britain auroral Radar Experiment (SABRE) coherent radar at auroral and sub-auroral latitudes, Yeoman et al. [1991] found that the radar could distinguish between these two types of Pi2 pulsations and suggested that the mid latitude region is the transition region of these two types of Pi2 pulsations. We report on one event of Pi2 pulsation starting at 09:12 UT on 19 August 2010 observed simultaneously by the Hokkaido (HOK), Tiger (TIG), and Unwin (UNW) SuperDARN radars and THEMIS-A, -D, -E satellites when they were located in the premidnight sector. The THEMIS satellites observed Pi2 pulsations at 13 mHz predominantly in the compressional and radial components of the magnetic field and the azimuthal component of the electric field when satellites were located at L < 5 inside the plasmasphere. These pulsations had high coherence (~1) with the H-component Pi2 pulsations at a low-latitude ground station, Kakioka (KAK: magnetic latitude 27.47; magnetic longitude 209.2 degrees). The Poynting flux indicates earthward and duskward flux of Pi2 energy. The radars observed oscillations of Doppler velocities at mid latitude while operating in themisscan mode, during which beam 4 of HOK, beam 4 of TIG, and beam 14 of UNW provide 8-s sampling data. These oscillations corresponded to approximately the east-west component of electric field in the ionosphere. Oscillations backscattered form the lower-latitude ionosphere had a predominant frequency at 13 mHz while Pi2 pulsations observed at higher latitude by the radars had predominant frequencies at both 13 and 25 mHz. The power of Doppler velocity oscillations at 25 mHz was greater than that at 13 mHz at 60-65° geomagnetic latitude. These results indicate that a fast mode wave propagating earthward and duskward causes fundamental and second harmonic structures in the plasmasphere. We will present the details of the observation.

Comparison of intense electrostatic waves near f/sub UHR/ with linear instability theory

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

Kurth, W.S.; Frank, L.A.; Gurnett, D.A.

1979-06-01

Intense electrostatic waves beyond the plasmapause have recently been identified at frequencies near the upper hybrid resonance frequency. In addition, the waves occur within a band at an odd, half-harmonic of the local electron gyrofrequency. These bands of electrostatic turbulence are among the most intense waves detected within the earth's magnetosphere. Measurements obtained with the ISEE 1 plasma wave receiver show that the intense waves appear to be intensifications of an electrostatic cyclotron harmonic band near the upper hybrid resonance frequency. A straightforward explanation of intense waves at the upper hybrid resonance frequency exists in the electrostatic multi-cyclotron emission theory.more » For a broad range of plasma parameters nonconvective instability or large spatial growth rates occur within the cyclotron band encompassing the cold upper hybrid frequency. Comparison of spatial growth rate spectra with measured wave spectra shows that there is excellent qualitative agreement between the linear theory and the observed wave characteristics.« less

Direct multiple path magnetospheric propagation - A fundamental property of nonducted VLF waves

NASA Technical Reports Server (NTRS)

Sonwalkar, V. S.; Bell, T. F.; Helliwell, R. A.; Inan, U. S.

1984-01-01

An elongation of 20-200 ms, attributed to closely spaced multiple propagation paths between the satellite and the ground, is noted in well defined pulses observed by the ISEE 1 satellite in nonducted whistler mode signals from the Siple Station VLF transmitter. Electric field measurements show a 2 to 10 dB amplitude variation in the observed amplitude fading pattern which is also consistent with direct multiple path propagation. The results obtained for two cases, one outside and one inside the plasmapause, establish that the direct signals transmitted from the ground arrive almost simultaneously at any point in the magnetosphere along two or more closely spaced direct ray paths. It is also shown that multiple paths can be explained by assuming field-aligned irregularities, and the implications of these results for nonducted wave-particle interaction in the magnetosphere are discussed. For reasonable parameters of nonducted, multiple path propagation, a cyclotron-resonant electron will experience a wave Doppler broadening of a few tens to a few hundreds of Hz.

The turbulent plasmasphere boundary layer and the outer radiation belt boundary

NASA Astrophysics Data System (ADS)

Mishin, Evgeny; Sotnikov, Vladimir

2017-12-01

We report on observations of enhanced plasma turbulence and hot particle distributions in the plasmasphere boundary layer formed by reconnection-injected hot plasma jets entering the plasmasphere. The data confirm that the electron pressure peak is formed just outward of the plasmapause in the premidnight sector. Free energy for plasma wave excitation comes from diamagnetic ion currents near the inner edge of the boundary layer due to the ion pressure gradient, electron diamagnetic currents in the entry layer near the electron plasma sheet boundary, and anisotropic (sometimes ring-like) ion distributions revealed inside, and further inward of, the inner boundary. We also show that nonlinear parametric coupling between lower oblique resonance and fast magnetosonic waves significantly contributes to the VLF whistler wave spectrum in the plasmasphere boundary layer. These emissions represent a distinctive subset of substorm/storm-related VLF activity in the region devoid of substorm injected tens keV electrons and could be responsible for the alteration of the outer radiation belt boundary during (sub)storms.

Differential drift of plasma clouds in the magnetosphere: an update

NASA Astrophysics Data System (ADS)

Lemaire, J. F.

2001-07-01

First, Brice's (Journal of Geophysical Research 72 (1967) 5193) original theory for the formation of the plasmapause is recalled. Next, the motivation for writing a modification to this early theory is pointed out. The key aspects of Brice's manuscript are outlined and discussed. The mechanism of interchange driven by gravitational forces, centrifugal effects and kinetic pressure is considered in the cases when the integrated Pedersen conductivity is (i) negligibly small (as in Chandrasekhar's, Plasma Physics, University of Chicago Press, Chicago, 1960, 217 pp. and Longmire's, Elementary Plasma Physics, Wiley Interscience, New York, 1963, 296 pp., textbooks), (ii) infinitely large (as in many magnetospheric convection models), or (iii) has a finite value of the order of 0.2 mho, as in the Earth's ionosphere. Updates of this theory of interchange resulting from the existence of weak double layers, from quasi-interchange, or from the effects of an additional population of energetic ring-current particles forming the extended tail of the velocity distribution function, have also been reexamined.

The inner edge of the plasma sheet and the diffuse aurora

NASA Technical Reports Server (NTRS)

Fairfield, D. H.; Vinas, A. F.

1983-01-01

Three dimensional measurements from the ISEE-1 low energy electron spectrometer are used to map the location of the inner edge of the plasma sheet and study the anisotropies in the electron distribution function associated with this boundary. Lower energy plasma sheet electrons have inner edges closer to the Earth than higher energies with the separations at different energies being larger near dawn and after dusk than at midnight. Lowest energy inner edges are frequently located adjacent to the plasmapause in the dawn hemisphere but are often separated from it in the dusk hemisphere by a gap of at least several Re. The energy dispersion is minimal in the afternoon quadrant where the inner edge is near the magnetopause and frequently oscillating on a time scale of minutes. The location of the inner edge is probably determined primarily by the motion of electrons in the existing electric and magnetic fields rather than by strong diffusion as has sometimes been supposed.

Unique concurrent observations of whistler mode hiss, chorus, and triggered emissions

NASA Astrophysics Data System (ADS)

Hosseini, Poorya; Gołkowski, Mark; Turner, Drew L.

2017-06-01

We present a unique 2 h ground-based observation of concurrent magnetospheric hiss, chorus, VLF triggered emissions as well as ELF/VLF signals generated locally by the High Frequency Active Auroral Research Program (HAARP) facility. Eccentricity of observed wave polarization is used as a criteria to identify magnetospheric emissions and estimate their ionospheric exit points. The observations of hiss and chorus in the unique background of coherent HAARP ELF/VLF waves and triggered emissions allow for more accurate characterization of hiss and chorus properties than in typical ground-based observations. Eccentricity and azimuth results suggest a moving ionospheric exit point associated with a single ducted path at L 5. The emissions exhibit dynamics in time suggesting an evolution of a magnetospheric source from hiss generation to chorus generation or a moving plasmapause location. We introduce a frequency band-limited autocorrelation method to quantify the relative coherency of the emissions. A range of coherency was observed from high order of coherency in local HAARP transmissions and their echoes to lower coherency in natural chorus and hiss emissions.

A storm-time plasmasphere evolution study using data assimilation

NASA Astrophysics Data System (ADS)

Nikoukar, R.; Bust, G. S.; Bishop, R. L.; Coster, A. J.; Lemon, C.; Turner, D. L.; Roeder, J. L.

2017-12-01

In this work, we study the evolution of the Earth's plasmasphere during geomagnetic active periods using the Plasmasphere Data Assimilation (PDA) model. The total electron content (TEC) measurements from an extensive network of global ground-based GPS receivers as well as GPS receivers on-board Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites and Communications/Navigation Outage Forecasting System (C/NOFS) satellite are ingested into the model. Global Core Plasma model, which is an empirical plasmasphere model, is utilized as the background model. Based on the 3D-VAR optimization, the PDA assimilative model benefits from incorporation of regularization techniques to prevent non-physical altitudinal variation in density estimates due to the limited-angle observational geometry. This work focuses on the plasmapause location, plasmasphere erosion time scales and refilling rates during the main and recovery phases of geomagnetic storms as estimated from the PDA 3-dimensional global maps of electron density in the ionosphere/plasmasphere. The comparison between the PDA results with in-situ density measurements from THEMIS and Van Allen Probes, and the RCM-E first-principle model will be also presented.

Effects of convection electric field on the distribution of ring current type protons

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.; Chen, A. J.

1975-01-01

The topology of the boundaries of penetration (or, inversely, the boundaries of the forbidden regions) of 90-deg pitch-angle equatorial protons with energies less than 100 keV are explored for an equatorial convection E-field which is directed in general from dawn to dusk. Due to the dependence of drift path on energy (or magnetic moment), complex structural features are expected in the proton energy spectra detected by satellites since the penetration distance of a proton is not a monotonically increasing or decreasing function of energy. During a storm when the convection E is enhanced, model calculations predict elongations of the forbidden regions analogous to tail extensions of the plasmasphere. Following a reduction in the convection field, spiral-structured forbidden regions can occur. Structural features inherent to large-scale convection field changes may be seen in the nose-like proton spectrograms observed near dusk by instrumentation on Explorer 45. These nose events are modelled by using an electric field model developed originally by Volland (1973). The strength of the field is related to the Kp index through night-time equatorial plasmapause measurements.

Spatial and Temporal Response of Auroral and Subauroral Plasma Convection to High- Latitude Drivers of Geomagnetic Activity

NASA Astrophysics Data System (ADS)

Greenwald, R. A.; Ruohoniemi, M.; Baker, J. B.; Talaat, E.; Lester, M.; Oksavik, K.

2008-12-01

During the IPY, the second of two lower-latitude SuperDARN radars was put into operation in the eastern U.S. Located at Blackstone, VA and directed toward central Canada, it extends the coverage of the preexisting Wallops Island radar to more than 4 hours of magnetic local time and covers 50-70 degrees geomagnetic latitude providing coverage of ionospheric plasma convection and electric fields on magnetic field lines connected to the inner boundary of the plasmasheet, ring current and plasmapause. Although initial measurements with this coordinated pair of radars were made at a time of low geomagnetic activity, there have been many opportunities to examine both the spatial and temporal response of low-latitude auroral and subauroral plasma convection and its associated electric field to a variety of high-latitude magnetospheric drivers including dayside reconnection and midnight sector substorms. In this paper, we discuss the dynamical response of these flows to both dayside reconnection and substorms. We specifically examine the timing, location, spatial extent and intensity of these flow enhancements versus the nature and strength of the driver.

Plasmasphere dynamics in the duskside bulge region: A new look at old topic

NASA Technical Reports Server (NTRS)

Carpenter, D. L.; Giles, B. L.; Chappell, C. R.; Decreau, P. M. E.; Anderson, R. R.; Persoon, A. M.; Smith, A. J.; Corcuff, Y.; Canu, P.

1993-01-01

Data acquired during several multiday periods in 1982 at ground stations Siple, Halley, and Kerguelen and on satellites Dynamics Explorer 1, International Sun Earth Explorer 1, and GEOS 2 have been used to investigate thermal plasma structure and dynamics in the duskside plasmasphere bulge region of the Earth. The distribution of thermal plasma in the dusk bulge sector is difficult to describe realistically, in part because of the time integral manner in which the thermal plasma distribution depends upon on the effects of bulk cross-B flow and interchange plasma flows along B. While relatively simple MHD models can be useful for qualitatively predicting certain effects of enhanced convection on a quiet plasmasphere, such as an initial sunward entrainment of the outer regions, they are of limited value in predicting the duskside thermal plasma structures that are observed. Furthermore, use of such models can be misleading if one fails to realize that they do not address the question of the formation of the steep plasmapause profile or provide for a possible role of instabilities or other irreversible processes in plasmapause formation. Our specific findings, which are based both upon the present case studies and upon earlier work, include the following: (1) during active periods the plasmasphere appears to become divided into two entities, a main plasmasphere and a duskside bulge region. (2) in the aftermath of an increase in convection activity, the main plasmasphere tends (from a statistical point of view) to become roughly circular in equatorial cross section, with only a slight bulge at dusk; (3) the abrupt westward edge of the duskside bulge observed from whistlers represents a state in the evolution of sunward extending streamers; (4) in the aftermath of a weak magnetic storm, 10 to 30% of the plasma 'removed' from the outer plasmasphere appears to remain in the afternoon-dusk sector beyond the main plasmasphere. (5) outlying dense plasma structures may circulate in the outer duskside magetosphere for many days following an increase in convection, unless there is extremely deep quieting; (6) a day-night plasmatrough boundary may be identified in equatorial satellite data; (7) factor-of-2-to-10 density irregularities appear near the plasmatrough from the ionosphere at L = 4.6, predominantly bidirectional field aligned and equatorially trapped light ion pitch angle distributions give away to a predominantly isotropic distribution (as seen by DE 1) when the plasma density reaches a level a factor of about 3 below the satured plasmasphere level; (9) some outlying dense plasma structures are effectively detached from the main plasmasphere, while others appear to be connected to that body.

Are Ring Current Ions Lost in Electromagnetic Ion Cyclotron Wave Dispersion Relation?

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.

