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Found 2758 entries in the Bibliography.
Showing entries from 551 through 600
| 2019 |
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The magnetospheric driver of strong thermal emission velocity enhancement (STEVE) is investigated using conjugate observations when Van Allen Probes\textquoteright footprint directly crossed both STEVE and stable red aurora (SAR) arc. In the ionosphere, STEVE is associated with subauroral ion drift features, including electron temperature peak, density gradient, and westward ion flow. The SAR arc at lower latitudes corresponds to regions inside the plasmapause with isotropic plasma heating, which causes redline-only SAR emission via heat conduction. STEVE corresponds to the sharp plasmapause boundary containing quasi-static subauroral ion drift electric field and parallel-accelerated electrons by kinetic Alfv\ en waves. These parallel electrons could precipitate and be accelerated via auroral acceleration processes powered by Alfv\ en waves propagating along the magnetic field with the plasmapause as a waveguide. The electron precipitation, superimposed on the heat conduction, could explain multiwavelength continuous STEVE emission. The green picket-fence emissions are likely optical manifestations of electron precipitation associated with wave structures traveling along the plasmapause. Chu, Xiangning; Malaspina, David; Gallardo-Lacourt, Bea; Liang, Jun; Andersson, Laila; Ma, Qianli; Artemyev, Anton; Liu, Jiang; Ergun, Robert; Thaller, Scott; Akbari, Hassanali; Zhao, Hong; Larsen, Brian; Reeves, Geoffrey; Wygant, John; Breneman, Aaron; Tian, Sheng; Connors, Martin; Donovan, Eric; Archer, William; MacDonald, Elizabeth; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL082789 aurora; kinetic Alfven wave; Plasmapause; STEVE; subauroral ion drift; table red auroral arc; Van Allen Probes |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures \textquotedblleftremotely,\textquotedblright whereas RBSP-B observed them \textquotedblleftlocally.\textquotedblright Teramoto, M.; Hori, T.; Saito, S.; Miyoshi, Y.; Kurita, S.; Higashio, N.; Matsuoka, A.; Kasahara, Y.; Kasaba, Y.; Takashima, T.; Nomura, R.; e, Nos\; Fujimoto, A.; Tanaka, Y.-M.; Shoji, M.; Tsugawa, Y.; Shinohara, M.; Shinohara, I.; Blake, J.; Fennell, J.F.; Claudepierre, S.G.; Turner, D.; Kletzing, C.; Sormakov, D.; Troshichev, O.; Published by: Geophysical Research Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019GL084379 |
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Storm Time Depletions of Multi-MeV Radiation Belt Electrons Observed at Different Pitch Angles During geomagnetic storms, the rapid depletion of the high-energy (several MeV) outer radiation belt electrons is the result of loss to the interplanetary medium through the magnetopause, outward radial diffusion, and loss to the atmosphere due to wave-particle interactions. We have performed a statistical study of 110 storms using pitch angle resolved electron flux measurements from the Van Allen Probes mission and found that inside of the radiation belt (L* = 3 - 5) the number of storms that result in depletion of electrons with equatorial pitch angle αeq = 30o is higher than number of storms that result in depletion of electrons with equatorial pitch angle αeq = 75o. We conclude that this result is consistent with electron scattering by whistler and electromagnetic ion cyclotron waves. At the outer edge of the radiation belt (L* >= 5.2) the number of storms that result in depletion is also large (~40\textendash50\%), emphasizing the significance of the magnetopause shadowing effect and outward radial transport. Drozdov, A; Aseev, N.; Effenberger, F.; Turner, D.; Saikin, A.; Shprits, Y; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2019 YEAR: 2019 DOI: 10.1029/2019JA027332 EMIC waves; multi-MeV electrons; Radiation belts; Van Allen Probes |
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Using energetic particle and wave measurements from the Van Allen Probes, Polar Orbiting Environmental Satellites (POES), and Geostationary Operational Environmental Satellite (GOES), the acceleration mechanism of ultrarelativistic electrons (>3 MeV) in the center of the outer radiation belt is investigated statistically. A superposed epoch analysis is conducted using 19 storms, which caused flux enhancements of 1.8\textendash7.7 MeV electrons. The evolution of electron phase space density radial profile suggests an energy-dependent acceleration of ultrarelativistic electrons in the outer belt. Especially, for electrons with very high energies (~7 MeV), prevalent positive phase space density radial gradients support inward radial diffusion being responsible for electron acceleration in the center of the outer belt (L*~3\textendash5) during most enhancement events in the Van Allen Probes era. We propose a two-step acceleration process to explain the acceleration of ~7 MeV electrons in the outer belt: intense and sustained chorus waves locally energize core electron populations to ultrarelativistic energies at high L region beyond the Van Allen Probes\textquoteright apogee, followed by inward radial diffusion which further energizes these populations to even higher energies. Statistical results of chorus wave activity inferred from POES precipitating electron measurements as well as core electron populations observed by the Van Allen Probes and GOES support this hypothesis. Zhao, H.; Baker, D.N.; Li, X.; Malaspina, D.M.; Jaynes, A.N.; Kanekal, S.G.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA027111 Acceleration mechanism; Inward radial diffusion; Local Acceleration; Phase space density; Radiation belts; ultrarelativistic electrons; Van Allen Probes |
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Characteristics and Generation of Low-Frequency Magnetosonic Waves Below the Proton Gyrofrequency We report a Van Allen Probes observation of large-amplitude magnetosonic waves with the peak intensity below the proton gyrofrequency (fcp), which may potentially be misinterpreted as electromagnetic ion cyclotron waves. The frequency spacing of the wave harmonic structure suggests that these magnetosonic waves are excited at a distant source region and propagate radially inward. We also conduct a statistical analysis of low-frequency magnetosonic waves below fcp based on the Van Allen Probes data from October 2012 to December 2018. The spatial distribution shows that these low-frequency magnetosonic emissions are dominantly observed inside the plasmasphere from the prenoon to the midnight sector within 5\textdegree of the geomagnetic equator and typically have modest-to-strong wave amplitudes ranging from tens of pT to hundreds of pT. Our study provides insight into understanding the generation and propagation of these low-frequency magnetosonic waves in the Earth\textquoterights inner magnetosphere. Teng, Shangchun; Li, Wen; Tao, Xin; Ma, Qianli; Shen, Xiaochen; Published by: Geophysical Research Letters Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019GL085372 Below the proton gyrofrequency; Low frequency magnetosonic wave; Van Allen Probes; wave generation; Wave propagation characteristics |
