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Found 2758 entries in the Bibliography.
Showing entries from 1351 through 1400
| 2017 |
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An interesting form of \textquotedblleftzipper-like\textquotedblright magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Magnetospheric Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisatellite observations shows that zipper-like magnetosonic waves mainly occur on the dawnside to noonside, in a frequency range between 10 fcp and fLHR. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood. Li, J.; Bortnik, J.; Li, W.; Ma, Q.; Thorne, R.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Wygant, J.; Breneman, A.; Thaller, S.; Funsten, H.; Mitchell, D.; Manweiler, J.; Torbert, R.; Le Contel, O.; Ergun, R.; Lindqvist, P.-A.; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023536 magnetosonic wave; Radiation belt; rising-tone; Van Allen Probes; zipper-like |
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An interesting form of \textquotedblleftzipper-like\textquotedblright magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Magnetospheric Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisatellite observations shows that zipper-like magnetosonic waves mainly occur on the dawnside to noonside, in a frequency range between 10 fcp and fLHR. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood. Li, J.; Bortnik, J.; Li, W.; Ma, Q.; Thorne, R.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Wygant, J.; Breneman, A.; Thaller, S.; Funsten, H.; Mitchell, D.; Manweiler, J.; Torbert, R.; Le Contel, O.; Ergun, R.; Lindqvist, P.-A.; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023536 magnetosonic wave; Radiation belt; rising-tone; Van Allen Probes; zipper-like |
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An interesting form of \textquotedblleftzipper-like\textquotedblright magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Magnetospheric Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisatellite observations shows that zipper-like magnetosonic waves mainly occur on the dawnside to noonside, in a frequency range between 10 fcp and fLHR. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood. Li, J.; Bortnik, J.; Li, W.; Ma, Q.; Thorne, R.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Wygant, J.; Breneman, A.; Thaller, S.; Funsten, H.; Mitchell, D.; Manweiler, J.; Torbert, R.; Le Contel, O.; Ergun, R.; Lindqvist, P.-A.; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023536 magnetosonic wave; Radiation belt; rising-tone; Van Allen Probes; zipper-like |
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An interesting form of \textquotedblleftzipper-like\textquotedblright magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Magnetospheric Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisatellite observations shows that zipper-like magnetosonic waves mainly occur on the dawnside to noonside, in a frequency range between 10 fcp and fLHR. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood. Li, J.; Bortnik, J.; Li, W.; Ma, Q.; Thorne, R.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Wygant, J.; Breneman, A.; Thaller, S.; Funsten, H.; Mitchell, D.; Manweiler, J.; Torbert, R.; Le Contel, O.; Ergun, R.; Lindqvist, P.-A.; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023536 magnetosonic wave; Radiation belt; rising-tone; Van Allen Probes; zipper-like |
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Acceleration at Dipolarization Fronts in the Inner Magnetosphere During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds keV. Plasma pressure is the source of global storm-time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent analysis showed that the buildup of hot ion population in the inner magnetosphere largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field, similar to dipolarization fronts in the magnetotail. Because of significant differences between the ambient magnetic field and the dipolarization front properties in the magnetotail and the inner magnetosphere, the physical mechanisms of ion acceleration at dipolarization fronts in these two regions may also be different. In this paper we discuss a new acceleration mechanism enabled by stable trapping of ions at the azimuthally localized dipolarization fronts. It is shown that trapping can provide a robust mechanism of ion energization in the inner magnetosphere even in the absence of large electric fields. Ukhorskiy, A; Sitnov, M.; Merkin, V.; Gkioulidou, M.; Mitchell, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016ja023304 |
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Acceleration at Dipolarization Fronts in the Inner Magnetosphere During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds keV. Plasma pressure is the source of global storm-time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent analysis showed that the buildup of hot ion population in the inner magnetosphere largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field, similar to dipolarization fronts in the magnetotail. Because of significant differences between the ambient magnetic field and the dipolarization front properties in the magnetotail and the inner magnetosphere, the physical mechanisms of ion acceleration at dipolarization fronts in these two regions may also be different. In this paper we discuss a new acceleration mechanism enabled by stable trapping of ions at the azimuthally localized dipolarization fronts. It is shown that trapping can provide a robust mechanism of ion energization in the inner magnetosphere even in the absence of large electric fields. Ukhorskiy, A; Sitnov, M.; Merkin, V.; Gkioulidou, M.; Mitchell, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016ja023304 |