2006-01-01

Electromagnetic ion cyclotron (EMIC) waves are widely observed in the inner and outer magnetosphere, at geostationary orbit, at high latitudes along the plasmapause, and at the ionospheric altitudes. Interaction of the Ring Current (RC) ions and EMIC waves causes ion scattering into the loss cone and leads to decay of the RC, especially during the main phase of storms when the RC decay times of about one hour or less are observed. The oblique EMIC waves damp due to Landau resonance with the thermal plasmaspheric electrons, and subsequent transport of the dissipating wave energy into the ionosphere below causes an ionosphere temperature enhancement. Induced scattering of these waves by the plasmaspheric thermal ions leads to ion temperature enhancement, and forms a so-called hot zone near the plasmapause where the temperature of core plasma ions can reach tens of thousands of degrees. Relativistic electrons in the outer radiation belt also interact well with the EMIC waves, and during the main and/or recovery phases of the storms these electrons can easily be scattered into the loss cone over a time scale from several hours to a day. The plasma density distribution in the magnetosphere and the ion content play a critical role in EMIC wave generation and propagation, but the wave dispersion relation in the known RC-EMIC wave interaction models is assumed to be determined by the thermal plasma distribution only. In these models, the modification of the EMIC wave dispersion relation caused by the RC ions is not taken into account, and the RC ions are only treated as a source of free energy in order to generate EMIC waves. At the same time, the RC ions can dominate the thermal magnetospheric content in the night MLT sector at great L shells during the main and/or recovery storm phase. In this study, using our self-consistent RC-EMIC wave model [Khazanov et al., 2006], we simulate the May 1998 storm in order to quantify the global EMIC wave redistribution caused by taking into account the RC ions in the EMIC wave dispersion relation. The dramatic wave pattern redistribution is observed in the postdusk-predawn MLT sector (night sector) for L greater than 5. We found the intense EMIC waves (about a few nT) there during the main and early recovery phases of the storm. The observed wave generation in this sector is caused by taking into account the EMIC wave dispersion change due to the RC ions. There are no waves at these locations in our model if the RC ions are taken into account in the wave growth rate only, and the wave dispersion relation is only governed by the thermal plasmaspheric model.

Effect of Ring Current Ions on Electromagnetic Ion Cyclotron Wave Dispersion Relation

NASA Technical Reports Server (NTRS)

Gamayunov, K. V.; Khazanov, G. V.

2006-01-01

Electromagnetic ion cyclotron (EMIC) waves are widely observed in the inner and outer magnetosphere, at geostationary orbit, at high latitudes along the plasmapause, and at the ionospheric altitudes. Interaction of the Ring Current (RC) ions and EMIC waves causes ion scattering into the loss cone and leads to decay of the RC, especially during the main phase of storms when the RC decay times of about one hour or less are observed. The oblique EMIC waves damp due to Landau resonance with the thermal plasmaspheric electrons, and subsequent transport of the dissipating wave energy into the ionosphere below causes an ionosphere temperature enhancement. Induced scattering of these waves by the plasmaspheric thermal ions leads to ion temperature enhancement, and forms a so-called hot zone near the plasmapause where the temperature of core plasma ions can reach tens of thousands of degrees. Relativistic electrons in the outer radiation belt also interact well with the EMIC waves, and during the main and/or recovery phases of the storms these electrons can easily be scattered into the loss cone over a time scale from several hours to a day. The plasma density distribution in the magnetosphere and the ion content play a critical role in EMIC wave generation and propagation, but the wave dispersion relation in the known RC-EMIC wave interaction models is assumed to be determined by the thermal plasma distribution only. In these models, the modification of the EMIC wave dispersion relation caused by the RC ions is not taken into account, and the RC ions are only treated as a source of free energy in order to generate EMIC waves. At the same time, the RC ions can dominate the thermal magnetospheric content in the night MLT sector at great L shells during the main and/or recovery storm phase. In this study, using our self-consistent RC-EMIC wave model [Khazanov et al., 2006], we simulate the May 1998 storm in order to quantify the global EMIC wave redistribution caused by taking into account the RC ions in the EMIC wave dispersion relation. The dramatic wave pattern redistribution is observed in the postdusk-predawn MLT sector (night sector) for L greater than 5. We found the intense EMIC waves (about a few nT) there during the main and early recovery phases of the storm. The observed wave generation in this sector is caused by taking into account the EMIC wave dispersion change due to the RC ions. There are no waves at these locations in our model if the RC ions are taken into account in the wave growth rate only, and the wave dispersion relation is only governed by the thermal plasmaspheric model.

Roles of hot electrons in generating upper-hybrid waves in the earth's radiation belt

DOE PAGES

Hwang, J.; Shin, D. K.; Yoon, P. H.; ...

2017-05-01

Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth's radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such fluctuations has not been discussed in detail. The present paper carries out detailed analyses of data from the Waves instrument, which is part of the Electric and Magneticmore » Field Instrument Suite and Integrated Science suite onboard the Van Allen Probes. Combined with the theoretical calculation, it is shown that the peak intensity associated with the upper-hybrid fluctuations might be predominantly determined by tenuous but hot electrons and that denser cold background electrons do not seem to contribute much to the peak intensity. This finding shows that upper-hybrid fluctuations detected during quiet time are not only useful for the determination of the background cold electron density but also contain information on the ambient hot electrons population as well.« less

On the Azimuthal Variation of Core Plasma in the Equatorial Magnetosphere

NASA Technical Reports Server (NTRS)

Gallagher, D. L.; Craven, P. D.; Comfort, R. H.; Moore, T. E.

1995-01-01

Previous results of plasmapause position surveys have been synthesized into a description of the underlying global distribution of plasmasphere-like or core plasma densities unique to a steady state magnetosphere. Under these steady conditions, the boundary between high- and low-density regions is taken to represent the boundary between diurnal near-corotation and large-scale circulation streamlines that traverse the entire magnetosphere. Results indicate a boundary that has a pronounced bulge in the dusk sector that is rotated westward and markedly reduced in size at increased levels of geomagnetic activity (and presumably magnetospheric convection). The derived profile is empirical confirmation of an underlying 'tear drop' distribution of core plasma, which is valid only for prolonged steady conditions and is somewhat different from that associated with the simple superposition of sunward flow and corotation, both in its detailed shape and in its varying orientation. Variation away from the tear drop profile suggests that magnetospheric circulation departs from a uniform flow field, having a radial dependence with respect to the Earth that is qualitatively consistent with electrostatic shielding of the convection electric field and which is rotated westward at increased levels of geophysical activity.

Diffusive vs. impulsive energetic electron transport during radiation belt storms

NASA Astrophysics Data System (ADS)

Vassiliadis, D.; Koepke, M.; Tornquist, M.

2008-12-01

Earth's electron radiation belts are continually replenished by inward particle transport (as well as other, local acceleration processes) taking place during radiation belt storms. For some storms the radial transport is primarily diffusive while for others it is impulsive, or characterized by injections. To distinguish between these types of inward transport, we first use a dynamic model of the phase-space density as measured by POLAR/HIST and expressed in terms of adiabatic invariants [Green and Kivelson, 2004]. In a review of storms from 1997 to 2004 the coefficients of the model are peaked at characteristic temporal and phase- space (mu, k, L*) scales during specific storms. The transport is quantified in terms of those invariants which are violated and identified with peaks of the electron distribution in invariant space. Second, we run guiding- center simulations in wave fields fitted to in situ measurements complemented at low and high L by ground ULF pulsations. The modes of response identified in earlier studies from SAMPEX and POLAR electron flux measurements are now associated with primarily diffusive transport in the central range of the outer belt, L=4-8, and primarily impulsive transport near the plasmapause boundary, L=3-4.

The role of cold plasma and its composition on the growth of electromagnetic ion cyclotron waves in the inner magnetosphere

NASA Astrophysics Data System (ADS)

Snelling, J. M.; Johnson, J.; Engebretson, M. J.; Kim, E. H.; Tian, S.

2017-12-01

While it is currently well accepted that the free energy for growth of electromagnetic ion cyclotron (EMIC) waves in Earth's magnetosphere comes from unstable configurations of hot anisotropic ions that are injected into the ring current, several questions remain about what controls the instability. A recent study of the occurrence of EMIC waves relative to the plasmapause in Vallen Probes Data showed that plasma density gradients or enhancements were not the dominant factor in determining the site of EMIC wave generation [Tetrick et al. 2017]. However, the factors that control wave growth on each of the branches are not fully understood. For example, in some cases, the measured anisotropy is not adequate to explain local instability, and the relative importance of the density and composition of a cold plasma population is still uncertain. Several intervals of EMIC wave activity are analyzed to determine the role of a cold population in driving instability on each of the wave branches. This study utilizes the WHAMP (Waves in Homogeneous Anisotropic Magnetized Plasma) stability code with plasma distributions optimized to fit the observed distributions including temperature anisotropy, loss cone, and ring beam populations.

Cluster observations and simulations of He+ EMIC triggered emissions

NASA Astrophysics Data System (ADS)

Grison, B.; Shoji, M.; Santolik, O.; Omura, Y.

2012-12-01

EMIC triggered emissions have been reported in the inner magnetosphere at the edge of the plasmapause nightside [Pickett et al., 2010]. The generation mechanism proposed by Omura et al. [2010] is very similar to the one of the whistler chorus emissions and simulation results agree with observations and theory [Shoji et Omura, 2011]. The main characteristics of these emissions generated in the magnetic equatorial plane region are a frequency with time dispersion and a high level of coherence. The start frequency of previously mentioned observations is above half of the proton gyrofrequency. It means that the emissions are generated on the proton branch. On the He+ branch, generation of triggered emissions, in the same region, requests more energetic protons and the triggering process starts below the He+ gyrofrequency. It makes their identification in Cluster data rather difficult. Recent simulation results confirm the possibility of EMIC triggered emission on the He+ branch. In the present contribution we propose to compare a Cluster event to simulation results in order to investigate the possibility to identify observations to a He+ triggered emission. The impact of the observed waves on particle precipitation is also investigated.

Plasmaspheric Plumes Observed by the CLUSTER and IMAGE Spacecraft

NASA Technical Reports Server (NTRS)

Fung, S. F.; Benson, R. F.; Garcia, L. N.; Adrian, M. L.; Sandel, B.; Goldstein, M. L.

2008-01-01

Global IMAGE/EUV observations have revealed complex changes in plasmaspheric structures as the plasmasphere responds to geomagnetic activity while remaining under varying degrees of influence by co-rotation, depending on the radial distance. The complex plasmaspheric dynamics, with different scales of variability, is clearly far from being well understood. There is now renewed interest in the plasmasphere due to its apparent connections with the development of the ring current and radiation belt, and loss of ionospheric plasmas. Early in the mission, the Cluster spacecraft only crossed the plasmapause (L - 4) occasionally and made measurements of the outer plasmasphere and plasmaspheric drainage plumes. The study by Darrouzet et al. [2006] provided detailed analyses of in situ Cluster observations and IMAGE EUV observations of three plasmaspheric plumes detected in April-June, 2002. Within the next couple of years, Cluster orbit will change, causing perigee to migrate to lower altitudes, and thus providing excellent opportunities to obtain more detailed measurements of the plasmasphere. In this paper, we report our analyses of the earlier Cluster-IMAGE events by incorporating the different perspectives provided by the IMAGE Radio Plasma Imager (RPI) observations. We will discuss our new understanding of the structure and dynamics of the Cluster-IMAGE events.

Roles of hot electrons in generating upper-hybrid waves in the earth's radiation belt

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

Hwang, J.; Shin, D. K.; Yoon, P. H.

Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth's radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such fluctuations has not been discussed in detail. The present paper carries out detailed analyses of data from the Waves instrument, which is part of the Electric and Magneticmore » Field Instrument Suite and Integrated Science suite onboard the Van Allen Probes. Combined with the theoretical calculation, it is shown that the peak intensity associated with the upper-hybrid fluctuations might be predominantly determined by tenuous but hot electrons and that denser cold background electrons do not seem to contribute much to the peak intensity. This finding shows that upper-hybrid fluctuations detected during quiet time are not only useful for the determination of the background cold electron density but also contain information on the ambient hot electrons population as well.« less

Motions of charged particles in the magnetosphere under the influence of a time-varying large scale convection electric field

NASA Technical Reports Server (NTRS)

Smith, P. H.; Hoffman, R. A.; Bewtra, N. K.

1979-01-01

The motions of charged particles under the influence of the geomagnetic and electric fields are quite complex in the region of the inner magnetosphere. The Volland-Stern type large-scale convection electric field with gamma = 2 has been used successfully to predict both the plasmapause location and particle enhancements determined from Explorer 45 (S3-A) measurements. Recently introduced into the trajectory calculations of Ejiri et al. (1978) is a time dependence in this electric field based on the variation in Kp for actual magnetic storm conditions. The particle trajectories are computed as they change in this time-varying electric field. Several storm fronts of particles of different magnetic moments are allowed to be injected into the inner magnetosphere from L = 10 in the equatorial plane. The motions of these fronts are presented in a movie format. The local time of injection, the particle magnetic moments and the subsequent temporal history of the magnetospheric electric field play important roles in determining whether the injected particles are trapped within the ring current region or whether they are convected to regions outside the inner magnetosphere.

Wave and plasma observations during a compressional Pc 5 wave event August 10, 1982

NASA Technical Reports Server (NTRS)

Engebretson, M. J.; Cahill, L. J., Jr.; Waite, J. H., Jr.; Gallagher, D. L.; Chandler, M. O.; Sugiura, M.

1986-01-01

Magnetometer and thermal plasma instruments on the polar-orbiting Dynamics Explorer 1 satellite observed a small-amplitude ultralow frequency pulsation event at the outer edge of the plasmapause near the geomagnetic equator in the midafternoon sector on August 10, 1982, during the recovery phase of a magnetic storm. Transverse pulsations of 30-50 s period were observed throughout the event, and a 270-s period, purely compressional Pc 5 pulsation with several shifts in phase occurred within + or - 5 deg of the geomagnetic equator. Electric fields and the motion of thermal ions appeared to be in quadrature with pulsations in magnetic field magnitude throughout the event. This suggests that the net Poynting flux for the compressional waves was zero, consistent with their being standing waves. Large fluxes of trapped 90 deg pitch angle 10-eV protons, also symmetric about the geomagnetic equator, were observed in conjunction with the waves. These may serve as a source of free energy for the pulsations. These observations lend support to recent studies suggesting that many dayside compressional wave events are related to localized field line resonance near plasmapauselike boundaries, but also include features that cannot be explained by existing theories.

Wave and plasma observations during a compressional Pc 5 wave event August 10, 1982

NASA Astrophysics Data System (ADS)

Engebretson, M. J.; Cahill, L. J., Jr.; Waite, J. H., Jr.; Gallagher, D. L.; Chandler, M. O.; Sugiura, M.; Weimer, D. R.