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Six years of Van Allen Probes data are used to investigate cold plasmaspheric electrons affected by ultralow-frequency (ULF) waves in the inner magnetosphere (L<7) including spatial distributions, occurrence conditions, and resonant energy range. Events exhibit a global distribution within L= 4\textendash7 but preferentially occur at L\~5.5\textendash7 in the dayside, while there is higher occurrence rate in the duskside than dawnside. They can occur under different geomagnetic activities and solar wind velocities (VS), but the occurrence rates are increasing with larger AE, |SYMH|, and VS. These features are closely associated with the generation and propagation of ULF waves in Pc4 (45\textendash150 s) and Pc5 (150\textendash600 s) bands. Combined with electron observations from HOPE instrument, the resonant energies inferred from wave power indicate that cold electrons at ones to hundreds of electron volts can be affected by ULF waves. This study may shed new light on further investigations on the acceleration and transportation of cold plasmaspheric particles that would affect plasmaspheric material release to the Earth\textquoterights magnetosphere and instabilities for exciting various waves. Ren, Jie; Zong, Q.; Zhou, X.; Spence, H.; Funsten, H.; Wygant, J.; Rankin, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA027009 Cold plasmaspheric electrons; drift-bounce resonance; ULF waves; Van Allen Probes; Wave-particle interaction |
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Six years of Van Allen Probes data are used to investigate cold plasmaspheric electrons affected by ultralow-frequency (ULF) waves in the inner magnetosphere (L<7) including spatial distributions, occurrence conditions, and resonant energy range. Events exhibit a global distribution within L= 4\textendash7 but preferentially occur at L\~5.5\textendash7 in the dayside, while there is higher occurrence rate in the duskside than dawnside. They can occur under different geomagnetic activities and solar wind velocities (VS), but the occurrence rates are increasing with larger AE, |SYMH|, and VS. These features are closely associated with the generation and propagation of ULF waves in Pc4 (45\textendash150 s) and Pc5 (150\textendash600 s) bands. Combined with electron observations from HOPE instrument, the resonant energies inferred from wave power indicate that cold electrons at ones to hundreds of electron volts can be affected by ULF waves. This study may shed new light on further investigations on the acceleration and transportation of cold plasmaspheric particles that would affect plasmaspheric material release to the Earth\textquoterights magnetosphere and instabilities for exciting various waves. Ren, Jie; Zong, Q.; Zhou, X.; Spence, H.; Funsten, H.; Wygant, J.; Rankin, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA027009 Cold plasmaspheric electrons; drift-bounce resonance; ULF waves; Van Allen Probes; Wave-particle interaction |
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Propagation of EMIC Waves Inside the Plasmasphere: A Two-Event Study Electromagnetic ion cyclotron (EMIC) waves are important for the loss of high-energy electrons in the radiation belt. Based on the measurements of Van Allen Probes, two events during the same storm period are presented to study the propagation of EMIC waves. In the first event, left-handed polarized EMIC waves were observed near the plasmapause, while right-handed waves were observed in the inner plasmasphere. The Poynting flux of the right-hand waves was mainly directed inward and equatorward, and no positive growth rates were obtained in the region of these right-hand waves, indicating the inward propagation of the waves from a higher L-shell. In the second event, the wave vectors were quasi-perpendicular to the background magnetic field inside the plasmaspheric plume but became quasi-parallel outside. This phenomenon can be explained by the refraction of the large density gradient, which qualitatively satisfies Snell\textquoterights law. These observations provide indirect evidence of the inward propagation of the EMIC waves and give a new insight on how density gradients may modify wave properties Wang, G.; Zhang, T.; Gao, Z.; Wu, M; Wang, G.; Schmid, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA027055 density gradient; EMIC wave; inward propagation; refraction; right hand polarization; Snell\textquoterights law; Van Allen Probes |
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RBSP-ECT Combined Spin-Averaged Electron Flux Data Product We describe a new data product combining the spin-averaged electron flux measurements from the Radiation Belt Storm Probes (RBSP) Energetic Particle Composition and Thermal Plasma (ECT) suite on the National Aeronautics and Space Administration\textquoterights Van Allen Probes. We describe the methodology used to combine each of the data sets and produce a consistent set of spectra for September 2013 to the present. Three-minute-averaged flux spectra are provided spanning energies from 15 eV up to 20 MeV. This new data product provides additional utility to the ECT data and offers a consistent cross calibrated data set for researchers interested in examining the dynamics of the inner magnetosphere across a wide range of energies. Boyd, A.; Reeves, G.; Spence, H.; Funsten, H.; Larsen, B.; Skoug, R.; Blake, J.; Fennell, J.; Claudepierre, S.; Baker, D.; Kanekal, S.; Jaynes, A.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA026733 |
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RBSP-ECT Combined Spin-Averaged Electron Flux Data Product We describe a new data product combining the spin-averaged electron flux measurements from the Radiation Belt Storm Probes (RBSP) Energetic Particle Composition and Thermal Plasma (ECT) suite on the National Aeronautics and Space Administration\textquoterights Van Allen Probes. We describe the methodology used to combine each of the data sets and produce a consistent set of spectra for September 2013 to the present. Three-minute-averaged flux spectra are provided spanning energies from 15 eV up to 20 MeV. This new data product provides additional utility to the ECT data and offers a consistent cross calibrated data set for researchers interested in examining the dynamics of the inner magnetosphere across a wide range of energies. Boyd, A.; Reeves, G.; Spence, H.; Funsten, H.; Larsen, B.; Skoug, R.; Blake, J.; Fennell, J.; Claudepierre, S.; Baker, D.; Kanekal, S.; Jaynes, A.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA026733 |