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Acceleration at Dipolarization Fronts in the Inner Magnetosphere During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds keV. Plasma pressure is the source of global storm-time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent analysis showed that the buildup of hot ion population in the inner magnetosphere largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field, similar to dipolarization fronts in the magnetotail. Because of significant differences between the ambient magnetic field and the dipolarization front properties in the magnetotail and the inner magnetosphere, the physical mechanisms of ion acceleration at dipolarization fronts in these two regions may also be different. In this paper we discuss a new acceleration mechanism enabled by stable trapping of ions at the azimuthally localized dipolarization fronts. It is shown that trapping can provide a robust mechanism of ion energization in the inner magnetosphere even in the absence of large electric fields. Ukhorskiy, A; Sitnov, M.; Merkin, V.; Gkioulidou, M.; Mitchell, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016ja023304 |
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Climatology of high-β plasma measurements in Earth\textquoterights inner magnetosphere Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high-resolution measurements of Earth\textquoterights ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high-beta (β) plasma events (defined here as β > 1) as measured by the RBSPICE instrument in the \~45 keV to \~600 keV proton energy range in the inner magnetosphere (L < 5.8) has been constructed. In this paper we report this climatology of such high-β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high-β events in the RBSPICE energy range are associated with postdusk/premidnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a β less than 2, there are a number of observations reaching β greater than 4. Other observations of particular note are high-β events during relatively minor geomagnetic storms and examples of very long duration high-β plasmas. We show that high-β plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an underappreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed. Cohen, Ross; Gerrard, Andrew; Lanzerotti, Louis; Soto-Chavez, A.; Kim, Hyomin; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA022513 climatology; high-beta plasma; inner magnetosphere; RBSPICE; Van Allen Probes |
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Climatology of high-β plasma measurements in Earth\textquoterights inner magnetosphere Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high-resolution measurements of Earth\textquoterights ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high-beta (β) plasma events (defined here as β > 1) as measured by the RBSPICE instrument in the \~45 keV to \~600 keV proton energy range in the inner magnetosphere (L < 5.8) has been constructed. In this paper we report this climatology of such high-β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high-β events in the RBSPICE energy range are associated with postdusk/premidnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a β less than 2, there are a number of observations reaching β greater than 4. Other observations of particular note are high-β events during relatively minor geomagnetic storms and examples of very long duration high-β plasmas. We show that high-β plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an underappreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed. Cohen, Ross; Gerrard, Andrew; Lanzerotti, Louis; Soto-Chavez, A.; Kim, Hyomin; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA022513 climatology; high-beta plasma; inner magnetosphere; RBSPICE; Van Allen Probes |
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Climatology of high-β plasma measurements in Earth\textquoterights inner magnetosphere Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high-resolution measurements of Earth\textquoterights ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high-beta (β) plasma events (defined here as β > 1) as measured by the RBSPICE instrument in the \~45 keV to \~600 keV proton energy range in the inner magnetosphere (L < 5.8) has been constructed. In this paper we report this climatology of such high-β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high-β events in the RBSPICE energy range are associated with postdusk/premidnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a β less than 2, there are a number of observations reaching β greater than 4. Other observations of particular note are high-β events during relatively minor geomagnetic storms and examples of very long duration high-β plasmas. We show that high-β plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an underappreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed. Cohen, Ross; Gerrard, Andrew; Lanzerotti, Louis; Soto-Chavez, A.; Kim, Hyomin; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA022513 climatology; high-beta plasma; inner magnetosphere; RBSPICE; Van Allen Probes |
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We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick\textquoterights 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 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes 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. The cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure. Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; Funsten, H.; Kurth, W.; LLera, K.; McComas, D.; Perez, J.; Reeves, G.; Spence, H.; Thaller, S.; Valek, P.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023173 Heliophysics System Observatory; Modeling; multimission; THEMIS; TWINS; Van Allen Probes |
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We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick\textquoterights 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 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes 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. The cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure. Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; Funsten, H.; Kurth, W.; LLera, K.; McComas, D.; Perez, J.; Reeves, G.; Spence, H.; Thaller, S.; Valek, P.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023173 Heliophysics System Observatory; Modeling; multimission; THEMIS; TWINS; Van Allen Probes |