1986-06-01

Magnetometer and thermal plasma instruments on the polar-orbiting Dynamics Explorer 1 satellite observed a small-amplitude ultralow frequency pulsation event at the outer edge of the plasmapause near the geomagnetic equator in the midafternoon sector on August 10, 1982, during the recovery phase of a magnetic storm. Transverse pulsations of 30-50 s period were observed throughout the event, and a 270-s period, purely compressional Pc 5 pulsation with several shifts in phase occurred within + or - 5 deg of the geomagnetic equator. Electric fields and the motion of thermal ions appeared to be in quadrature with pulsations in magnetic field magnitude throughout the event. This suggests that the net Poynting flux for the compressional waves was zero, consistent with their being standing waves. Large fluxes of trapped 90 deg pitch angle 10-eV protons, also symmetric about the geomagnetic equator, were observed in conjunction with the waves. These may serve as a source of free energy for the pulsations. These observations lend support to recent studies suggesting that many dayside compressional wave events are related to localized field line resonance near plasmapauselike boundaries, but also include features that cannot be explained by existing theories.

Distinguishing Among Mechanisms That Determine Pi 2 Pulsation Period

NASA Astrophysics Data System (ADS)

Takahashi, K.; Lysak, R. L.; Hartinger, M.; Kletzing, C.; Smith, C. W.; Singer, H. J.

2017-12-01

Pi2 pulsations are an integral component of substorms, with their association with magnetic field dipolarization, particle injection, auroral brightening, and intensification of field-aligned currents. An important question about Pi2 pulsations is how their periodicity is established. Two possible mechanisms are forcing of the inner magnetosphere by periodic variations of the near-Earth plasma bulk flows, and the cavity mode response of the plasmasphere to impulsive or irregular disturbances propagating from the tail. We address this question using observations of four Pi2 pulsations that occurred in a 2-hour time span on 29 July 2013. These events were observed by THEMIS, Van Allen Probes (RBSP), and geostationary GOES and ETS-VIII, while some of these spacecraft were nearly radially aligned in the evening sector at radial distances between 2 and 10 Earth radii. Electron density data are available from THEMIS and RBSP to determine the spacecraft location relative to the plasmapause. We examine the time delay of oscillations among the spacecraft and the local wave properties such as polarization and phase delay between the electric and magnetic field components. We compare the observations with ULF wave simulations in a dipole magnetosphere to evaluate which of the two possible Pi2 generation mechanisms was more effective.

Overview of Emic Triggered Chorus Emissions in Cluster Data

NASA Astrophysics Data System (ADS)

Grison, B.; Pickett, J. S.; Omura, Y.; Santolik, O.; Engebretson, M. J.; Dandouras, I. S.; Masson, A.; Decreau, P. M.; Adrian, M. L.; Cornilleau Wehrlin, N.

2010-12-01

Electromagnetic ion cyclotron (EMIC) triggered emissions have been recently observed onboard the Cluster spacecraft close to the plasmapause in the equatorial region of the magnetosphere (Pickett et al., 2010). The nonlinear mechanism of the wave amplification is the same as for the well known whistler-mode chorus emissions (Omura et al., 2010). The EMIC triggered emissions appear as risers: electromagnetic structures that have a positive frequency drift with time. They can thus be considered as the EMIC analogue of rising frequency whistler-mode chorus emissions. In addition, they propagate away from the magnetic equator. These EMIC risers are not common in Cluster data. We present an overview of the properties of all the identified cases. Risers can be sorted out in two groups: in the first one the starting frequency of EMIC emissions is close to one half of the local proton gyrofrequency and the risers have a clear left-hand polarization. In the second group the risers have an opposite polarization with a starting frequency close to one half of the He+ gyrofrequency. Most of the cases have been detected close to 22 MLT (magnetic local time). This dependence will be investigated to determine if it is linked to the orbit effects or if there is a physical cause.

The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

NASA Astrophysics Data System (ADS)

Lei, Mingda; Xie, Lun; Li, Jinxing; Pu, Zuyin; Fu, Suiyan; Ni, Binbin; Hua, Man; Chen, Lunjin; Li, Wen

2017-12-01

Magnetosonic (MS) waves have been found capable of creating radiation belt electron butterfly distributions in the inner magnetosphere. To investigate the physical nature of the interactions between radiation belt electrons and MS waves, and to explore a preferential condition for MS waves to scatter electrons efficiently, we performed a comprehensive parametric study of MS wave-electron interactions using test particle simulations. The diffusion coefficients simulated by varying the MS wave frequency show that the scattering effect of MS waves is frequency insensitive at low harmonics (f < 20 fcp), which has great implications on modeling the electron scattering caused by MS waves with harmonic structures. The electron scattering caused by MS waves is very sensitive to wave normal angles, and MS waves with off 90° wave normal angles scatter electrons more efficiently. By simulating the diffusion coefficients and the electron phase space density evolution at different L shells under different plasma environment circumstances, we find that MS waves can readily produce electron butterfly distributions in the inner part of the plasmasphere where the ratio of electron plasma-to-gyrofrequency (fpe/fce) is large, while they may essentially form a two-peak distribution outside the plasmapause and in the inner radiation belt where fpe/fce is small.

Nonlinear Scattering of VLF Waves in the Radiation Belts

NASA Astrophysics Data System (ADS)

Crabtree, Chris; Rudakov, Leonid; Ganguli, Guru; Mithaiwala, Manish

2014-10-01

Electromagnetic VLF waves, such as whistler mode waves, control the lifetime of trapped electrons in the radiation belts by pitch-angle scattering. Since the pitch-angle scattering rate is a strong function of the wave properties, a solid understanding of VLF wave sources and propagation in the magnetosphere is critical to accurately calculate electron lifetimes. Nonlinear scattering (Nonlinear Landau Damping) is a mechanism that can strongly alter VLF wave propagation [Ganguli et al. 2010], primarily by altering the direction of propagation, and has not been accounted for in previous models of radiation belt dynamics. Laboratory results have confirmed the dramatic change in propagation direction when the pump wave has sufficient amplitude to exceed the nonlinear threshold [Tejero et al. 2014]. Recent results show that the threshold for nonlinear scattering can often be met by naturally occurring VLF waves in the magnetosphere, with wave magnetic fields of the order of 50-100 pT inside the plasmapause. Nonlinear scattering can then dramatically alter the macroscopic dynamics of waves in the radiation belts leading to the formation of a long-lasting wave-cavity [Crabtree et al. 2012] and, when amplification is present, a multi-pass amplifier [Ganguli et al. 2012]. By considering these effects, the lifetimes of electrons can be dramatically reduced. This work is supported by the Naval Research Laboratory base program.

Venus: mass, gravity field, atmosphere, and ionosphere as measured by the mariner 10 dual-frequency radio system.

PubMed

Howard, H T; Tyler, G L; Fjeldbo, G; Kliore, A J; Levy, G S; Brunn, D L; Dickinson, R; Edelson, R E; Martin, W L; Postal, R B; Seidel, B; Sesplaukis, T T; Shirley, D L; Stelzried, C T; Sweetnam, D N; Zygielbaum, A I; Esposito, P B; Anderson, J D; Shapiro, I I; Reasenberg, R D

1974-03-29

Analysis of the Doppler tracking data near encounter yields a value for the ratio of the mass of the sun to that of Venus of 408,523.9 +/- 1.2, which is in good agreement with prior determinations based on data from Mariner 2 and Mariner 5. Preliminary analysis indicates that the magnitudes of the fractional differences in the principal moments of inertia of Venus are no larger than 10(-4), given that the effects of gravity-field harmonics higher than the second are negligible. Additional analysis is needed to determine the influence of the higher order harmonics on this bound. Four distinct temperature inversions exist at altitudes of 56, 58, 61, and 63 kilometers. The X-band signal was much more rapidly attenuated than the S-band signal and disappeared completely at 52-kilometer altitude. The nightside ionosphere consists of two layers having a peak density of 10(4) electrons per cubic centimeter at altitudes of 140 and 120 kilometers. The dayside ionosphere has a peak density of 3 X 10(5) electrons per cubic centimeter at an altitude of 145 kilometers. The electron number density observed at higher altitudes was ten times less than that observed by Mariner 5, and no strong evidence for a well-defined plasmapause was found.

Explorer 45 wave observations during the large magnetic storm of August 4-5, 1972

NASA Technical Reports Server (NTRS)

Taylor, W. W. L.; Anderson, R. G.

1977-01-01

The magnetospheric compression associated with the very large magnetic storm of August 4-5, 1972, provided an opportunity for Explorer 45 to observe plasma waves in the magnetosphere and the magnetosheath during extremely disturbed conditions. Electrostatic noise bursts were observed near the plasmapause in electric-field channels from 35 Hz to 5.62 kHz. In the outer magnetosphere, electric-field noise bands apparently harmonically related to the electron gyrofrequency with components as low as 3 kHz and as high as 50 kHz were observed. The electric field of the fundamental was perpendicular to the magnetic-field vector. A mechanism including the electron cyclotron instability may generate the noise band. Hiss of 100-1000 Hz was observed in the outer magnetosphere. The electromagnetic hiss was generally weak and was observed in the magnetic wide-band data only when it was strong. In the magnetosheath broad band, incoherent noise (hiss) was observed from 1 Hz to 100 kHz. This magnetosheath hiss was the strongest phenomenon observed by the plasma-wave detectors during the lifetime of Explorer 45. The highest intensities of magnetosheath hiss occurred at the magnetopause. Its broad-band nature suggests that magnetosheath hiss was generated locally. Broad-band noise bursts and short bursts of chorus were also observed in the magnetosheath.

Characterization of radiation belt electron energy spectra from CRRES observations

NASA Astrophysics Data System (ADS)

Johnston, W. R.; Lindstrom, C. D.; Ginet, G. P.

2010-12-01

Energetic electrons in the outer radiation belt and the slot region exhibit a wide variety of energy spectral forms, more so than radiation belt protons. We characterize the spatial and temporal dependence of these forms using observations from the CRRES satellite Medium Electron Sensor A (MEA) and High-Energy Electron Fluxmeter (HEEF) instruments, together covering an energy range 0.15-8 MeV. Spectra were classified with two independent methods, data clustering and curve-fitting analyses, in each case defining categories represented by power law, exponential, and bump-on-tail (BOT) or other complex shapes. Both methods yielded similar results, with BOT, exponential, and power law spectra respectively dominating in the slot region, outer belt, and regions just beyond the outer belt. The transition from exponential to power law spectra occurs at higher L for lower magnetic latitude. The location of the transition from exponential to BOT spectra is highly correlated with the location of the plasmapause. In the slot region during the days following storm events, electron spectra were observed to evolve from exponential to BOT yielding differential flux minima at 350-650 keV and maxima at 1.5-2 MeV; such evolution has been attributed to energy-dependent losses from scattering by whistler hiss.

Peaks in Phase Space Density: A Survey of the Van Allen Probes Era

NASA Astrophysics Data System (ADS)

Boyd, A. J.; Turner, D. L.; Reeves, G. D.; Spence, H. E.

2017-12-01

One of the challenges of radiation belt studies is the differentiation between acceleration mechanisms, particularly local acceleration and radial diffusion. This is often done through careful examination of phase space density profiles in terms of adiabatic coordinates. In particular, local acceleration processes produce growing peaks in phase space density. Many previous studies have shown clear observations of these features for individual events. However, it remains unclear how often and where these growing peaks are observed over a long time period. With the availability of several years of high quality observations from multiple spacecraft, we now have an opportunity to quantify phase space density profiles not only for multiple events, but also across a wide range of energies. In this study, we examine phase space density from more than four years of data from the Van Allen Probes and THEMIS to determine the statistical properties of the observed peaks in phase space density. First, we determine how often growing peaks are observed. Second, we examine where the peaks are located in terms of the adiabatic invariants mu, K and L* and how these locations relate to geomagnetic indices, solar wind conditions and the plasmapause location. Third, we explore how these peaks evolve in time. Together, these results will reveal the relative importance of different acceleration processes and how these affect the various electron populations within the radiation belt.

Long-lived plasmaspheric drainage plumes: Where does the plasma come from?

NASA Astrophysics Data System (ADS)

Borovsky, Joseph E.; Welling, Daniel T.; Thomsen, Michelle F.; Denton, Michael H.

2014-08-01

Long-lived (weeks) plasmaspheric drainage plumes are explored. The long-lived plumes occur during long-lived high-speed-stream-driven storms. Spacecraft in geosynchronous orbit see the plumes as dense plasmaspheric plasma advecting sunward toward the dayside magnetopause. The older plumes have the same densities and local time widths as younger plumes, and like younger plumes they are lumpy in density and they reside in a spatial gap in the electron plasma sheet (in sort of a drainage corridor). Magnetospheric-convection simulations indicate that drainage from a filled outer plasmasphere can only supply a plume for 1.5-2 days. The question arises for long-lived plumes (and for any plume older than about 2 days): Where is the plasma coming from? Three candidate sources appear promising: (1) substorm disruption of the nightside plasmasphere which may transport plasmaspheric plasma outward onto open drift orbits, (2) radial transport of plasmaspheric plasma in velocity-shear-driven instabilities near the duskside plasmapause, and (3) an anomalously high upflux of cold ionospheric protons from the tongue of ionization in the dayside ionosphere, which may directly supply ionospheric plasma into the plume. In the first two cases the plume is drainage of plasma from the magnetosphere; in the third case it is not. Where the plasma in long-lived plumes is coming from is a quandary: to fix this dilemma, further work and probably full-scale simulations are needed.

Conjugate Ground-Spacecraft Observations of VLF Chorus Elements

NASA Astrophysics Data System (ADS)

Demekhov, A. G.; Manninen, J.; Santolík, O.; Titova, E. E.

2017-12-01

We present results of simultaneous observations of VLF chorus elements at the ground-based station Kannuslehto in Northern Finland and on board Van Allen Probe A. Visual inspection and correlation analysis of the data reveal one-to-one correspondence of several (at least 12) chorus elements following each other in a sequence. Poynting flux calculated from electromagnetic fields measured by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probe A shows that the waves propagate at small angles to the geomagnetic field and oppositely to its direction, that is, from northern to southern geographic hemisphere. The spacecraft was located at L≃4.1 at a geomagnetic latitude of -12.4∘ close to the plasmapause and inside a localized density inhomogeneity with about 30% density increase and a transverse size of about 600 km. The time delay between the waves detected on the ground and on the spacecraft is about 1.3 s, with ground-based detection leading spacecraft detection. The measured time delay is consistent with the wave travel time of quasi-parallel whistler-mode waves for a realistic profile of the plasma density distribution along the field line. The results suggest that chorus discrete elements can preserve their spectral shape during a hop from the generation region to the ground followed by reflection from the ionosphere and return to the near-equatorial region.