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Storm-time convection dynamics viewed from optical auroras A series of statistical and event studies have demonstrated that the motion of patches in regions of Patchy Pulsating Aurora (PPA) is very close to, if not exactly, convection. Therefore, 2D maps of PPA motion provide us the opportunity to remotely sense magnetospheric convection with relatively high space and time resolution, subject to uncertainties associated with the mapping between the ionosphere and magnetosphere. In this study, we use THEMIS ASI (All Sky Imager) aurora observations combined with RBSP electric field and magnetic field measurements to explore convection dynamics during storm time. From 0500 UT to 0600 UT on March 19 2015, auroral observations across ~4 h of magnetic local time (MLT) show that increases in the westward velocities of patches are closely related to earthward flow bursts in the inner plasma sheet. Together with the meridian scanning photometer (MSP) data, this suggests that the increase in the westward velocities of PPA patches is caused by earthward-moving ion injection structures carried by the fast earthward flows. Yang, Bing; Donovan, Eric; Liang, Jun; Ruohoniemi, Michael; McWilliams, Kathryn; Spanswick, Emma; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1016/j.jastp.2019.105088 Auroral streamer; convection; Fast earthward flows; pulsating aurora; Van Allen Probes |
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Storm-time convection dynamics viewed from optical auroras A series of statistical and event studies have demonstrated that the motion of patches in regions of Patchy Pulsating Aurora (PPA) is very close to, if not exactly, convection. Therefore, 2D maps of PPA motion provide us the opportunity to remotely sense magnetospheric convection with relatively high space and time resolution, subject to uncertainties associated with the mapping between the ionosphere and magnetosphere. In this study, we use THEMIS ASI (All Sky Imager) aurora observations combined with RBSP electric field and magnetic field measurements to explore convection dynamics during storm time. From 0500 UT to 0600 UT on March 19 2015, auroral observations across ~4 h of magnetic local time (MLT) show that increases in the westward velocities of patches are closely related to earthward flow bursts in the inner plasma sheet. Together with the meridian scanning photometer (MSP) data, this suggests that the increase in the westward velocities of PPA patches is caused by earthward-moving ion injection structures carried by the fast earthward flows. Yang, Bing; Donovan, Eric; Liang, Jun; Ruohoniemi, Michael; McWilliams, Kathryn; Spanswick, Emma; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1016/j.jastp.2019.105088 Auroral streamer; convection; Fast earthward flows; pulsating aurora; Van Allen Probes |
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The Storm-Time Ring Current Response to ICMEs and CIRs Using Van Allen Probe Observations Using Van Allen Probe observations of the inner magnetosphere during geomagnetic storms driven by interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs), we characterize the impact of these drivers on the storm-time ring current development. Using 25 ICME- and 35 CIR-driven storms, we have determined the ring current pressure development during the prestorm, main, early-recovery, and late-recovery storm phases, as a function of magnetic local time, L shell and ion species (H+, He+, and O+) over the 100- to 600-keV energy range. Consistent with previous results, we find that during the storm main phase, most of the ring current pressure in the inner magnetosphere is contributed by particles on open drift paths drifting duskward leading to a strong partial ring current. The largest difference between the ICME and CIR ring current responses during the storm main and early-recovery phases is the difference in the response of the <~55-keV O+ to these drivers. While the H+ pressure response shows similar source and convection patterns for ICME and CIR storms, the O+ pressure response is significantly stronger for ICME storms. The ICME O+ pressure increases more strongly than H+ with decreasing L and peaks at lower L shells than H+. Mouikis, C.; Bingham, S.; Kistler, L.; Farrugia, C.; Spence, H.; Reeves, G.; Gkioulidou, M.; Mitchell, D.; Kletzing, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA026695 ICME vs CI; R Ion composition; Ring Current Pressure; Storm phases; Van Allen Probes |
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The Storm-Time Ring Current Response to ICMEs and CIRs Using Van Allen Probe Observations Using Van Allen Probe observations of the inner magnetosphere during geomagnetic storms driven by interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs), we characterize the impact of these drivers on the storm-time ring current development. Using 25 ICME- and 35 CIR-driven storms, we have determined the ring current pressure development during the prestorm, main, early-recovery, and late-recovery storm phases, as a function of magnetic local time, L shell and ion species (H+, He+, and O+) over the 100- to 600-keV energy range. Consistent with previous results, we find that during the storm main phase, most of the ring current pressure in the inner magnetosphere is contributed by particles on open drift paths drifting duskward leading to a strong partial ring current. The largest difference between the ICME and CIR ring current responses during the storm main and early-recovery phases is the difference in the response of the <~55-keV O+ to these drivers. While the H+ pressure response shows similar source and convection patterns for ICME and CIR storms, the O+ pressure response is significantly stronger for ICME storms. The ICME O+ pressure increases more strongly than H+ with decreasing L and peaks at lower L shells than H+. Mouikis, C.; Bingham, S.; Kistler, L.; Farrugia, C.; Spence, H.; Reeves, G.; Gkioulidou, M.; Mitchell, D.; Kletzing, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA026695 ICME vs CI; R Ion composition; Ring Current Pressure; Storm phases; Van Allen Probes |
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Variability of Quasilinear Diffusion Coefficients for Plasmaspheric Hiss In the outer radiation belt, the acceleration and loss of high-energy electrons is largely controlled by wave-particle interactions. Quasilinear diffusion coefficients are an efficient way to capture the small-scale physics of wave-particle interactions due to magnetospheric wave modes such as plasmaspheric hiss. The strength of quasilinear diffusion coefficients as a function of energy and pitch angle depends on both wave parameters and plasma parameters such as ambient magnetic field strength, plasma number density, and composition. For plasmaspheric hiss in the magnetosphere, observations indicate large variations in the wave intensity and wave normal angle, but less is known about the simultaneous variability of the magnetic field and number density. We use in situ measurements from the Van Allen Probe mission to demonstrate the variability of selected factors that control the size and shape of pitch angle diffusion coefficients: wave intensity, magnetic field strength, and electron number density. We then compare with the variability of diffusion coefficients calculated individually from colocated and simultaneous groups of measurements. We show that the distribution of the plasmaspheric hiss diffusion coefficients is highly non-Gaussian with large variance and that the distributions themselves vary strongly across the three phase space bins studied. In most bins studied, the plasmaspheric hiss diffusion coefficients tend to increase with geomagnetic activity, but our results indicate that new approaches that include natural variability may yield improved parameterizations. We suggest methods like stochastic parameterization of wave-particle interactions could use variability information to improve modeling of the outer radiation belt. Watt, C.; Allison, H.; Meredith, N.; Thompson, R.; Bentley, S.; Rae, I.; Glauert, S.; Horne, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2018JA026401 empirical; Magnetosphere; parameterization; stochastic; Van Allen Probes; wave-particle interactions |