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We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick\textquoterights 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 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes 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. The cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure. Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; Funsten, H.; Kurth, W.; LLera, K.; McComas, D.; Perez, J.; Reeves, G.; Spence, H.; Thaller, S.; Valek, P.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/2016JA023173 Heliophysics System Observatory; Modeling; multimission; THEMIS; TWINS; Van Allen Probes |
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We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick\textquoterights 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 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes 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. The cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure. Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; Funsten, H.; Kurth, W.; LLera, K.; McComas, D.; Perez, J.; Reeves, G.; Spence, H.; Thaller, S.; Valek, P.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/jgra.v122.110.1002/2016JA023173 Heliophysics System Observatory; Modeling; multimission; THEMIS; TWINS; Van Allen Probes |
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We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick\textquoterights 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 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes 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. The cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure. Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; Funsten, H.; Kurth, W.; LLera, K.; McComas, D.; Perez, J.; Reeves, G.; Spence, H.; Thaller, S.; Valek, P.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/jgra.v122.110.1002/2016JA023173 Heliophysics System Observatory; Modeling; multimission; THEMIS; TWINS; Van Allen Probes |
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We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick\textquoterights 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 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes 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. The cross-scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure. Goldstein, J.; Angelopoulos, V.; De Pascuale, S.; Funsten, H.; Kurth, W.; LLera, K.; McComas, D.; Perez, J.; Reeves, G.; Spence, H.; Thaller, S.; Valek, P.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/jgra.v122.110.1002/2016JA023173 Heliophysics System Observatory; Modeling; multimission; THEMIS; TWINS; Van Allen Probes |
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Radial diffusion is one of the dominant physical mechanisms that drives acceleration and loss of the radiation belt electrons, which makes it very important for nowcasting and forecasting space weather models. We investigate the sensitivity of the two parameterizations of the radial diffusion of Brautigam and Albert (2000) and Ozeke et al. (2014) on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB). Following Brautigam and Albert (2000) and Ozeke et al. (2014), we first perform 1-D radial diffusion simulations. Comparison of the simulation results with observations shows that the difference between simulations with either radial diffusion parameterization is small. To take into account effects of local acceleration and loss, we perform 3-D simulations, including pitch angle, energy, and mixed diffusion. We found that the results of 3-D simulations are even less sensitive to the choice of parameterization of radial diffusion rates than the results of 1-D simulations at various energies (from 0.59 to 1.80 MeV). This result demonstrates that the inclusion of local acceleration and pitch angle diffusion can provide a negative feedback effect, such that the result is largely indistinguishable simulations conducted with different radial diffusion parameterizations. We also perform a number of sensitivity tests by multiplying radial diffusion rates by constant factors and show that such an approach leads to unrealistic predictions of radiation belt dynamics. Drozdov, A; Shprits, Y; Aseev, N.; Kellerman, A.; Reeves, G.; Published by: Space Weather Published on: 01/2017 YEAR: 2017 DOI: 10.1002/swe.v15.110.1002/2016SW001426 radial diffusion; Radiation belts; Van Allen Probes; VERB code |
| 2016 |
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Climatology of high β plasma measurements in Earth\textquoterights inner magnetosphere Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high resolution measurements of Earth\textquoterights ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high beta (β) plasma events (defined here as β>1) as measured by the RBSPICE instrument in the \~45-keV to \~600-keV proton energy range in the inner magnetosphere (L<5.8) has been constructed. In this paper we report this climatology of such high β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high β events in the RBSPICE energy range are associated with post-dusk/pre-midnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a β less than 2, there are a number of observations reaching β greater than 4. Other observations of particular note are high β events during relatively minor geomagnetic storms and examples of very long duration high β plasmas. We show that high β plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an under-appreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed. Cohen, Ross; Gerrard, Andrew; Lanzerotti, Louis; Soto-Chavez, A.; Kim, Hyomin; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA022513 climatology; high beta plasma; inner magnetosphere; RBSPICE; Van Allen Probes |