Model of electron lifetimes inside the plasmasphere calculated using a CRRES derived hiss wave amplitude model

NASA Astrophysics Data System (ADS)

Orlova, Ksenia; Spasojevic, Maria; Shprits, Yuri

Particle populations in the inner magnetosphere can change by orders of magnitude on very short time scales. For the last decade observations and theoretical computations showed that resonant interaction of electrons with various plasma waves plays an important role in acceleration and loss mechanisms. Using data from the CRRES plasma wave experiment, we develop quadratic fits to the mean of the wave amplitude squared for plasmaspheric hiss as a function of geomagnetic activity (Kp) and magnetic latitude (lambda) for the dayside (6

A comparison of outer electron radiation belt dropouts during solar wind stream interface and magnetic cloud driven storms

NASA Astrophysics Data System (ADS)

Ogunjobi, O.; Sivakumar, V.; Mtumela, Z.

2017-06-01

Energetic electrons are trapped in the Earth's radiation belts which occupy a toroidal region between 3 and 7 \\hbox {R}E above the Earth's surface. Rapid loss of electrons from the radiation belts is known as dropouts. The source and loss mechanisms regulating the radiation belts population are not yet understood entirely, particularly during geomagnetic storm times. Nevertheless, the dominant loss mechanism may require an event based study to be better observed. Utilizing multiple data sources from the year 1997-2007, this study identifies radiation belt electron dropouts which are ultimately triggered when solar wind stream interfaces (SI) arrived at Earth, or when magnetic clouds (MC) arrived. Using superposed epoch analysis (SEA) technique, a synthesis of multiple observations is performed to reveal loss mechanism which might, perhaps, be a major contributor to radiation belt losses under SI and MC driven storms. Results show an abrupt slower decaying precipitation of electron peak (about 3000 counts/sec) on SI arrival within 5.05 < L < 6.05, which persist till 0.5 day before gradual recovery. This pattern is interpreted as an indication of depleted electrons from bounce lost cone via precipitating mechanism known as relativistic electron microburst. On the other hand, MC shows a pancake precipitating peak extending to lower L (Plasmapause); indicating a combination of electron cyclotron harmonic (ECH) and whistler mode waves as the contributing mechanisms.

Monitoring of the Spacecraft Potential in the Magetosphere With a Double Probe Instrument

NASA Astrophysics Data System (ADS)

Laakso, H.

1998-11-01

Measurements of the double probe instrument can be used for monitoring the variation of the spacecraft potential Vs in tenuous plasmas where the satellite usually floats at a positive potential. This study deals with the Vs variation of the Polar satellite in the magnetosphere, using three and half years of data in 1996-99. The observations are binned with the Kp index in order to investigate how the level of geomagnetic activity affects the average surface potential. Two different antenna baselines are used, 6 and 60 meters, which both can be used for monitoring the spacecraft potential. In a low-density environment, however, the short antenna measurements are more influenced by the charging sheath of the satellite, but the data are nevertheless qualitatively useful. In burst mode the sampling rate of the double probe experiment is 1-8 kHz, and then very fast spacecraft potential variations can be monitored. Typically Vs varies between 0 and 50 volts so that in the plasmasphere it is 0-1 volt, at the plasmapause it exhibits a steep increase by 3-5 volts, and outside the plasmasphere Vs is more than 5 volts. Highest Vs's occur in the high-altitude (> 4 RE) polar cap, where Vs is usually between 20 and 30 volts, and on auroral field lines where it frequently lies in the 30-50 volts range and occasionally above 50 volts.

The role of the large scale convection electric field in erosion of the plasmasphere during moderate and strong storms

NASA Astrophysics Data System (ADS)

Thaller, S. A.; Wygant, J. R.; Cattell, C. A.; Breneman, A. W.; Bonnell, J. W.; Kletzing, C.; De Pascuale, S.; Kurth, W. S.; Hospodarsky, G. B.; Bounds, S. R.

2015-12-01

The Van Allen Probes offer the first opportunity to investigate the response of the plasmasphere to the enhancement and penetration of the large scale duskward convection electric field in different magnetic local time (MLT) sectors. Using electric field measurements and estimates of the cold plasma density from the Van Allen Probes' Electric Fields and Waves (EFW) instrument, we study erosion of the plasmasphere during moderate and strong geomagnetic storms. We present the electric field and density data both on an orbit by orbit basis and synoptically, showing the behavior of the convection electric field and plasmasphere over a period of months. The data indicate that the large scale duskward electric field penetrates deep (L shell < 3) into the inner magnetosphere on both the dusk and dawn sides, but that the plasmasphere response on the dusk and dawn sides differ. In particular, significant (~2 orders of magnitude) decreases in the cold plasma density occur on the dawn side within hours of the onset of enhanced duskward electric field. In contrast, on the dusk side, the plasmapause is located at higher L shell than it is on the dawn side. In some cases, in the post-noon sector, cold plasma density enhancements accompany duskward electric field enhancements for the first orbit after the electric field enchantment, consistent with a duskside, sunward flowing, drainage plume.

EMIC triggered chorus emissions in Cluster data

NASA Astrophysics Data System (ADS)

Grison, B.; SantolíK, O.; Cornilleau-Wehrlin, N.; Masson, A.; Engebretson, M. J.; Pickett, J. S.; Omura, Y.; Robert, P.; Nomura, R.

2013-03-01

Electromagnetic ion cyclotron (EMIC) triggered chorus emissions have recently been a subject of several experimental, theoretical and simulation case studies, noting their similarities with whistler-mode chorus. We perform a survey of 8 years of Cluster data in order to increase the database of EMIC triggered emissions. The results of this is that EMIC triggered emissions have been unambiguously observed for only three different days. These three events are studied in detail. All cases have been observed at the plasmapause between 22 and 24 magnetic local time (MLT) and between - 15° and 15° magnetic latitude (λm). Triggered emissions are also observed for the first time below the local He+ gyrofrequency (fHe+). The number of events is too low to produce statistical results, nevertheless we point out a variety of common properties of those waves. The rising tones have a high level of coherence and the waves propagate away from the equatorial region. The propagation angle and degree of polarization are related to the distance from the equator, whereas the slope and the frequency extent vary from one event to the other. From the various spacecraft separations, we determine that the triggering process is a localized phenomenon in space and time. However, we are unable to determine the occurrence rates of these waves. Small frequency extent rising tones are more common than large ones. The newly reported EMIC triggered events are generally observed during periods of large AE index values and in time periods close to solar maximum.

SAID-SAPS Paradigm: Beliefs and Reality

NASA Astrophysics Data System (ADS)

Mishin, E. V.

2016-12-01

Enhanced westward flows are the dominant feature of the plasma convection in the perturbed subauroral geospace. These include latitudinally-narrow "polarization jets" (PJ) or "subauroral ion drifts" (SAID) observed mainly in the premidnight MLT sector and broad flow channels on the duskside. The generic term "sub-auroral polarization streams" (SAPS) was introduced to unite both (narrow and broad) flows, taking for granted that their underlying mechanisms are quite similar, if not the same. The concept of voltage and current generators is believed to explain the SAPS major features. The generator paradigm treats hot, ≥1 keV, plasma sheet (PS) particles as single (test) particles driven by the dawn-to-dusk and co-rotation electric fields and gradient-curvature drift disregarding charge neutrality and concomitant polarization fields, inherent in slow plasma processes. In this approach, the inner boundary of the hot ion trajectories on the duskside extends earthward of that of the PS electrons by some distance increasing toward dusk. However, magnetically conjugate observations in the evening sector reveal that the generator paradigm fails to explain the substorm SAID features and that they are rather explained in terms of a short-circuiting of substorm-injected hot plasma jets over the plasmapause. This report presents multispacecraft magnetically conjugate observations of substorm-enhanced flows on the duskside showing that their features are hardly compatible with the (test particle) generator paradigm. It is suggested that they are causally related to the two-loop system of the westward traveling surge.

A Model for Plasma Transport in a Corotation-Dominated Magnetosphere.

NASA Astrophysics Data System (ADS)

Pontius, Duane Henry, Jr.

1988-06-01

The gross structures of the magnetospheres of the outer planets are decided by processes quite different from those predominant in that of the earth. The terrestrial plasmapause, the boundary beyond which plasma motion is principally determined by magnetospheric interaction with the solar wind, is typically inside geosynchronous orbit. Within the plasmasphere, rotational effects are present, but gravity exceeds the centrifugal force of corotation. In contrast, the Jovian plasmasphere extends to a distance at least twenty times farther than synchronous orbit, affording a large region where rotational effects are expected to he clearly manifest (Brice and Ioannidis, 1970). The goal of this thesis is to develop an appropriate theoretical model for treating the problem of plasma transport in a corotation dominated plasmasphere. The model presented here is intended to describe the radial transport of relatively cold plasma having an azimuthally uniform distribution in a dipolar magnetic field. The approach is conceptually similar to that of the radial diffusion model in that small scale motions are examined to infer global consequences, but the physical understanding of those small scale motions is quite different. In particular, discrete flux tubes of small cross section are assumed to move over distances large compared to their widths. The present model also differs from the corotating convection model by introducing a mechanism whereby the conservation of flux tube content along flowlines is violated. However, it is quite possible that a global convection pattern co -exists with the motions described here, leading to longitudinal asymmetries in the plasma distribution.

Development of a methodology for deriving Plasmaspheric Total Electron Content from In-Situ electron density measurements in highly eccentric equatorial orbits

NASA Astrophysics Data System (ADS)

Sadhique, Aliyuthuman; Buckley, Andrew; Gough, Paul; Sussex Space Science Centre Team

2017-10-01

The contribution of the Upper Plasmasphere (defined as the altitudes above semi-synchronous orbit height to the Plasmapause height) to the TEC has been and continues to be un-quantified. The PEACE instrument in the Chinese - ESA Double Star TC1 satellite, the mission's orbit's high eccentricity, low perigee, high apogee and the resulting smaller incident angle while in the above altitude range provide the ideal geometric opportunity to build a methodology and to utilize its empirical in-situ electron density measurements to determine the Upper Plasmaspheric TEC component. Furthermore, the variation of the Inclination Angle of TC1 makes it a suitable equatorial mission confined to the Near-Equatorial region, ie 200 - 250 on either sides of the magnetic equator. As the most pronounced absolute TEC values and variations are within this region, it offers an excellent opportunity to build a Upper Plasmaspheric TEC database. This research generates such, first-ever database along its orbital path, using a methodology of approximation equating arcs of the orbits to straight-line TEC Bars, utilizing complex mathematics, also enabling the determination of the whole Plasmaspheric TEC from any eccentric orbital probe. Presented the paper in 15th International Workshop on Technical and Scientific Aspects of MST radar (MST15/iMST2)'' and ``18th EISCAT Symposium (EISCAT18)'' in Tokyo, Japan and The Royal Astronomical Society National Astronomy Meeting 2017.

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves

NASA Technical Reports Server (NTRS)

Kellogg, P. J.; Cattell, C. A.; Goetz, K.; Monson, S. J.; Wilson, L. B., III

2011-01-01

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 R(sub E) and 431 h inside 10 R(sub E) during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 m V/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48deg. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples/s, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes

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

Zhou, Qinghua; Xiao, Fuliang; Yang, Chang

The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. In this paper, we report simultaneous observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ~300–1500 Hz with themore » peak wave power density about 10 -5 nT 2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhile, hiss emissions are confined inside the plasmasphere, with a higher intensity and a broader area at a lower frequency. A sum of bi-Maxwellian distribution is used to model the observed anisotropic electron distributions and to evaluate the instability of waves. A three-dimensional ray tracing simulation shows that a portion of chorus emission outside the plasmasphere can propagate into the plasmasphere and evolve into plasmaspheric hiss. Moreover, hiss waves below 1 kHz are more intense and propagate over a broader area than those above 1 kHz, consistent with the observation. Finally, the current results can explain distributions of the observed hiss emission and provide a further support for the mechanism of evolution of chorus into hiss emissions.« less

Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes

DOE PAGES

Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; ...

2016-05-09

The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. In this paper, we report simultaneous observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ~300–1500 Hz with themore » peak wave power density about 10 -5 nT 2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhile, hiss emissions are confined inside the plasmasphere, with a higher intensity and a broader area at a lower frequency. A sum of bi-Maxwellian distribution is used to model the observed anisotropic electron distributions and to evaluate the instability of waves. A three-dimensional ray tracing simulation shows that a portion of chorus emission outside the plasmasphere can propagate into the plasmasphere and evolve into plasmaspheric hiss. Moreover, hiss waves below 1 kHz are more intense and propagate over a broader area than those above 1 kHz, consistent with the observation. Finally, the current results can explain distributions of the observed hiss emission and provide a further support for the mechanism of evolution of chorus into hiss emissions.« less

A UBK-space Visualization Tool for the Magnetosphere

NASA Astrophysics Data System (ADS)

Mohan, M.; Sheldon, R. B.

2001-12-01

One of the stumbling blocks to understanding particle transport in the magnetosphere has been the difficulty to follow, track and model the motion of ions through the realistic magnetic and electric fields of the Earth. Under the weak assumption that the first two invariants remain conserved, Whipple [1978] found a coordinate transformation that makes all charged particles travel on straight lines in UBK-space. The transform permits the quantitative calculation of conservative phase space transport for all particles with energies less than ~100 MeV, especially ring current energies (Sheldon and Gaffey [1993]). Furthermore Sheldon and Eastman [1997] showed how this transform extended the validity of diffusion models to realistic magnetospheres over the entire energy range. However, widespread usage of this transform has been limited by its non-intuitive UBK coordinates. We present a Virtual Reality Meta Language (VRML) interface to the calculation of UBK transform demonstrating its usefulness in describing both static features of the magnetosphere, such as the plasmapause, and dynamic features, such as ring current injection and loss. The core software is written in C for speed, whereas the interface is constructed in Perl and Javascript. The code is freely available, and intended for portability and modularity. R.B. Sheldon and T. Eastman ``Particle Transport in the Magnetosphere: A New Diffusion Model", GRL, 24(7), 811-814, 1997. Whipple, Jr, E. C. ``(U,B,K) coordinates: A natural system for studying magnetospheric convection". JGR, 83, 4318-4326, 1978. Sheldon, R. B. and J. D. Gaffey, Jr. ``Particle tracing in the magnetosphere: New algorithms and results." GRL, 20, 767-770, 1993.

Multi-instrument observations of the ionospheric and plasmaspheric density structure

NASA Astrophysics Data System (ADS)

Yizengaw, E.; Moldwin, M. B.