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Variability of Quasilinear Diffusion Coefficients for Plasmaspheric Hiss In the outer radiation belt, the acceleration and loss of high-energy electrons is largely controlled by wave-particle interactions. Quasilinear diffusion coefficients are an efficient way to capture the small-scale physics of wave-particle interactions due to magnetospheric wave modes such as plasmaspheric hiss. The strength of quasilinear diffusion coefficients as a function of energy and pitch angle depends on both wave parameters and plasma parameters such as ambient magnetic field strength, plasma number density, and composition. For plasmaspheric hiss in the magnetosphere, observations indicate large variations in the wave intensity and wave normal angle, but less is known about the simultaneous variability of the magnetic field and number density. We use in situ measurements from the Van Allen Probe mission to demonstrate the variability of selected factors that control the size and shape of pitch angle diffusion coefficients: wave intensity, magnetic field strength, and electron number density. We then compare with the variability of diffusion coefficients calculated individually from colocated and simultaneous groups of measurements. We show that the distribution of the plasmaspheric hiss diffusion coefficients is highly non-Gaussian with large variance and that the distributions themselves vary strongly across the three phase space bins studied. In most bins studied, the plasmaspheric hiss diffusion coefficients tend to increase with geomagnetic activity, but our results indicate that new approaches that include natural variability may yield improved parameterizations. We suggest methods like stochastic parameterization of wave-particle interactions could use variability information to improve modeling of the outer radiation belt. Watt, C.; Allison, H.; Meredith, N.; Thompson, R.; Bentley, S.; Rae, I.; Glauert, S.; Horne, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2018JA026401 empirical; Magnetosphere; parameterization; stochastic; Van Allen Probes; wave-particle interactions |
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Variability of Quasilinear Diffusion Coefficients for Plasmaspheric Hiss In the outer radiation belt, the acceleration and loss of high-energy electrons is largely controlled by wave-particle interactions. Quasilinear diffusion coefficients are an efficient way to capture the small-scale physics of wave-particle interactions due to magnetospheric wave modes such as plasmaspheric hiss. The strength of quasilinear diffusion coefficients as a function of energy and pitch angle depends on both wave parameters and plasma parameters such as ambient magnetic field strength, plasma number density, and composition. For plasmaspheric hiss in the magnetosphere, observations indicate large variations in the wave intensity and wave normal angle, but less is known about the simultaneous variability of the magnetic field and number density. We use in situ measurements from the Van Allen Probe mission to demonstrate the variability of selected factors that control the size and shape of pitch angle diffusion coefficients: wave intensity, magnetic field strength, and electron number density. We then compare with the variability of diffusion coefficients calculated individually from colocated and simultaneous groups of measurements. We show that the distribution of the plasmaspheric hiss diffusion coefficients is highly non-Gaussian with large variance and that the distributions themselves vary strongly across the three phase space bins studied. In most bins studied, the plasmaspheric hiss diffusion coefficients tend to increase with geomagnetic activity, but our results indicate that new approaches that include natural variability may yield improved parameterizations. We suggest methods like stochastic parameterization of wave-particle interactions could use variability information to improve modeling of the outer radiation belt. Watt, C.; Allison, H.; Meredith, N.; Thompson, R.; Bentley, S.; Rae, I.; Glauert, S.; Horne, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2018JA026401 empirical; Magnetosphere; parameterization; stochastic; Van Allen Probes; wave-particle interactions |
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Electrons with energies in the keV range play an important role in the dynamics of the inner magnetosphere. Therefore, accurately modeling electron fluxes in this region is of great interest. However, these calculations constitute a challenging task since the lifetimes of electrons that are available have limitations. In this study, we simulate electron fluxes in the energy range of 20 eV to 100 keV to assess how well different electron loss models can account for the observed electron fluxes during the Geospace Environment Modelling Challenge Event of the 2013 St. Patrick\textquoterights Day storm. Three models (Case 1, Case 2, and Case 3) of electron lifetimes due to wave-induced pitch angle scattering are used to compute the fluxes, which are compared with measurements from the Van Allen Probes. The three models consider electron losses due to interactions with whistler mode hiss waves inside the plasmasphere and with whistler mode chorus waves outside the plasmasphere. The Case 1 (historical) model produces excessive loss at low L shells before and after the storm, suggesting that it overestimates losses due to hiss during quiet times. During the storm main phase and early recovery all three models show good agreement with the observations, indicating that losses due to chorus during disturbed times are, in general, well accounted for by the models. Furthermore, the more recent Case 2 and Case 3 models show overall better agreement with the observed fluxes. Ferradas, C.; Jordanova, V.; Reeves, G.; Larsen, B.; Published by: Journal of Geophysical Research: Space Physics Published on: 09/2019 YEAR: 2019 DOI: 10.1029/2019JA026649 electron lifetime; electron loss; numerical modeling; pitch angle scattering; Van Allen Probes; Weimer electric field model |