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Climatology of high β plasma measurements in Earth\textquoterights inner magnetosphere Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high resolution measurements of Earth\textquoterights ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high beta (β) plasma events (defined here as β>1) as measured by the RBSPICE instrument in the \~45-keV to \~600-keV proton energy range in the inner magnetosphere (L<5.8) has been constructed. In this paper we report this climatology of such high β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high β events in the RBSPICE energy range are associated with post-dusk/pre-midnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a β less than 2, there are a number of observations reaching β greater than 4. Other observations of particular note are high β events during relatively minor geomagnetic storms and examples of very long duration high β plasmas. We show that high β plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an under-appreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed. Cohen, Ross; Gerrard, Andrew; Lanzerotti, Louis; Soto-Chavez, A.; Kim, Hyomin; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA022513 climatology; high beta plasma; inner magnetosphere; RBSPICE; Van Allen Probes |
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Climatology of high β plasma measurements in Earth\textquoterights inner magnetosphere Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high resolution measurements of Earth\textquoterights ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high beta (β) plasma events (defined here as β>1) as measured by the RBSPICE instrument in the \~45-keV to \~600-keV proton energy range in the inner magnetosphere (L<5.8) has been constructed. In this paper we report this climatology of such high β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high β events in the RBSPICE energy range are associated with post-dusk/pre-midnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a β less than 2, there are a number of observations reaching β greater than 4. Other observations of particular note are high β events during relatively minor geomagnetic storms and examples of very long duration high β plasmas. We show that high β plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an under-appreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed. Cohen, Ross; Gerrard, Andrew; Lanzerotti, Louis; Soto-Chavez, A.; Kim, Hyomin; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA022513 climatology; high beta plasma; inner magnetosphere; RBSPICE; Van Allen Probes |
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Electron holes in the outer radiation belt: Characteristics and their role in electron energization Van Allen Probes have detected electron holes (EHs) around injection fronts in the outer radiation belt. Presumably generated near equator, EHs propagate to higher latitudes potentially resulting in energization of electrons trapped within EHs. This process has been recently shown to provide electrons with energies up to several tens of keV and requires EH propagation up to rather high latitudes. We have analyzed more than 100 EHs observed around a particular injection to determine their kinetic structure and potential energy sources supporting the energization of trapped electrons. EHs propagate with velocities from 1000 to 20,000 km/s (a few times larger than the thermal velocity of the coldest background electron population). The parallel scale of observed EHs is from 0.3 to 3 km that is of the order of hundred Debye lengths. The perpendicular to parallel scale ratio is larger than one in a qualitative agreement with the theoretical scaling relation. The amplitudes of EH electrostatic potentials are generally below 100 V. We determine the properties of the electron population trapped within EHs by making use of the Bernstein-Green-Kruskal analysis and via analysis of EH magnetic field signatures. The density of the trapped electron population is on average 20\% of the background electron density. The perpendicular temperature of the trapped population is on average 300 eV and is larger for faster EHs. We show that energy losses of untrapped electrons scattered by EHs in the inhomogeneous background magnetic field may balance the energization of trapped electrons. Vasko, I; Agapitov, O.; Mozer, F.; Artemyev, A.; Drake, J.; Kuzichev, I.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023083 Electron acceleration; electron holes; injection; Radiation belt; solitary waves; Van Allen Probes |
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Electron holes in the outer radiation belt: Characteristics and their role in electron energization Van Allen Probes have detected electron holes (EHs) around injection fronts in the outer radiation belt. Presumably generated near equator, EHs propagate to higher latitudes potentially resulting in energization of electrons trapped within EHs. This process has been recently shown to provide electrons with energies up to several tens of keV and requires EH propagation up to rather high latitudes. We have analyzed more than 100 EHs observed around a particular injection to determine their kinetic structure and potential energy sources supporting the energization of trapped electrons. EHs propagate with velocities from 1000 to 20,000 km/s (a few times larger than the thermal velocity of the coldest background electron population). The parallel scale of observed EHs is from 0.3 to 3 km that is of the order of hundred Debye lengths. The perpendicular to parallel scale ratio is larger than one in a qualitative agreement with the theoretical scaling relation. The amplitudes of EH electrostatic potentials are generally below 100 V. We determine the properties of the electron population trapped within EHs by making use of the Bernstein-Green-Kruskal analysis and via analysis of EH magnetic field signatures. The density of the trapped electron population is on average 20\% of the background electron density. The perpendicular temperature of the trapped population is on average 300 eV and is larger for faster EHs. We show that energy losses of untrapped electrons scattered by EHs in the inhomogeneous background magnetic field may balance the energization of trapped electrons. Vasko, I; Agapitov, O.; Mozer, F.; Artemyev, A.; Drake, J.; Kuzichev, I.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023083 Electron acceleration; electron holes; injection; Radiation belt; solitary waves; Van Allen Probes |