2008-05-01

: The density within the ionosphere and plasmasphere can be monitored using a combination of techniques that use both ground- and space-based instruments. We are combining diagnostic observations of everything, but the kitchen sink. These include observations of GPS TEC, TOPEX and JASON TEC, IMAGE EUV and FUV, GUVI composition data, ULF resonances, and many other multi-satellite data sets such as DMSP in situ observations. The dramatically growing number of GPS receivers on the ground and onboard Low-Earth-Orbit (LEO) satellites offers an excellent opportunity for remote sensing and monitoring of the ionospheric and plasmaspheric density structure using GPS TEC tomographic reconstruction technique. This allows us to clearly quantify magnetosphere-ionosphere (M-I) coupling dynamics, as well as confirm the long-standing conjecture that the mid-latitude trough and plasmapause are on the same field line. This has been demonstrated globally, for the first time, using a combination of data from IMAGE EUV and ground- and space-based GPS receivers. The two dimensional tomographic image of the ionosphere and plasmasphere, using data from the GPS receiver onboard LEO satellites, such as FedSat, CHAMP, COSMIC, etc, also provides a new ability to image the flux tube structure of ionospheric ion outflows, tracking flux tube structure up to 3.17Re (20,200 km) altitude for the first time. The combination of data from the altimeter on JASON and ground-based GPS network also provides an excellent opportunity to experimentally estimate the plasmaspheric density contribution to the ground-based GPS TEC and thus to the degradation of navigation and communication accuracy.

Propagation of EMIC triggered emissions toward the magnetic equatorial plane

NASA Astrophysics Data System (ADS)

Grison, B.; Santolik, O.; Pickett, J. S.; Omura, Y.; Engebretson, M. J.; Dandouras, I. S.; Masson, A.; Decreau, P.; Cornilleau-Wehrlin, N.

2011-12-01

EMIC triggered emissions are observed close to the equatorial plane of the magnetosphere at locations where EMIC waves are commonly observed: close to the plasmapause region and in the dayside magnetosphere close to the magnetopause. Their overall characteristics (frequency with time dispersion, generation mechanism) make those waves the EMIC analogue of rising frequency whistler-mode chorus emissions. In our observations the Poynting flux of these emissions is usually clearly arriving from the equatorial region direction, especially when observations take place at more than 5 degrees of magnetic latitude. Simulations have also confirmed that the conditions of generation by interaction with energetic ions are at a maximum at the magnetic equator (lowest value of the background magnetic field along the field line). However in the Cluster case study presented here the Poynting flux of EMIC triggered emissions is propagating toward the equatorial region. The large angle between the wave vector and the background magnetic field is also unusual for this kind of emission. The rising tone starts just above half of the He+ gyrofrequency (Fhe+) and it disappears close to Fhe+. At the time of detection, the spacecraft magnetic latitude is larger than 10 degrees and L shell is about 4. The propagation sense of the emissions has been established using two independent methods: 1) sense of the parallel component of the Poynting flux for a single spacecraft and 2) timing of the emission detections at each of the four Cluster spacecraft which were in a relatively close configuration. We propose here to discuss this unexpected result considering a reflection of this emission at higher latitude.

Variation Process of Radiation Belt Electron Fluxes due to Interaction With Chorus and EMIC Rising-tone Emissions Localized in Longitude

NASA Astrophysics Data System (ADS)

Kubota, Y.; Omura, Y.

2017-12-01

Using results of test particle simulations of a large number of electrons interacting with a pair of chorus emissions, we create Green's functions to model the electron distribution function after all of the possible interactions with the waves [Omura et al., 2015]. Assuming that the waves are generated in a localized range of longitudes in the dawn side, we repeat taking the convolution integral of the Green's function with the distribution function of the electrons injected into the generation region of the localized waves. From numerical and theoretical analyses, we find that electron acceleration process only takes place efficiently below 4 MeV. Because extremely relativistic electrons go through the wave generation region rapidly due to grad-B0 and curvature drift, they don't have enough interaction time to be accelerated. In setting up the electrons after all interaction with chorus emissions as initial electron distribution function, we also compute the loss process of radiation belt electron fluxes due to interaction with EMIC rising-tone emissions generated in a localized range of longitudes in the dusk side [Kubota and Omura,2017]. References: (1) Omura, Y., Y. Miyashita, M. Yoshikawa, D. Summers, M. Hikishima, Y. Ebihara, and Y. Kubota (2015), Formation process of relativistic electron flux through interaction with chorus emissions in the Earth's inner magnetosphere, J. Geophys. Res. Space Physics, 120, 9545-9562, doi:10.1002/2015JA021563. (2) Kubota, Y., and Y. Omura (2017), Rapid precipitation of radiation belt electrons induced by EMIC rising tone emissions localized in longitude inside and outside the plasmapause, J. Geophys. Res. Space Physics, 122, 293-309, doi:10.1002/2016JA023267.

Evolution of relativistic outer belt electrons during extended quiescent period

NASA Astrophysics Data System (ADS)

Jaynes, A. N.; Li, X.; Schiller, Q.; Blum, L. W.; Tu, W.; Malaspina, D.; Turner, D.; Baker, D. N.; Kanekal, S. G.; Blake, J. B.; Wygant, J. R.

2013-12-01

To effectively study loss due to precipitation of relativistic electron fluxes in the radiation belt, it is necessary to isolate this loss from the Dst effect and magnetopause shadowing by studying loss during a time of relatively quiet geomagnetic activity. We present a study of the slow decay of 200 keV - 2 MeV electron populations in the outer radiation belt during an extended quiescent period from ~15 Dec 2012 - 10 Jan 2013, wherein Dst never extended below -25 nT. We incorporate particle measurements from the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) onboard the Colorado Student Space Weather Experiment (CSSWE) CubeSat with measurements from the Relativistic Electron Proton Telescope (REPT) and the Magnetic Electron Ion Spectrometer (MagEIS) on the Van Allen Probes twin spacecraft to understand the evolution of the electron populations across pitch angle and energy. First, we present REPTile measurements of the precipitating populations (along with trapped & quasi-trapped) at a low-earth orbit, offering a view into the loss cone that is not as easily resolved using only the Van Allen Probes. Electron loss to the atmosphere during this event is quantified through use of a precipitation loss model, using the REPTile measurements. Additionally, phase space densities are derived using pitch-angle-resolved flux data from the REPT and MagEIS instruments, as well as from THEMIS SST data. Finally, we present the net loss effect on the outer radiation belt content during this time, by incorporating the modeled precipitation loss (from REPTile measurements) with Van Allen Probes electron flux data. Hiss and chorus wave data, along with approximate plasmapause location, from Van Allen Probes' Electric Field and Waves Suite (EFW) completes the picture by suggesting mechanisms for the precipitation loss of relativistic electrons during quiet time.

Effects of chorus, hiss and electromagnetic ion cyclotron waves on radiation belt dynamics (Invited)

NASA Astrophysics Data System (ADS)

Horne, R. B.

2013-12-01

Wave-particle interactions are known to play an important role in the acceleration and loss of radiation belt electrons, and in the heating and loss of ring current ions. The effectiveness of each wave type on radiation belt dynamics depends on the solar wind interaction with the magnetosphere and the properties of the waves which vary considerably with magnetic local time, radial distance and latitude. Furthermore the interaction of the waves with the particles is usually nonlinear. These factors present a major challenge to test and verify the theories. Here we discuss the role of several types of waves, including whistler mode chorus, plasmaspheric hiss, magnetosonic and electromagnetic ion cyclotron waves, in relation to radiation belt and ring current dynamics. We present simulations of the radiation belts using the BAS radiation belt model which includes the effects of chorus, hiss and EMIC waves along with radial diffusion. We show that chorus waves are required to form the peaks in the electron phase space density during storms, and that this occurs inside geostationary orbit. We compare simulations against observations in medium Earth orbit and the new results from Van Allen probes mission that shows conclusive evidence for a local electron acceleration process near L=4.5. We show the relative importance of plasmaspheric hiss and chorus and the location of the plasmapause for radiation belt dynamics near L=4.5 and demonstrate the losses due to EMIC waves that should occur at high energies. Finally we show how improving our basic physical understanding through missions such as Van Allen probes go to improve space weather forecasting in projects such as SPACECAST and have a direct benefit to society.

Global electric field determination in the Earth's outer magnetosphere using energetic charged particles

NASA Technical Reports Server (NTRS)

Eastman, Timothy E.; Sheldon, R.; Hamilton, D.

1995-01-01

Although many properties of the Earth's magnetosphere have been measured and quantified in the past 30 years since it was discovered, one fundamental measurement (for zeroth order MHD equilibrium) has been made infrequently and with poor spatial coverage - the global electric field. This oversight is due in part to the neglect of theorists. However, there is renewed interest in the convection electric field because it is now realized to be central to many magnetospheric processes, including the global MHD equilibrium, reconnection rates, Region 2 Birkeland currents, magnetosphere ionosphere coupling, ring current and radiation belt transport, substorm injections, and several acceleration mechanisms. Unfortunately the standard experimental methods have not been able to synthesize a global field (excepting the pioneering work of McIlwain's geostationary models) and we are left with an overly simplistic theoretical field, the Volland-Stern electric field model. Single point measurements of the plasmapause were used to infer the appropriate amplitudes of this model, parameterized by K(sub p). Although this result was never intended to be the definitive electric field model, it has gone nearly unchanged for 20 years. The analysis of current data sets requires a great deal more accuracy than can be provided by the Volland-Stern model. The variability of electric field shielding has not been properly addressed although effects of penetrating magnetospheric electric fields has been seen in mid-and low-latitude ionospheric data sets. The growing interest in substorm dynamics also requires a much better assessment of the electric fields responsible for particle injections. Thus we proposed and developed algorithms for extracting electric fields from particle data taken in the Earth's magnetosphere. As a test of the effectiveness of these new techniques, we analyzed data taken by the AMPTE/CCE spacecraft in equatorial orbit from 1984 to 1989.

Review of GEM Radiation Belt Dropout and Buildup Challenges

NASA Astrophysics Data System (ADS)

Tu, Weichao; Li, Wen; Morley, Steve; Albert, Jay

2017-04-01

In Summer 2015 the US NSF GEM (Geospace Environment Modeling) focus group named "Quantitative Assessment of Radiation Belt Modeling" started the "RB dropout" and "RB buildup" challenges, focused on quantitative modeling of the radiation belt buildups and dropouts. This is a community effort which includes selecting challenge events, gathering model inputs that are required to model the radiation belt dynamics during these events (e.g., various magnetospheric waves, plasmapause and density models, electron phase space density data), simulating the challenge events using different types of radiation belt models, and validating the model results by comparison to in situ observations of radiation belt electrons (from Van Allen Probes, THEMIS, GOES, LANL/GEO, etc). The goal is to quantitatively assess the relative importance of various acceleration, transport, and loss processes in the observed radiation belt dropouts and buildups. Since 2015, the community has selected four "challenge" events under four different categories: "storm-time enhancements", "non-storm enhancements", "storm-time dropouts", and "non-storm dropouts". Model inputs and data for each selected event have been coordinated and shared within the community to establish a common basis for simulations and testing. Modelers within and outside US with different types of radiation belt models (diffusion-type, diffusion-convection-type, test particle codes, etc.) have participated in our challenge and shared their simulation results and comparison with spacecraft measurements. Significant progress has been made in quantitative modeling of the radiation belt buildups and dropouts as well as accessing the modeling with new measures of model performance. In this presentation, I will review the activities from our "RB dropout" and "RB buildup" challenges and the progresses achieved in understanding radiation belt physics and improving model validation and verification.

Data Prospecting with CORPRAL: Pre-attentive Vision Model at Work

NASA Astrophysics Data System (ADS)

Galkin, I. A.; Reinisch, B. W.; Khmyrov, G. M.; Kozlov, A. V.; Grinstein, J.; Fung, S. F.

2005-12-01

The Cognitive Online Rpi Plasmagram Rating Algorithm (CORPRAL) is the automated data prospecting tool developed to find interesting examples of signal propagation in the 1.2 million plasmagram image archive from the Radio Plasma Imager (RPI) onboard the IMAGE spacecraft. The RPI instrument is a spaceborne radar whose transmitted radio waves may reflect from important magnetospheric structures, such as the plasmapause and the magnetopause, and return to the spacecraft location to be detected. The CORPRAL prospector draws attention of the human analysts to the RPI plasmagrams that contain traces of remote reflections (~18% of all images), thus helping to relieve the search efforts in the otherwise overwhelming RPI data repository. To find the echo traces in plasmagrams, CORPRAL employs a pre-attentive vision model that replicates human ability to identify important objects in the field of view without willful concentration of attention. The importance of such objects is determined by their `saliency', the ability to stand out against the background. The saliency evaluation is done subconsciously, without a priori concepts of the object shape. The RPI imagery dataset providesd an excellent testbed for studies of the model performance on low saliency objects immersed in irregular background noise. The paper discusses results of statistical evaluation of the CORPRAL performance on a collection of ~25,000 plasmagram images interpreted manually. Overall accuracy of plasmagram interpretation varies depending on the applied measuring program but remains in the mid-90% range. As the prevalence of plasmagrams that contain traces goes below 10%, we do observe lower positive predicted values (PPV) of the CORPRAL analysis (~50%), indicating that automatically selected plasmagrams are interesting only with 50% chance. We will discuss future development efforts and provide examples and scenarios where RPI data prospecting is instrumental in knowledge discovery.

Statistical analysis of plasmaspheric magnetosonic mode waves from Van Allen Probes observations

NASA Astrophysics Data System (ADS)

Nomura, K.; Miyoshi, Y.; Keika, K.; Shoji, M.; Kurita, S.; Kitamura, N.; Machida, S.; Santolik, O.; Kletzing, C.; Boardsen, S. A.