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We use the UNH-IMEF, Weimer 1996, https://doi.org/10.1029/96GL02255 and Volland-Stern electric field models along with a dipole magnetic field to calculate drift paths for particles that reach the Van Allen Probes\textquoteright orbit for two inbound passes during two large geomagnetic storms. We compare the particle access in the models with the observed particle access using both realistic and enhanced solar wind model parameters. To test the accuracy of the drift paths, we estimate the H+ charge exchange loss along these drift paths. While increasing the strength of the model electric field drives particles further inward, improving agreement, energy-dependent cutoffs in the spectra do not agree, indicating that potential patterns for highly disturbed times are inaccurate. While none of the models were able to reproduce the observed features of the more dawnward pass during the 17 March 2013 storm, the UNH-IMEF model with enhanced inputs was able to adequately reproduce the access, charge exchange loss, and H+ particle pressure during the 17 March 2015 storm. Menz, A.M.; Kistler, L.M.; Mouikis, C.G.; Matsui, H.; Spence, H.E.; Thaller, S.A.; Wygant, J.R.; Published by: Journal of Geophysical Research: Space Physics Published on: 09/2019 YEAR: 2019 DOI: 10.1029/2019JA026683 |
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Analyzing EMIC Waves in the Inner Magnetosphere Using Long-Term Van Allen Probes Observations With 64-month magnetic data from Van Allen Probes, we have studied not only the global distribution, wave normal angle (θ), and ellipticity (ε) of electromagnetic ion cyclotron (EMIC) waves, but also the dependence of their occurrence rates and magnetic amplitudes on the AE* index (the mean value of AE index over previous 1 hr). Our results show that H+ band waves are preferentially detected at 5 <= L <= 6.5, in the noon sector. They typically have small θ (<30\textdegree) and weakly left-hand polarization but become more oblique and linearly polarized at larger magnetic latitudes or L-shells. With the increase of AE* index, their occurrence rate significantly increases in the noon sector, and their source region extends to dusk sector. He+ band waves usually occur in the predawn and morning sectors at 3 <= L <= 4.5. They generally have moderate θ (30 \textdegree - 40\textdegree) and left-hand polarization and also become more oblique and linearly polarized at larger latitudes or L-shells. There is a clear enhancement of occurrence rate and amplitude during active geomagnetic periods, especially in the dusk and evening sectors. O+ band waves mainly occur at 3 <= L <= 4 in the predawn sector. They have either very small θ (<20\textdegree) or very large θ (>50\textdegree), and typically linear or weakly right-hand polarization. During active periods, they mostly occur at the midnight sector and L < 3.5. As a valuable supplement to previous statistical studies, our result provides not only a more compresentive EMIC wave model for evaluating their effects on the radiation belt, but also detailed observational constraints on generation mechanisms of EMIC waves. Chen, Huayue; Gao, Xinliang; Lu, Quanming; Wang, Shui; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2019 YEAR: 2019 DOI: 10.1029/2019JA026965 A long-term statistical work; EMIC wave; inner magnetosphere; spatial distribution; Van Allen Probes; Van Allen Probes observation; Wave fundamental characters |
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The Van Allen Probes have observed both symmetric and asymmetric bipolar electric field structures in the Earth\textquoterights inner magnetosphere. In general, the symmetric bipolar structures are identified as electron-phase space holes, whereas the asymmetric structures are interpreted as electron acoustic double layers (EADLs). The generation mechanism of these EADLs is not entirely understood yet. We have modeled the EADLs observed on 13 November 2012 by Van Allen Probe-B. We performed a fluid simulation of the EADLs and tracked their formation and evolution in the simulation. We found that the localized depletion and enhancement in the electron populations act as a perturbation to excite the symmetric bipolar electron acoustic solitary waves, which later evolve into the EADLs. The Ponderomotive force is found to be the main driver behind transformation of the symmetric electron acoustic solitary waves to EADLs via formation of the electron acoustic shocks. Lotekar, Ajay; Kakad, Amar; Kakad, Bharati; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2019 YEAR: 2019 DOI: 10.1029/2018JA026303 Asymmetric electron acoustic double layers; Electron acoustic shock; Electrostatic solitary wave; Fluid simulation; Van Allen Probes |
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Substorm-Ring Current Coupling: A Comparison of Isolated and Compound Substorms Substorms are a highly variable process, which can occur as an isolated event or as part of a sequence of multiple substorms (compound substorms). In this study we identify how the low-energy population of the ring current and subsequent energization varies for isolated substorms compared to the first substorm of a compound event. Using observations of H+ and O+ ions (1 eV to 50 keV) from the Helium Oxygen Proton Electron instrument onboard Van Allen Probe A, we determine the energy content of the ring current in L-MLT space. We observe that the ring current energy content is significantly enhanced during compound substorms as compared to isolated substorms by \~20\textendash30\%. Furthermore, we observe a significantly larger magnitude of energization (by \~40\textendash50\%) following the onset of compound substorms relative to isolated substorms. Analysis suggests that the differences predominantly arise due to a sustained enhancement in dayside driving associated with compound substorms compared to isolated substorms. The strong solar wind driving prior to onset results in important differences in the time history of the magnetosphere, generating significantly different ring current conditions and responses to substorms. The observations reveal information about the substorm injected population and the transport of the plasma in the inner magnetosphere. Sandhu, J.; Rae, I.; Freeman, M.; Gkioulidou, M.; Forsyth, C.; Reeves, G.; Murphy, K.; Walach, M.-T.; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2019 YEAR: 2019 DOI: 10.1029/2019JA026766 inner magnetosphere; ring current; substorms; Van Allen; Van Allen Probes |
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Substorm-Ring Current Coupling: A Comparison of Isolated and Compound Substorms Substorms are a highly variable process, which can occur as an isolated event or as part of a sequence of multiple substorms (compound substorms). In this study we identify how the low-energy population of the ring current and subsequent energization varies for isolated substorms compared to the first substorm of a compound event. Using observations of H+ and O+ ions (1 eV to 50 keV) from the Helium Oxygen Proton Electron instrument onboard Van Allen Probe A, we determine the energy content of the ring current in L-MLT space. We observe that the ring current energy content is significantly enhanced during compound substorms as compared to isolated substorms by \~20\textendash30\%. Furthermore, we observe a significantly larger magnitude of energization (by \~40\textendash50\%) following the onset of compound substorms relative to isolated substorms. Analysis suggests that the differences predominantly arise due to a sustained enhancement in dayside driving associated with compound substorms compared to isolated substorms. The strong solar wind driving prior to onset results in important differences in the time history of the magnetosphere, generating significantly different ring current conditions and responses to substorms. The observations reveal information about the substorm injected population and the transport of the plasma in the inner magnetosphere. Sandhu, J.; Rae, I.; Freeman, M.; Gkioulidou, M.; Forsyth, C.; Reeves, G.; Murphy, K.; Walach, M.-T.; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2019 YEAR: 2019 DOI: 10.1029/2019JA026766 inner magnetosphere; ring current; substorms; Van Allen; Van Allen Probes |
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Empirical Modeling of the Geomagnetosphere for SIR and CME-Driven Magnetic Storms During geomagnetic disturbances, the solar wind arrives in the form of characteristic sequences lasting from tens of hours to days. The most important magnetic storm drivers are the coronal mass ejections (CMEs) and the slow-fast stream interaction regions (SIRs). Previous data-based magnetic field models did not distinguish between these types of the solar wind driving. In the present work we retained the basic structure of the Tsyganenko and Andreeva (2015) model but fitted it to data samples corresponding to (1) SIR-driven storms, (2) CME-driven storms preceded with a shock ahead of the CME, and (3) CME-driven storms without such shocks. The storm time dynamics of the model current systems has been represented using the parametrization method developed by Tsyganenko and Sitnov (2005), based on dynamical variables Wi, calculated from concurrent solar wind characteristics and their previous history. The database included observations of THEMIS, Polar, Cluster, Geotail, and Van Allen Probes missions during 155 storms in 1997\textendash2016. The model current systems drastically differ from each other with respect to decay rate and total current magnitudes. During SIR-induced storms, all current systems saturate, while during CME-induced disturbances, the saturation occurs only for the symmetric ring current and the tail current. The partial ring current parameters are drastically different between SIR- and CME-induced storm sets. In the case of SIR-driven storms, the total partial ring current is comparable with symmetric ring current, whereas for all CME-induced events it is nearly twice higher. The results are compared with GOES 15 magnetometer observations. Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2018JA026008 Magnetic Storms; Magnetosphere; Modeling; Solar wind; spacecraft data; Van Allen Probes |
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Auroral kilometric radiation (AKR) can potentially produce serious damage to space-borne systems by accelerating trapped radiation belt electrons to relativistic energies. Here we examine the global occurrences of AKR emissions in radiation belts based on Van Allen Probes observations from 1 October 2012 to 31 December 2016. The statistical results (1,848 events in total) show that AKR covers a broad region of L= 3\textendash6.5 and 00\textendash24 magnetic local time (MLT), with a higher occurrence on the nightside (20\textendash24 MLT and 00\textendash04 MLT) within L= 5\textendash6.5. All the AKR events are observed to be accompanied with suprathermal (\~1 keV) electron flux enhancements. During active geomagnetic periods, both AKR occurrences and electron injections tend to be more distinct, and AKR emission extends to the dayside. The current study shows that AKR emissions from the remote sources are closely associated with electron injections. Zhao, Wanli; Liu, Si; Zhang, Sai; Zhou, Qinghua; Yang, Chang; He, Yihua; Gao, Zhonglei; Xiao, Fuliang; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083944 Auroral kilometric radiation; global occurrence; Radiation belt; suprathermal electron flux enhancenments; Van Allen Probes |
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Auroral kilometric radiation (AKR) can potentially produce serious damage to space-borne systems by accelerating trapped radiation belt electrons to relativistic energies. Here we examine the global occurrences of AKR emissions in radiation belts based on Van Allen Probes observations from 1 October 2012 to 31 December 2016. The statistical results (1,848 events in total) show that AKR covers a broad region of L= 3\textendash6.5 and 00\textendash24 magnetic local time (MLT), with a higher occurrence on the nightside (20\textendash24 MLT and 00\textendash04 MLT) within L= 5\textendash6.5. All the AKR events are observed to be accompanied with suprathermal (\~1 keV) electron flux enhancements. During active geomagnetic periods, both AKR occurrences and electron injections tend to be more distinct, and AKR emission extends to the dayside. The current study shows that AKR emissions from the remote sources are closely associated with electron injections. Zhao, Wanli; Liu, Si; Zhang, Sai; Zhou, Qinghua; Yang, Chang; He, Yihua; Gao, Zhonglei; Xiao, Fuliang; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083944 Auroral kilometric radiation; global occurrence; Radiation belt; suprathermal electron flux enhancenments; Van Allen Probes |
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Auroral kilometric radiation (AKR) can potentially produce serious damage to space-borne systems by accelerating trapped radiation belt electrons to relativistic energies. Here we examine the global occurrences of AKR emissions in radiation belts based on Van Allen Probes observations from 1 October 2012 to 31 December 2016. The statistical results (1,848 events in total) show that AKR covers a broad region of L= 3\textendash6.5 and 00\textendash24 magnetic local time (MLT), with a higher occurrence on the nightside (20\textendash24 MLT and 00\textendash04 MLT) within L= 5\textendash6.5. All the AKR events are observed to be accompanied with suprathermal (\~1 keV) electron flux enhancements. During active geomagnetic periods, both AKR occurrences and electron injections tend to be more distinct, and AKR emission extends to the dayside. The current study shows that AKR emissions from the remote sources are closely associated with electron injections. Zhao, Wanli; Liu, Si; Zhang, Sai; Zhou, Qinghua; Yang, Chang; He, Yihua; Gao, Zhonglei; Xiao, Fuliang; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083944 Auroral kilometric radiation; global occurrence; Radiation belt; suprathermal electron flux enhancenments; Van Allen Probes |