2015-12-01

Magnetosonic waves (MSWs) are electromagnetic emissions whose properites can be described by the cold plasma extraordinary mode, which are typically generated at frequencies (f) between the proton cyclotron frequency (fcp) and the lower hybrid resonant frequency. It has been suggested that MSWs can contribute to the acceleration of relativistic electrons in the radiation belts. In this study, we investigate the Poynting vector of plasmaspheric MSWs using the spectral matrix data from the EMFISIS instrument onboard the Van Allen Probes spacecraft. We derived the polarization and planarity from the spectrum matrix using the SVD method (Santolik et al., 2003) and also estimated the Poynting vector. The planarity is used as a proxy to distinguish presence of a single wave vector from mixture of waves propagating in different directions. The Poynting vector of MSWs with high planarity shows that the MSWs are observed to propagate radially as well as longitudinally. The occurrence probability of the propagation directions depends on the geomagnetic activities. During the geomagnetically quiet periods　(Kp < 3), the percentage of inward, outward, and longitudinal propagations of MSWs at 60 Hz are 22%, 36% and 42% respectively. On the other hand, during the geomagnetically active periods (Kp > 5), the percentages are 53%, 21%, and 26%, respectively. The result indicates that the MSWs tend to propagate inward during the geomagnetically active periods. Since the fundamental frequency of the ion Bernstein mode would be local cyclotron frequency, we also investigate the source of MSWs from the minimum frequency of MSWs. It is found that a large number of MSWs tend to be generated at L=3.0-3.5 inside the plasmapause. We will also discuss the validity of the Poynting flux computation as a function of f/fcp.

Unusual whistler with very large dispersion near the magnetopause: Geotail observation and ray-tracing modeling

NASA Astrophysics Data System (ADS)

Nagano, I.; Wu, X.-Y.; Yagitani, S.; Miyamura, K.; Matsumoto, H.

1998-06-01

A case of highly dispersed (~860 s1/2) whistler-like ELF (700-960 Hz) wave was detected with the waveform capture (WFC) receiver aboard the Geotail satellite during a dayside magnetopause skimming. Features of the single event distinguish it from the usual falling tone discrete emissions. By ray-tracing and full-wave calculation, the accessibility of the waves from a ground source of a distorted model magnetosphere were investigated. We propose that a lightning discharge at high latitudes is the most plausible source of the event via a special propagation effect revealed by the ray tracing. We demonstrate that the observed large wavenormal angle with respect to the geomagnetic field, the unusually large level of dispersion, and the lack of the expected nose frequency might be attributable to the frequency-dependent nonducted paths to the satellite. The rare occurrence may partly be caused by the Landau damping by the convecting suprathermal electron beams of several hundred eV. It is also shown that the multiple-hop magnetospherically reflected (MR) whistlers from middle latitudes, though being refracted to higher L shells by the plasmapause, are unable to reach the outer magnetosphere. Interhemisphere ducted propagation is possible for ELF waves along a narrow, modestly (15% or more) enhanced flux tube and shows an upper cutoff frequency governed by the high-latitude minimum-magnetic field ``horns'' regions and the duct enhancement and diameter. A full-wave calculation also implies no lower-frequency cutoff in the upward ionospheric transmission of lightning radiation down to 200 Hz. Because of the complexity of the various effects that influence the propagation from a ground source and the very low occurrence, effective whistler mode waves diagnostics of the highly variable outer magnetosphere are at present beyond our reach.

Cross-scale observations of the 2015 St. Patrick's day storm: THEMIS, Van Allen Probes, and TWINS

DOE PAGES

Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; ...

2016-12-10

In this paper, we present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick's Day) storm, by Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes (Radiation Belt Storm Probes), and Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), plus upstream ACE/Wind solar wind data. THEMIS crossed the bow shock or magnetopause 22 times and observed the magnetospheric compression that initiated the storm. Empirical models reproduce these boundary locations within 0.7 R E. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 R E. Before the storm, Van Allen Probesmore » measured quiet double-nose proton spectra in the region of corotating cold plasma. About 15 min after a 0605 UT dayside southward turning, Van Allen Probes captured the onset of inner magnetospheric convection, as a density decrease at the moving corotation-convection boundary (CCB) and a steep increase in ring current (RC) proton flux. During the first several hours of the storm, Van Allen Probes measured highly dynamic ion signatures (numerous injections and multiple spectral peaks). Sustained convection after ~1200 UT initiated a major buildup of the midnight-sector ring current (measured by RBSP A), with much weaker duskside fluxes (measured by RBSP B, THEMIS a and THEMIS d). A close conjunction of THEMIS d, RBSP A, and TWINS 1 at 1631 UT shows good three-way agreement in the shapes of two-peak spectra from the center of the partial RC. A midstorm injection, observed by Van Allen Probes and TWINS at 1740 UT, brought in fresh ions with lower average energies (leading to globally less energetic spectra in precipitating ions) but increased the total pressure. Finally, the cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure.« less

Plasma observations at the Earth's magnetic equator

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

Olsen, R.C.; Shawhan, S.D.; Gallagher, D.L.

1987-03-01

The magnetic equator provides a unique location for thermal plasma and plasma wave measurements. Plasma populations are found to be confined within a few degrees latitude of the equator, particularly the ions. The equatorially trapped ion population is found to be primarily hydrogen, and the authors find little evidence for preferential heating of heavier ions. Helium is occasionally found to be heated along with the protons, and forms about 10% of the equatorially trapped populations at such times, similar to the percentage of He{sup +} in the cold, core plasma of the plasmasphere. One case of a heated O{sup +}more » component was found; at the 0.1% level it generally comprises in the outer plasmasphere core plasma. The heated H{sup +} ions can be characterized by a bi-Maxwellian with kT{sub {parallel}} = 0.5-1.0 eV, and kT = 5-50 eV, with a density of 10-100 cm{sup {minus}3}. The total plasma density, as inferred from the plasma wave instrument measurements of the upper hybrid measurements of the upper hybrid resonance (UHR), is relatively constant with latitude, occasionally showing a local minimum at the magnetic equator, even though the ion flux has increased substantially. The first measurements of the equatorially trapped plasma and coincident UHR measurements show that the trapped plasma is a feature of the plasmapause region, found at total plasma densities of 20-200 cm{sup {minus}3}. The warm, trapped plasma is found in conjunction with equatorial noise, a plasma wave feature found at frequencies near 100 Hz, with a broad spectrum generally found between the proton gyrofrequency at the low frequency edge and the geometric mean gyrofrequency at the high frequency edge. This latter frequency is generally the lower hybrid resonance (LHR) for a proton-electron plasma. Sharp spatial boundaries are occasionally found with latitude, delimiting the equatorially trapped plasma.« less

EMIC waves covering wide L shells: MMS and Van Allen Probes observations

NASA Astrophysics Data System (ADS)

Yu, Xiongdong; Yuan, Zhigang; Huang, Shiyong; Wang, Dedong; Li, Haimeng; Qiao, Zheng; Yao, Fei

2017-07-01

During 04:45:00-08:15:00 UT on 13 September in 2015, a case of Electromagnetic ion cyclotron (EMIC) waves covering wide L shells (L = 3.6-9.4), observed by the Magnotospheric Multiscale 1 (MMS1) are reported. During the same time interval, EMIC waves observed by Van Allen Probes A (VAP-A) only occurred just outside the plasmapause. As the Van Allen Probes moved outside into a more tenuous plasma region, no intense waves were observed. Combined observations of MMS1 and VAP-A suggest that in the terrestrial magnetosphere, an appropriately dense background plasma would make contributions to the growth of EMIC waves in lower L shells, while the ion anisotropy, driven by magnetospheric compression, might play an important role in the excitation of EMIC waves in higher L shells. These EMIC waves are observed over wide L shells after three continuous magnetic storms, which suggests that these waves might obtain their free energy from those energetic ions injected during storm times. These EMIC waves should be included in radiation belt modeling, especially during continuous magnetic storms. Moreover, two-band structures separated in frequencies by local He2+ gyrofrequencies were observed in large L shells (L > 6), implying sufficiently rich solar wind origin He2+ likely in the outer ring current. It is suggested that multiband-structured EMIC waves can be used to trace the coupling between solar wind and the magnetosphere.tract type="synopsis">le type="main">Plain Language SummaryThe spatial distribution of EMIC waves is an opening question. With combined observations of MMS and Van Allen Probes, this paper has reported EMIC waves covering wide L shells. Moreover, two-band structures separated in frequencies by local He2+ gyrofrequencies were observed in large L shells (L > 6), implying sufficiently rich solar wind origin He2+ likely in the outer ring current. The result is helpful to revealing the spatial distribution and role of He2+ in excitation of EMIC waves.

Cross-scale observations of the 2015 St. Patrick's day storm: THEMIS, Van Allen Probes, and TWINS

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

Goldstein, J.; Angelopoulos, V.; De Pascuale, S.

In this paper, we present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick's Day) storm, by Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes (Radiation Belt Storm Probes), and Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), plus upstream ACE/Wind solar wind data. THEMIS crossed the bow shock or magnetopause 22 times and observed the magnetospheric compression that initiated the storm. Empirical models reproduce these boundary locations within 0.7 R E. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 R E. Before the storm, Van Allen Probesmore » measured quiet double-nose proton spectra in the region of corotating cold plasma. About 15 min after a 0605 UT dayside southward turning, Van Allen Probes captured the onset of inner magnetospheric convection, as a density decrease at the moving corotation-convection boundary (CCB) and a steep increase in ring current (RC) proton flux. During the first several hours of the storm, Van Allen Probes measured highly dynamic ion signatures (numerous injections and multiple spectral peaks). Sustained convection after ~1200 UT initiated a major buildup of the midnight-sector ring current (measured by RBSP A), with much weaker duskside fluxes (measured by RBSP B, THEMIS a and THEMIS d). A close conjunction of THEMIS d, RBSP A, and TWINS 1 at 1631 UT shows good three-way agreement in the shapes of two-peak spectra from the center of the partial RC. A midstorm injection, observed by Van Allen Probes and TWINS at 1740 UT, brought in fresh ions with lower average energies (leading to globally less energetic spectra in precipitating ions) but increased the total pressure. Finally, the cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure.« less

The Dst Recovery Near Substorm Onset Due to the Transformation of the Blocked Cross-Tail Current into the Substorm Current Wedge

NASA Astrophysics Data System (ADS)

McWilliams, K. A.; Sofko, G. J.; Hussey, G. C.; Reimer, A. S.

2016-12-01

During the growth phase the convex curvature of the lobe field lines permits eastward curvature current to dominate on those lobe lines, which blocks the westward cross-tail current (XTJ). The blocked XTJ (BXTJ) is diverted earthward through the tailward portion of the transition plasmasheet (TPS) region of predominantly dipole lines tailward of the plasmapause. The flow shear of the BXTJ in the TPS produces a downward meridional FAC that results in the pre-onset proton arc in the subauroral region. This ionospheric signature of the growth phase lasts for about an hour, ending about 15 minutes before onset, when the pre-onset electron arc appears. Ions in the outer radiation belt precipitate equatorward of the meridional FAC system, because they are on stretched field lines tailward of the ion trapping boundary. The ion precipitation causes the ionospheric conductivity to increases substantially, providing a new high-conductivity route in the ionosphere for the BXTJ. This diversion of the BXTJ forms the Substorm Current Wedge. During the pre-onset proton arc interval, the intensification of the ring current and the flow of the BXTJ cause the Dst index to fall. When the BXTJ is diverted into the ionosphere and forms the substorm current wedge, it produces a northward magnetic field that causes Dst to have a brief positive deflection of 15-20 nT, despite all indications that the ring current continues to grow. The positive Dst deflection is the result both of the loss of the BXTJ from the tailward portion of the TPS and of its new northward field generated by its new route along the SCW. Note that there are two disruptions of the XTJ, first the early growth phase lobe line blocking that diverts the BXTJ earthward into the TPS region, and second (over an hour later, near onset) by the transformation of the BXTJ into the SCW.

New Results About the Earth’s Van Allen Radiation Belts

NASA Astrophysics Data System (ADS)

Baker, Daniel

2015-01-01

The first great scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or 'belts', of very high-energy magnetically trapped charged particles. Early observations of the radiation environment clearly indicated that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies showed that electrons in the energy range 100 keV < E< 1 MeV often populated both the inner and outer zones with a pronounced 'slot' region relatively devoid of energetic electrons existing between them. This two-belt structure for the Van Allen moderate-energy electron component was explained as being due to strong interactions of electrons with electromagnetic waves just inside the cold plasma (plasmapause) boundary. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. However, recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed wholly unexpected properties of the radiation belts, especially at highly relativistic (E > 2 MeV) and ultra-relativistic (E > 5 MeV) kinetic energies. In this presentation we show using high spatial and temporal resolution data from the Relativistic Electron-Proton Telescope (REPT) experiment on board the Van Allen Probes that multiple belts can exist concurrently and that an exceedingly sharp inner boundary exists for ultra-relativistic electrons. Using additionally available Van Allen Probes data, we demonstrate that these remarkable features of energetic electrons are not due to a physical boundary within Earth's intrinsic magnetic field. Neither is it likely that human-generated electromagnetic transmitter wave fields might produce such effects. Rather, we conclude from these unique measurements that slow natural inward radial diffusion combined with weak, but persistent, wave-particle pitch angle scattering deep inside the Earth's magnetosphere can conspire to create an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate.

A Parametric Study of the Cold Plasma Refilling Rate on the Plasmasphere and Inner Magnetosphere Dynamics during the 17-March-2013 and 28-June-2013 Magnetic Storms

NASA Astrophysics Data System (ADS)

Lemon, C.; Bishop, R. L.; Coster, A. J.; Nikoukar, R.; Chen, M.; Turner, D. L.; Roeder, J. L.; Shumko, M.; Payne, C.; Bhatt, R.

2017-12-01

Magnetosphere-ionosphere coupling is a complex process, and researchers must consider a number of factors: particle transport in the electric and magnetic fields drives plasma from the high latitude tail to the mid-latitude inner magnetosphere; particle precipitation into the ionosphere, which is frequently driven by wave-particle interactions, enhances the ionospheric conductivities; feedback of the ionospheric conductivities on the electric fields determines how well the convection electric field penetrates to the mid-latitude ionosphere; and the erosion and refilling of cold plasma in the plasmasphere substantially determines the mass of plasma on magnetospheric field lines and the subsequent wave environment that drives particle precipitation. While we model all of these processes, in this presentation we focus on the role of the plasmasphere and its role in M-I coupling. We present RCM-E simulations in which particle transport through self-consistent fields controls the drainage of the plasmasphere, an outflow model determines the plasmasphere refilling rate, and electron and ion precipitation influences the electric field by enhancing the ionospheric conductivity. The plasmasphere significantly affects the spatial structure of the wave environment and electron precipitation rates. This impacts the dynamics of the sub-auroral polarization stream (SAPS) in the pre-midnight region equatorward of the auroral boundary, which itself drives erosion of the plasmasphere through strong westward electric fields near the plasmapause. We present comparisons with Van Allen Probes, THEMIS, the Plasmasphere Data Assimilation (PDA) model, and line-of-sight observations from Millstone Hill ISR and space-based GPS receivers, showing how our modeled plasmasphere compares with observational data during the 17-March-2013 and 28-June-2013 magnetic storms. To better understand refilling, we focus particular attention on densities in the recently-depleted flux tubes in the plasmasphere trough. We compare several empirical models of the plasmasphere refilling rate to see which ones give the best agreement, and through parametric simulations we systematically investigate the effect of varying the local time and L dependence of the refilling rate.