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Auroral kilometric radiation (AKR) can potentially produce serious damage to space-borne systems by accelerating trapped radiation belt electrons to relativistic energies. Here we examine the global occurrences of AKR emissions in radiation belts based on Van Allen Probes observations from 1 October 2012 to 31 December 2016. The statistical results (1,848 events in total) show that AKR covers a broad region of L= 3\textendash6.5 and 00\textendash24 magnetic local time (MLT), with a higher occurrence on the nightside (20\textendash24 MLT and 00\textendash04 MLT) within L= 5\textendash6.5. All the AKR events are observed to be accompanied with suprathermal (\~1 keV) electron flux enhancements. During active geomagnetic periods, both AKR occurrences and electron injections tend to be more distinct, and AKR emission extends to the dayside. The current study shows that AKR emissions from the remote sources are closely associated with electron injections. Zhao, Wanli; Liu, Si; Zhang, Sai; Zhou, Qinghua; Yang, Chang; He, Yihua; Gao, Zhonglei; Xiao, Fuliang; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083944 Auroral kilometric radiation; global occurrence; Radiation belt; suprathermal electron flux enhancenments; Van Allen Probes |
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Lightning Contribution to Overall Whistler Mode Wave Intensities in the Plasmasphere Electromagnetic waves generated by lightning propagate into the plasmasphere as dispersed whistlers. They can therefore influence the overall wave intensity in space, which, in turn, is important for dynamics of the Van Allen radiation belts. We analyze spacecraft measurements in low-Earth orbit as well as in high-altitude equatorial region, together with a ground-based estimate of lightning activity. We accumulate wave intensities when the spacecraft are magnetically connected to thunderstorms and compare them with measurements obtained when thunderstorms are absent. We show that strong lightning activity substantially affects the wave intensity in a wide range of L-shells and altitudes. The effect is observed mainly between 500 Hz and 4 kHz, but its frequency range strongly varies with L-shell, extending up to 12 kHz for L lower than 3. The effect is stronger in the afternoon, evening, and night sectors, consistent with more lightning and easier wave propagation through the ionosphere. ahlava, J.; emec, F.; Santolik, O.; a, Kolma\v; Hospodarsky, G.; Parrot, M.; Kurth, W.; Kletzing, C.; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083918 |
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Lightning Contribution to Overall Whistler Mode Wave Intensities in the Plasmasphere Electromagnetic waves generated by lightning propagate into the plasmasphere as dispersed whistlers. They can therefore influence the overall wave intensity in space, which, in turn, is important for dynamics of the Van Allen radiation belts. We analyze spacecraft measurements in low-Earth orbit as well as in high-altitude equatorial region, together with a ground-based estimate of lightning activity. We accumulate wave intensities when the spacecraft are magnetically connected to thunderstorms and compare them with measurements obtained when thunderstorms are absent. We show that strong lightning activity substantially affects the wave intensity in a wide range of L-shells and altitudes. The effect is observed mainly between 500 Hz and 4 kHz, but its frequency range strongly varies with L-shell, extending up to 12 kHz for L lower than 3. The effect is stronger in the afternoon, evening, and night sectors, consistent with more lightning and easier wave propagation through the ionosphere. ahlava, J.; emec, F.; Santolik, O.; a, Kolma\v; Hospodarsky, G.; Parrot, M.; Kurth, W.; Kletzing, C.; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083918 |
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Lightning Contribution to Overall Whistler Mode Wave Intensities in the Plasmasphere Electromagnetic waves generated by lightning propagate into the plasmasphere as dispersed whistlers. They can therefore influence the overall wave intensity in space, which, in turn, is important for dynamics of the Van Allen radiation belts. We analyze spacecraft measurements in low-Earth orbit as well as in high-altitude equatorial region, together with a ground-based estimate of lightning activity. We accumulate wave intensities when the spacecraft are magnetically connected to thunderstorms and compare them with measurements obtained when thunderstorms are absent. We show that strong lightning activity substantially affects the wave intensity in a wide range of L-shells and altitudes. The effect is observed mainly between 500 Hz and 4 kHz, but its frequency range strongly varies with L-shell, extending up to 12 kHz for L lower than 3. The effect is stronger in the afternoon, evening, and night sectors, consistent with more lightning and easier wave propagation through the ionosphere. ahlava, J.; emec, F.; Santolik, O.; a, Kolma\v; Hospodarsky, G.; Parrot, M.; Kurth, W.; Kletzing, C.; Published by: Geophysical Research Letters Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019GL083918 |
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Temperature Dependence of Plasmaspheric Ion Composition We analyze a database of Dynamics Explorer-1 (DE-1) Retarding Ion Mass Spectrometer densities and temperatures to yield the first explicit measure of how cold ion concentration depends on temperature. We find that cold H+ and He+ concentrations have very weak dependence on temperature, but cold O+ ion concentration increases steeply as these ions become warmer. We demonstrate how this result can aid in analyzing composition data from other satellites without spacecraft potential mitigation, by applying the result to an example using data from the Van Allen Probes mission. Measurement of light ion concentrations above 1 electron volt (eV) are a reasonable proxy for the concentrations of colder (eV) ions. Warmer O+ ion concentrations may be extrapolated to colder temperatures using our fit to the statistical distribution versus temperature. Goldstein, J.; Gallagher, D.; Craven, P.; Comfort, R.; Genestreti, K.; Mouikis, C.; Spence, H.; Kurth, W.; Wygant, J.; Skoug, R.; Larsen, B.; Reeves, G.; De Pascuale, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026822 composition; plasmasphere: ion; temperature; Van Allen Probes |
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Temperature Dependence of Plasmaspheric Ion Composition We analyze a database of Dynamics Explorer-1 (DE-1) Retarding Ion Mass Spectrometer densities and temperatures to yield the first explicit measure of how cold ion concentration depends on temperature. We find that cold H+ and He+ concentrations have very weak dependence on temperature, but cold O+ ion concentration increases steeply as these ions become warmer. We demonstrate how this result can aid in analyzing composition data from other satellites without spacecraft potential mitigation, by applying the result to an example using data from the Van Allen Probes mission. Measurement of light ion concentrations above 1 electron volt (eV) are a reasonable proxy for the concentrations of colder (eV) ions. Warmer O+ ion concentrations may be extrapolated to colder temperatures using our fit to the statistical distribution versus temperature. Goldstein, J.; Gallagher, D.; Craven, P.; Comfort, R.; Genestreti, K.; Mouikis, C.; Spence, H.; Kurth, W.; Wygant, J.; Skoug, R.; Larsen, B.; Reeves, G.; De Pascuale, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026822 composition; plasmasphere: ion; temperature; Van Allen Probes |