Nonlinear VLF Wave Physics in the Radiation Belts

NASA Astrophysics Data System (ADS)

Crabtree, C. E.; Tejero, E. M.; Ganguli, G.; Mithaiwala, M.; Rudakov, L.; Hospodarsky, G. B.; Kletzing, C.

2014-12-01

Electromagnetic VLF waves, such as whistler mode waves, both control the lifetime of trapped electrons in the radiation belts by pitch-angle scattering and are responsible for the energization of electrons during storms. Traditional approaches to understanding the influence of waves on trapped electrons have assumed that the wave characteristics (frequency spectrum, wave-normal angle distribution, etc.) were both stationary in time and amplitude independent from event to event. In situ data from modern satellite missions, such as the Van Allen probes, are showing that this assumption may not be justified. In addition, recent theoretical results [Crabtree et al. 2012] show that the threshold for nonlinear wave scattering can often be met by naturally occurring VLF waves in the magnetosphere, with wave magnetic fields of the order of 50-100 pT inside the plasmapause. Nonlinear wave scattering (Nonlinear Landau Damping) is an amplitude dependent mechanism that can strongly alter VLF wave propagation [Ganguli et al. 2010], primarily by altering the direction of propagation. Laboratory results have confirmed the dramatic change in propagation direction when the pump wave has sufficient amplitude to exceed the nonlinear threshold [Tejero et al. 2014]. Nonlinear scattering can alter the macroscopic dynamics of waves in the radiation belts leading to the formation of a long-lasting wave-cavity [Crabtree et al. 2012] and, when amplification is present, a multi-pass amplifier [Ganguli et al., 2012]. Such nonlinear wave effects can dramatically reduce electron lifetimes. Nonlinear wave dynamics such as these occur when there are more than one wave present, such a condition necessarily violates the assumption of traditional wave-normal analysis [Santolik et al., 2003] which rely on the plane wave assumption. To investigate nonlinear wave dynamics using modern in situ data we apply the maximum entropy method [Skilling and Bryan, 1984] to solve for the wave distribution function [Storey and Lefeuvre, 1979] to yield the power distribution as a function of wave-normal angle and local azimuthal angle. We have validated this technique in the NRL space chamber and applied this methodology to Van Allen probe data to demonstrate that traditional wave-normal analaysis can give misleading results when multiple waves are present.

Analyzing Electric Field Morphology Through Data-Model Comparisons of the GEM IM/S Assessment Challenge Events

NASA Technical Reports Server (NTRS)

Liemohn, Michael W.; Ridley, Aaron J.; Kozyra, Janet U.; Gallagher, Dennis L.; Thomsen, Michelle F.; Henderson, Michael G.; Denton, Michael H.; Brandt, Pontus C.; Goldstein, Jerry

2006-01-01

The storm-time inner magnetospheric electric field morphology and dynamics are assessed by comparing numerical modeling results of the plasmasphere and ring current with many in situ and remote sensing data sets. Two magnetic storms are analyzed, April 22,2001 and October 21-23,2001, which are the events selected for the Geospace Environment Modeling (GEM) Inner Magnetosphere/Storms (IM/S) Assessment Challenge (IMSAC). The IMSAC seeks to quantify the accuracy of inner magnetospheric models as well as synthesize our understanding of this region. For each storm, the ring current-atmosphere interaction model (RAM) and the dynamic global core plasma model (DGCPM) were run together with various settings for the large-scale convection electric field and the nightside ionospheric conductance. DGCPM plasmaspheric parameters were compared with IMAGE-EUV plasmapause extractions and LANL-MPA plume locations and velocities. RAM parameters were compared with Dst*, LANL-MPA fluxes and moments, IMAGE-MENA images, and IMAGE-HENA images. Both qualitative and quantitative comparisons were made to determine the electric field morphology that allows the model results to best fit the plasma data at various times during these events. The simulations with self-consistent electric fields were, in general, better than those with prescribed field choices. This indicates that the time-dependent modulation of the inner magnetospheric electric fields by the nightside ionosphere is quite significant for accurate determination of these fields (and their effects). It was determined that a shielded Volland-Stern field description driven by the 3-hour Kp index yields accurate results much of the time, but can be quite inconsistent. The modified Mcllwain field description clearly lagged in overall accuracy compared to the other fields, but matched some data sets (like Dst*) quite well. The rankings between the simulations varied depending on the storm and the individual data sets, indicating that each field description did well for some place, time, and energy range during the events, as well as doing less well in other places, times, and energies. Several unresolved issues regarding the storm-time inner magnetospheric electric field are discussed.

New Generation of ELF/VLF Wave Injection Experiments for HAARP

NASA Astrophysics Data System (ADS)

Sonwalkar, V. S.; Reddy, A.; Watkins, B. J.

2016-12-01

We present a ray tracing study to investigate the feasibility of a new generation of wave injection experiments from HAARP transmitter (L 4.9). Highly successful whistler mode wave injection experiments from SIPLE station, Antarctica, have established the importance of such experiments to study magnetospheric wave-particle interactions, and for cold and hot plasma diagnostics [Helliwell and Katsufrakis, 1974; Carpenter and Miller, 1976; Sonwalkar et al., 1997]. Modulated heating experiments from HAARP have shown that it is possible to launch ELF/VLF waves into the magnetosphere that can be observed on the ground after one-, two-, and multi-hop ducted propagation [Inan et al., 2004]. Recent research has also shown that ionospheric heating experiments using HAARP can lead to the formation of magnetospheric ducts [e.g. Milikh et al., 2010; Fallen et al., 2011]. Collectively, these results indicate that the HAARP (or similar) transmitter can be used first to form ducts on nearby L shells, and then to inject and trap transmitter generated ELF/VLF waves in those ducts. Ray tracing studies using a model magnetosphere shows that ELF/VLF waves in a few kilohertz range can be trapped in ducts with L shells near the HAARP transmitter. For example, 1.5 kHz waves injected from L shell = 4.9 and altitude = 200 km can be trapped in ducts located within 0.3 L of the transmitter L-shell. The duct parameters needed for ray-trapping are typically duct width dL 0.1-0.3 and duct enhancement factor dNe/Ne 10-20% or more. The location of plasmapause with respect to transmitter plays a role in the nature of trapping. The duct locations and parameters required for trapping ELF/VLF waves inside the ducts are consistent with past observations of ducts generated by the HAARP transmitter. Ray tracing calculations provide trapped wave normal angles, time delays, resonant energetic electron energy, estimates of wave intensity inside the duct, on the ground, and on satellites such DEMETER, Van Allen probe, and planned DSX. We discuss the potential of a new generation of wave injection experiments from HAARP transmitter to investigate: duct and ELF/VLF generation by high power HF transmitters, whistler mode wave propagation and wave particle interactions, and cold and hot plasma diagnostics.

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.

Initial report of the High Frequency Analyzer (HFA) onboard the ARASE (ERG) Satellite: Observations of the plasmasphere evolution and auroral kilometric radiation from the both hemisphere

NASA Astrophysics Data System (ADS)

Kumamoto, A.; Tsuchiya, F.; Kasahara, Y.; Kasaba, Y.; Kojima, H.; Yagitani, S.; Ishisaka, K.; Imachi, T.; Ozaki, M.; Matsuda, S.; Shoji, M.; Matsuoka, A.; Katoh, Y.; Miyoshi, Y.; Shinohara, I.; Obara, T.

2017-12-01

High Frequency Analyzer (HFA) is a subsystem of the Plasma Wave Experiment (PWE) onboard the ARASE (ERG, Exploration of energization and Radiation in Geospace) spacecraft for observation of radio and plasma waves in a frequency range from 0.01 to 10 MHz. In ARASE mission, HFA is expected to perform the following observations: (1) Upper hybrid resonance (UHR) waves in order to determine the electron number density around the spacecraft. (2) Magnetic field component of the chorus waves in a frequency range from 20 kHz to 100 kHz. (3) Radio and plasma waves excited via wave particle interactions and mode conversion processes in storm-time magnetosphere.HFA is operated in the following three observation modes: EE-mode, EB-mode, and PP-mode. In far-Earth region, HFA is operated in EE-mode. Spectrogram of two orthogonal or right and left-handed components of electric field in perpendicular directions to the spin axis of the spacecraft are obtained. In the near-Earth region, HFA is operated in EB-mode. Spectrogram of one components of electric field in perpendicular direction to the spin plane, and one component of the magnetic field in parallel direction to the spin axis are obtained. In EE and EB-modes, the frequency range from 0.01 to 10 MHz are covered with 480 frequency steps. The time resolution is 8 sec. We also prepared PP mode to measure the locations and structures of the plasmapause at higher resolution. In PP-mode, spectrogram of one electric field component in a frequency range from 0.01-0.4 MHz (PP1) or 0.1-1 MHz (PP2) can be obtained at time resolution of 1 sec.After the successful deployment of the wire antenna and search coils mast and initial checks, we could start routine observations and detect various radio and plasma wave phenomena such as upper hybrid resonance (UHR) waves, electrostatic electron cyclotron harmonic (ESCH) waves, auroral kilometric radiation (AKR), kilometric continuum (KC) and Type-III solar radio bursts. In the presentation, we will report the initial results based on the datasets obtained since January 2017 focusing on the analyses of plasmasphere evolution by semi-automatic identification of UHR frequency, and AKR from the both hemisphere based on polarization measurement.

Global Dayside Ionospheric Uplift and Enhancement Associated with Interplanetary Electric Fields

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce; Mannucci, Anthony; Iijima, Byron; Abdu, Mangalathayil Ali; Sobral, Jose Humberto A.; Gonzalez, Walter; Guarnieri, Fernando; Tsuda, Toshitaka; Saito, Akinori; Yumoto, Kiyohumi;

Observational evidence of competing source, loss, and transport processes for relativistic electrons in Earth's outer radiation belt

NASA Astrophysics Data System (ADS)

Turner, Drew; Mann, Ian; Usanova, Maria; Rodriguez, Juan; Henderson, Mike; Angelopoulos, Vassilis; Morley, Steven; Claudepierre, Seth; Li, Wen; Kellerman, Adam; Boyd, Alexander; Kim, Kyung-Chan

Earth’s outer electron radiation belt is a region of extreme variability, with relativistic electron intensities changing by orders of magnitude over time scales ranging from minutes to years. Extreme variations of outer belt electrons ultimately result from the relative impacts of various competing source (and acceleration), loss, and transport processes. Most of these processes involve wave-particle interactions between outer belt electrons and different types of plasma waves in the inner magnetosphere, and in turn, the activity of these waves depends on different solar wind and magnetospheric driving conditions and thus can vary drastically from event to event. Using multipoint analysis with data from NASA’s Van Allen Probes, THEMIS, and SAMPEX missions, NOAA’s GOES and POES constellations, and ground-based observatories, we present results from case studies revealing how different source/acceleration and loss mechanisms compete during active periods to result in drastically different distributions of outer belt electrons. By using a combination of low-Earth orbiting and high-altitude-equatorial orbiting satellites, we briefly review how it is possible to get a much more complete picture of certain wave activity and electron losses over the full range of MLTs and L-shells throughout the radiation belt. We then show example cases highlighting the importance of particular mechanisms, including: substorm injections and whistler-mode chorus waves for the source and acceleration of relativistic electrons; magnetopause shadowing and wave-particle interactions with EMIC waves for sudden losses; and ULF wave activity for driving radial transport, a process which is important for redistributing relativistic electrons, contributing both to acceleration and loss processes. We show how relativistic electron enhancement events involve local acceleration that is consistent with wave-particle interactions between a seed population of 10s to 100s of keV electrons, with a source in the plasma sheet, and chorus waves. We show how sudden losses during outer belt dropout events are dominated at higher L-shells (L>~4) by magnetopause shadowing and outward radial transport, which is effective over the full ranges of energy and equatorial pitch angle of outer belt electrons, but at lower L-shells near the plasmapause, energy and pitch angle dependent losses can also occur and are consistent with rapid scattering by interactions between relativistic electrons and EMIC waves. We show cases demonstrating how these different processes occur simultaneously during active periods, with relative effects that vary as a function of L-shell and electron energy and pitch angle. Ultimately, our results highlight the complexity of competing source/acceleration, loss, and transport processes in Earth’s outer radiation belt and the necessity of using multipoint observations to disambiguate between them for future studies.

The Plasmasphere as "Seen" by the IMAGE Mission

NASA Technical Reports Server (NTRS)

Gallagher, D. L.; Green, J. L.; Fung, S. F.; Benson, R. F.; Sandel, B. R.; Carpenter, D. L.

1999-01-01

The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) is the first mission designed exclusively to remotely measure the magnetosphere. As such, it will reveal the ring current, plasmasphere, polar cusp, and magnetopause as whole extended, interacting systems. For the first time, our impressions of the global magnetosphere, synthesized through many years of whistler and in situ measurement, will be replaced by images. The overall morphology of each system of plasma and the correspondence of changes between them in response to the sun and solar wind will become available. The Extreme Ultraviolet Imager (EUV) and the Radio Plasma Imager (RPI) are the two IMAGE instruments which will remotely measure and image the plasmasphere. What we expect to "see" from these instruments and how it may be interpreted is the subject of this presentation. The EUV instrument includes three optical cameras, with an almost 90 degree field of view, transverse to the spin axis. EUV is designed to see He+ ions in resonantly scatter solar light at 30.4rim. The IMAGE spacecraft will spin with a period of about 2 minutes, with its spin axis parallel to the orbit normal. The IMAGE orbit will be highly inclined, with a high latitude apogee at a geocentric distance of 8RE and perigee of about 1.2RE. The normal observing integration time of 10 minutes will easily see to the outer edge of the plasmasphere. The RPI instrument makes use of three orthoganal dipole antennas: two in the spin plane with a tip-to-tip length of 500m and one along the spin axis with a length of 20 meters. Using coded pulse transmissions, the RPI instrument will broadcast from 3kHz to 3MHz. With one minute resolution, plasma densities from about 0.1 cm(exp -3) to 100,000 cm(exp -3), along with line-of-sight bulk velocities and locations, will be obtained from all returned radio wave signals. When transmitting from the high latitude magnetospheric cavity, RPI will measure density profiles for the major plasma structures in the magnetosphere, including the magnetopause, polar cusp, and plasmasphere. RPI should also see isolated density irregularities and possibly the plasma sheet. Observations The EUV instrument will return line-of-sight integrated images through the optically thin helium medium of the plasmasphere and magnetosphere. A variety of techniques have been suggested for the translation of the images into physically useful data, such as plasmapause location and three dimensional density distribution. The RPI instrument will return quantitative density values and line-of-sight velocity as a function of position along reflecting wave propagation paths. How they may be used individually and together to study plasmaspheric dynamics and global structure will be discussed. Attention will also be given to the data products and how access to IMAGE data will be provided by the IMAGE team and the NSSDC.