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Temperature Dependence of Plasmaspheric Ion Composition We analyze a database of Dynamics Explorer-1 (DE-1) Retarding Ion Mass Spectrometer densities and temperatures to yield the first explicit measure of how cold ion concentration depends on temperature. We find that cold H+ and He+ concentrations have very weak dependence on temperature, but cold O+ ion concentration increases steeply as these ions become warmer. We demonstrate how this result can aid in analyzing composition data from other satellites without spacecraft potential mitigation, by applying the result to an example using data from the Van Allen Probes mission. Measurement of light ion concentrations above 1 electron volt (eV) are a reasonable proxy for the concentrations of colder (eV) ions. Warmer O+ ion concentrations may be extrapolated to colder temperatures using our fit to the statistical distribution versus temperature. Goldstein, J.; Gallagher, D.; Craven, P.; Comfort, R.; Genestreti, K.; Mouikis, C.; Spence, H.; Kurth, W.; Wygant, J.; Skoug, R.; Larsen, B.; Reeves, G.; De Pascuale, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026822 composition; plasmasphere: ion; temperature; Van Allen Probes |
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Temperature Dependence of Plasmaspheric Ion Composition We analyze a database of Dynamics Explorer-1 (DE-1) Retarding Ion Mass Spectrometer densities and temperatures to yield the first explicit measure of how cold ion concentration depends on temperature. We find that cold H+ and He+ concentrations have very weak dependence on temperature, but cold O+ ion concentration increases steeply as these ions become warmer. We demonstrate how this result can aid in analyzing composition data from other satellites without spacecraft potential mitigation, by applying the result to an example using data from the Van Allen Probes mission. Measurement of light ion concentrations above 1 electron volt (eV) are a reasonable proxy for the concentrations of colder (eV) ions. Warmer O+ ion concentrations may be extrapolated to colder temperatures using our fit to the statistical distribution versus temperature. Goldstein, J.; Gallagher, D.; Craven, P.; Comfort, R.; Genestreti, K.; Mouikis, C.; Spence, H.; Kurth, W.; Wygant, J.; Skoug, R.; Larsen, B.; Reeves, G.; De Pascuale, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026822 composition; plasmasphere: ion; temperature; Van Allen Probes |
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Using Van Allen Probe Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) wave observations from September 2012 to May 2018, we statistically investigate the distributions of power-weighted wave normal angle (WNA) of fast magnetosonic (MS) waves from L = 2\textendash6 within \textpm15\textdegree geomagnetic latitudes. The spatial distributions show that the MS WNAs are mainly confined within 87\textendash89\textdegree near the geomagnetic equator and decrease with increasing magnetic latitude. Further quantitative investigation demonstrates that the WNAs normally distribute as a mixture of two Gaussian distributions ranging from 85\textdegree to 88\textdegree, and the tangent of it can decrease as a Kappa distribution function when the waves propagate to higher latitudes. Our study completes the survey of spatial distributions of MS WNAs and provides quantitative dependence of the WNA distribution on the magnetic latitude in the inner magnetosphere, which can be readily useful in future global simulations of radiation belt particle dynamics. Zou, Zhengyang; Zuo, Pingbing; Ni, Binbin; Wei, Fengsi; Zhao, Zhengyu; Cao, Xing; Fu, Song; Gu, Xudong; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026556 Empirical Model; Fast Magnetosonic Waves; latitudinal dependence; power-weighted wave normal angles; spatial distributions; Van Allen Probes |
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Using Van Allen Probe Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) wave observations from September 2012 to May 2018, we statistically investigate the distributions of power-weighted wave normal angle (WNA) of fast magnetosonic (MS) waves from L = 2\textendash6 within \textpm15\textdegree geomagnetic latitudes. The spatial distributions show that the MS WNAs are mainly confined within 87\textendash89\textdegree near the geomagnetic equator and decrease with increasing magnetic latitude. Further quantitative investigation demonstrates that the WNAs normally distribute as a mixture of two Gaussian distributions ranging from 85\textdegree to 88\textdegree, and the tangent of it can decrease as a Kappa distribution function when the waves propagate to higher latitudes. Our study completes the survey of spatial distributions of MS WNAs and provides quantitative dependence of the WNA distribution on the magnetic latitude in the inner magnetosphere, which can be readily useful in future global simulations of radiation belt particle dynamics. Zou, Zhengyang; Zuo, Pingbing; Ni, Binbin; Wei, Fengsi; Zhao, Zhengyu; Cao, Xing; Fu, Song; Gu, Xudong; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026556 Empirical Model; Fast Magnetosonic Waves; latitudinal dependence; power-weighted wave normal angles; spatial distributions; Van Allen Probes |
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Using Van Allen Probe Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) wave observations from September 2012 to May 2018, we statistically investigate the distributions of power-weighted wave normal angle (WNA) of fast magnetosonic (MS) waves from L = 2\textendash6 within \textpm15\textdegree geomagnetic latitudes. The spatial distributions show that the MS WNAs are mainly confined within 87\textendash89\textdegree near the geomagnetic equator and decrease with increasing magnetic latitude. Further quantitative investigation demonstrates that the WNAs normally distribute as a mixture of two Gaussian distributions ranging from 85\textdegree to 88\textdegree, and the tangent of it can decrease as a Kappa distribution function when the waves propagate to higher latitudes. Our study completes the survey of spatial distributions of MS WNAs and provides quantitative dependence of the WNA distribution on the magnetic latitude in the inner magnetosphere, which can be readily useful in future global simulations of radiation belt particle dynamics. Zou, Zhengyang; Zuo, Pingbing; Ni, Binbin; Wei, Fengsi; Zhao, Zhengyu; Cao, Xing; Fu, Song; Gu, Xudong; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019 YEAR: 2019 DOI: 10.1029/2019JA026556 Empirical Model; Fast Magnetosonic Waves; latitudinal dependence; power-weighted wave normal angles; spatial distributions; Van Allen Probes |