Radial diffusion with outer boundary determined by geosynchronous measurements: Storm and post-storm intervals

NASA Astrophysics Data System (ADS)

Chu, F.; Haines, P.; Hudson, M.; Kress, B.; Freidel, R.; Kanekal, S.

2007-12-01

Work is underway by several groups to quantify diffusive radial transport of radiation belt electrons, including a model for pitch angle scattering losses to the atmosphere. The radial diffusion model conserves the first and second adiabatic invariants and breaks the third invariant. We have developed a radial diffusion code which uses the Crank Nicholson method with a variable outer boundary condition. For the radial diffusion coefficient, DLL, we have several choices, including the Brautigam and Albert (JGR, 2000) diffusion coefficient parameterized by Kp, which provides an ad hoc measure of the power level at ULF wave frequencies in the range of electron drift (mHz), breaking the third invariant. Other diffusion coefficient models are Kp-independent, fixed in time but explicitly dependent on the first invariant, or energy at a fixed L, such as calculated by Elkington et al. (JGR, 2003) and Perry et al. (JGR, 2006) based on ULF wave model fields. We analyzed three periods of electron flux and phase space density (PSD) enhancements inside of geosynchronous orbit: March 31 - May 31, 1991, and July 2004 and Nov 2004 storm intervals. The radial diffusion calculation is initialized with a computed phase space density profile for the 1991 interval using differential flux values from the CRRES High Energy Electron Fluxmeter instrument, covering 0.65 - 7.5 MeV. To calculate the initial phase space density, we convert Roederer L* to McIlwain's L- parameter using the ONERA-DESP program. A time averaged model developed by Vampola1 from the entire 14 month CRRES data set is applied to the July 2004 and Nov 2004 storms. The online CRESS data for specific orbits and the Vampola-model flux are both expressed in McIlwain L-shell, while conversion to L* conserves phase space density in a distorted non-dipolar magnetic field model. A Tsyganenko (T04) magnetic field model is used for conversion between L* and L. The outer boundary PSD is updated using LANL GEO satellite fluxes. After calculating the phase space density time evolution for the two storms and post-injection interval (March 31 - May 31, 1991), we compare results with SAMPEX measurements. A better match with SAMPEX measurements is obtained with a variable outer boundary, also with a Kp-dependent diffusion coefficient, and finally with an energy and L-dependent loss term (Summers et al., JGR, 2004), than with a time-independent diffusion coefficient and a simple Kp-parametrized loss rate and location of the plasmapause. Addition of a varying outer boundary which incorporates measured fluxes at geosynchronous orbit using L* has the biggest effect of the three parametrized variations studied. 1Vampola, A.L., 1996, The ESA Outer Zone Electron Model Update, Environment Modelling for Spaced-based Applications, ESA SP-392, ESTEC, Nordwijk, NL, pp. 151-158, W. Burke and T.-D. Guyenne, eds.

Self-consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 2. Wave Induced Ring Current Precipitation and Thermal Electron Heating

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.; Liemohn, M. W.

2007-01-01

This paper continues presentation and discussion of the results from our new global self-consistent theoretical model of interacting ring current ions and propagating electromagnetic ion cyclotron waves [Khazanov et al., 2006]. To study the effects of electromagnetic ion cyclotron wave propagation and refraction on the wave induced ring current precipitation and heating of the thermal plasmaspheric electrons, we simulate the May 1998 storm. The main findings after a simulation can be summarized as follows. Firstly, the wave induced ring current precipitation exhibits quite a lot of fine structure, and is highly organized by location of the plasmapause gradient. The strongest fluxes of about 4 x 10(exp 6) (cm(raised dot) s(raised dot) sr(raised dot) (sup -1)) are observed during the maill and early recovery phases of the storm. The very interesting and probably more important finding is that in a number of cases the most intense precipitating fluxes are not connected to the most intense waves in simple manner. The characteristics of the wave power spectral density distribution over the wave normal angle are extremely crucial for the effectiveness of the ring current ion scattering. Secondly, comparison of the global proton precipitating patterns with the results from RAM [Kozyra et al., 1997a] reveals that although we observe a qualitative agreement between the localizations of the wave induced precipitations in the models, there is no quantitative agreement between the magnitudes of the fluxes. The quantitative differences are mainly due to a qualitative difference between the characteristics of the wave power spectral density distributions over the wave normal angle in RAM and in our model. Thirdly, the heat fluxes to plasmaspheric electrons caused by Landau resonate energy absorption from electromagnetic ion cyclotron waves are observed in the postnoon-premidnight MLT sector, and can reach the magnitude of 10(exp 11) eV/(cm(sup 2)(raised dot)s). The Coulomb energy degradation of the RC H(+) and O(+) ions maximizes at about 10(exp 11) (eV/(cm(sup 2) (raised dot) s), and typically leads to electron energy deposition rates of about 2(raised dot) 10(exp 10) (eV/(cm(sup 2)(raised dot)s) which are observed during two periods; 32-48 hours, and 76-86 hours after 1 May, 0000 UT. The theoretically derived spatial structure of the thermal electron heating caused by interaction of the ring current with the plasmasphere is strongly supported by concurrent and conjugate plasma measurements from the plasmasphere, ring current, and topside ionosphere [Gurgiolo et al., 2005]. Finally, the wave induced intense electron heating has a structure of the spot-like patches along the most enhanced density gradients in the plasmasphere boundary layer and can be a possible driver to the observed but still not explained small-scale structures of enhanced emissions in the stable auroral red arcs.

Self-Consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 2; Waves, Precipitating Ring Current Ions, and Thermal Electron Heating

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.

2006-01-01

This paper is dedicated to further presentations and discussions of the results from our new global self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves [Khazanov et al., 2006; here referred to as Paper 1]. In order to adequately take into account the wave propagation and refraction in a multi-ion plasmasphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation [for details see Paper 1]. To demonstrate the effects of the EMIC wave propagation and refraction on the RC proton precipitations and heating of the thermal plasmaspheric electrons we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. Firstly, the wave induced precipitations have a quite fine structure, and are highly organized by location of the plasmapause gradient. The strongest fluxes of about 4 (raised dot) 10(exp 6) [(cm (raised dot) s (raised dot) sr)(sup -l)] are observed during the main and early recovery phases of the storm. The very interesting and probably more important finding is that in a number of cases the most intense precipitating fluxes are not simply connected to the most intense EMIC waves. The character of the EMIC wave power spectral density distribution over the equatorial wave normal angle is an extremely crucial for the effectiveness of the RC ion scattering. Secondly, comparison of the global proton precipitating patterns with the results from other ring current model [Kozyra et al., 1997] reveals that although we observe a qualitative agreement between localizations of the wave induced fluxes in the models, there is no quantitative agreement between the magnitudes of these fluxes. These differences are mainly due to a qualitative difference between the characters of the EMIC wave power spectral density distributions over the equatorial wave normal angle. Finally, the two energy sources to the plasmaspheric electrons are considered; (i) the heat fluxes caused by the EMIC wave energy absorption due to Landau resonance, and (ii) the heat fluxes due to Coulomb energy degradation of the RC o(+) ions. The heat fluxes caused by the EMIC wave energy absorption due to Landau resonance are observed in the postnoon-premidnight MLT sector, and maximize at the magnitude of 10l1 (eV/(cm(sup 2)(raised dot) s) at L=3.25, MLT=22 at 3400 UT after 1 May, 0000 UT. The greatest Coulomb energy deposition rates are about 2 (raised dot) 10(sup 10)(eV/(cm(sup 2)(raised dot) s) and observed during two periods; 32-48 hours, and 76-86 hours after 1 May, 0000 UT. The theoretically derived spatial structure of the thermal electron heating caused by interaction of the RC with plasmasphere is strongly supported by concurrent and conjugate plasma measurements from the plasmasphere, the RC, and the topside ionosphere [Gurgiolo et al., 20051.

Local Electron Density Measurements from Sounding Experiments by RPI on IMAGE

NASA Astrophysics Data System (ADS)

Proddaturi, R.; Sonwalkar, V. S.; Li, J.; Venkatasubramanian, A.; Carpenter, D.; Benson, R.; Reinisch, B.

2004-12-01

RPI sounding experiments lead to a variety of echoes, propagating in various plasma wave modes, and local resonances. Characteristic frequencies of these echoes and resonances can be used to determine the local plasma frequency and thus the local electron density. In this work we have estimated plasma frequency by two methods: (1) using upper hybrid frequency measured from the diffuse Z mode echo upper cutoff and gyro-frequency measured from a gap in the diffuse Z mode echo or from resonances at the multiples of gyrofrequency, (2) upper hybrid frequency from the diffuse Z mode and the free space cutoff frequency fR=0 from the R-X mode echo. Broadband diffuse Z-mode echoes occur 90% of the time at high latitudes (λ m>45oS) near perigee in the southern hemisphere, where fpe << fce. In the middle and low latitudes (λ m<45oS), where fpe >> fce, Z-mode echoes are narrowband and are often accompanied by Qn and Dn resonances. The free space R-X mode echoes are commonly observed at both high and low latitudes. Multiples of gyrofrequency are typically observed at mid- to low-latitude in both the northern and southern hemisphere and at high latitude in the northern hemisphere. RPI plasmagrams were analyzed for three orbits (apogee to apogee) in the year 2002. These three orbits were selected because suitable sounding programs, those that can cover Z mode bandwidth over a wide range of latitude, were used, and also because a large number of diffuse Z mode echoes were actually observed. Electron densities as low as 10 el/cc and as high as 9000 el/cc were measured. The transmission frequencies place a limitation on the upper and lower limits of measurable fpe. The measured fpe values showed good agreement with measurements made from the thermal noise but showed large deviations when compared with model fpe values. For a particular orbit on August 26, 2002, Ne measured was as low as ˜20 el/cc at higher altitudes outside the plasmasphere (λ m > 60oN, altitude >7000 km, MLT=1.89) and increased as IMAGE approached the plasmasphere. A maximum of ˜8900 el/cc was measured well within the plasmasphere (L = 1.56, λ m = 17oN, altitude =2700 km, MLT = 2.44). As the satellite left the plasmasphere, measured electron density decreased to a minimum of about 55 el/cc near the auroral zone (L = 6.83, λ m = 57oS, altitude = 6277 km, MLT=13.66) and then started to rise again. A sharper change in Ne was seen at both the inbound and outbound crossings of the plasmapause. As the satellite again entered the plasmasphere (L = 3.94, λ m = 21oS, altitude = 15500 km, MLT = 14.34) at a higher altitude the maximum value of Ne measured was lower ( ˜520 el/cc) as expected. Our results demonstrate that magnetospheric sounding experiments employing Z mode and free space modes provide a powerful means of making local plasma density measurements.

Visualization of High Latitude Ion Upflow in Support of the Image Mission

NASA Technical Reports Server (NTRS)

Wilson, Gordon R.

1996-01-01

The study of the magnetosphere is a 400 year old science that began with the publication by Gilbert, in 1600, of his hypotheses that the Earth was a giant magnet. Since then we have learned many things about the magnetosphere, particularly in the last 40 years of the space age, but we still have many unanswered questions. In spite of the many thousands of observations of this system we still lack a global understanding of how it works. This is due to its large size and tenuous nature that mean that any measurement made of the fields or particles involved only give one a knowledge of the local conditions at a given time. To gain a global perspective through such observations would require the simultaneous operation of thousands of satellites spread throughout the magnetospheric system in addition to observations made on the ground. Such a program would be impractical at least from financial considerations. What is needed for the advancement of magnetospheric physics is to develop the same capabilities that astrophysicists, solar physicists and meteorologists have been using for years --- the ability to stand back from the object under study and see it in its entirety. The challenge for doing this for the magnetosphere is that the particle densities are very low and the material is, for the most part, not luminous. In the last 25 years several ideas have been proposed that would allow at least the imaging of certain portions of the magnetosphere. These include imaging of the plasmasphere through the resonant scattering of solar 304 A from He+ ions, imaging of various hot plasma populations (i.e. the ring current, plasmasheet, upflowing ionospheric ions, etc.) from the neutral atoms that result when ions of these populations charge exchange with the hydrogen geocorona, and imaging the aurora at various wavelengths in the far ultraviolet. In addition, a novel technique for probing various boundaries in the magnetosphere by bouncing low frequency radio waves off of them has been extensively studied. Such a technique is analogous to the way the under water world can be probed with sonar. About five years ago NASA convened a science working group to study the possibility of flying a magnetospheric imaging mission. This resulted in a number of proposals for such a mission, one of which was selected to be the first MIDEX mission, to be launched in early 2000. The mission is called IMAGE (Imager for Magnetopause to Aurora Global Exploration) and its P.I. is J. Burch at SwRI. The IMAGE spacecraft will carry imagers to view the plasmasphere, aurora, ring current, inner plasmasheet, and upflowing ionospheric ions as well as a radio sounder to probe the location, shape and dynamics of the magnetopause, plasmapause, etc. Between its selection last April and the non advocacy mission review, which takes place next spring, the IMAGE teams needs to further refine the design of the mission and its instruments. The theory and modeling (T&M) subgroup of this team has the task of demonstrating what kind of images the instruments on IMAGE will see as well as showing that useful scientific information can be extracted from such images. As a central element to the efforts of the T&M subgroup we have decided to simulate and create synthetic images for the magnetic cloud event of October, 1995. In this event a large cloud, with high plasma densities and strong magnetic fields, ejected from the sun collided with the earth's magnetosphere triggering a three day period of intense magnetic storms and substorms. This event was observed from a number of different spacecraft and on the ground so we have a good data set to work with. In our work we will place the IMAGE spacecraft in the magnetosphere on its proposed orbit, with its proposed instruments, to see what it would see had it been there. Existing models of the plasmasphere, ring current and magnetopause will be run for this event to give the structures for the imaging instruments. There are several models which are lacking and which need to be developed. These include a model for the cusp, the inner plasmasheet and the upflowing ions. My task this summer was to develop the upflowing ion model and use it to create synthetic images.