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Electron holes in the outer radiation belt: Characteristics and their role in electron energization Van Allen Probes have detected electron holes (EHs) around injection fronts in the outer radiation belt. Presumably generated near equator, EHs propagate to higher latitudes potentially resulting in energization of electrons trapped within EHs. This process has been recently shown to provide electrons with energies up to several tens of keV and requires EH propagation up to rather high latitudes. We have analyzed more than 100 EHs observed around a particular injection to determine their kinetic structure and potential energy sources supporting the energization of trapped electrons. EHs propagate with velocities from 1000 to 20,000 km/s (a few times larger than the thermal velocity of the coldest background electron population). The parallel scale of observed EHs is from 0.3 to 3 km that is of the order of hundred Debye lengths. The perpendicular to parallel scale ratio is larger than one in a qualitative agreement with the theoretical scaling relation. The amplitudes of EH electrostatic potentials are generally below 100 V. We determine the properties of the electron population trapped within EHs by making use of the Bernstein-Green-Kruskal analysis and via analysis of EH magnetic field signatures. The density of the trapped electron population is on average 20\% of the background electron density. The perpendicular temperature of the trapped population is on average 300 eV and is larger for faster EHs. We show that energy losses of untrapped electrons scattered by EHs in the inhomogeneous background magnetic field may balance the energization of trapped electrons. Vasko, I; Agapitov, O.; Mozer, F.; Artemyev, A.; Drake, J.; Kuzichev, I.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023083 Electron acceleration; electron holes; injection; Radiation belt; solitary waves; Van Allen Probes |
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Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts Auroral kilometric radiation (AKR) is a strong terrestrial radio emission and dominates at higher latitudes because of reflection in vicinities of the source cavity and plasmapause. Recently, Van Allen Probes have observed occurrences of AKR emission in the equatorial region of Earth\textquoterights radiation belts but its origin still remains an open question. Equatorial AKR can produce efficient acceleration of radiation belt electrons and is a risk to space weather. Here we report high-resolution observations during two small storm periods 4\textendash6 April and 18\textendash20 May 2013 and show, using a 3-D ray tracing simulation, that AKR can propagate downward all the way into the equatorial plane in the radiation belts under appropriate conditions. The simulated results can successfully explain the observed AKR\textquoterights spatial distribution and frequency range, and the current results have a wide application to all other magnetized astrophysical objects in the universe. Xiao, Fuliang; Zhou, Qinghua; Su, Zhenpeng; He, Zhaoguo; Yang, Chang; Liu, Si; He, Yihua; Gao, Zhonglei; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071728 AKR emissions; Geomagnetic storms; Radiation belts; ray tracing simulations; satellite data; Van Allen Probes |
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Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts Auroral kilometric radiation (AKR) is a strong terrestrial radio emission and dominates at higher latitudes because of reflection in vicinities of the source cavity and plasmapause. Recently, Van Allen Probes have observed occurrences of AKR emission in the equatorial region of Earth\textquoterights radiation belts but its origin still remains an open question. Equatorial AKR can produce efficient acceleration of radiation belt electrons and is a risk to space weather. Here we report high-resolution observations during two small storm periods 4\textendash6 April and 18\textendash20 May 2013 and show, using a 3-D ray tracing simulation, that AKR can propagate downward all the way into the equatorial plane in the radiation belts under appropriate conditions. The simulated results can successfully explain the observed AKR\textquoterights spatial distribution and frequency range, and the current results have a wide application to all other magnetized astrophysical objects in the universe. Xiao, Fuliang; Zhou, Qinghua; Su, Zhenpeng; He, Zhaoguo; Yang, Chang; Liu, Si; He, Yihua; Gao, Zhonglei; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071728 AKR emissions; Geomagnetic storms; Radiation belts; ray tracing simulations; satellite data; Van Allen Probes |
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Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts Auroral kilometric radiation (AKR) is a strong terrestrial radio emission and dominates at higher latitudes because of reflection in vicinities of the source cavity and plasmapause. Recently, Van Allen Probes have observed occurrences of AKR emission in the equatorial region of Earth\textquoterights radiation belts but its origin still remains an open question. Equatorial AKR can produce efficient acceleration of radiation belt electrons and is a risk to space weather. Here we report high-resolution observations during two small storm periods 4\textendash6 April and 18\textendash20 May 2013 and show, using a 3-D ray tracing simulation, that AKR can propagate downward all the way into the equatorial plane in the radiation belts under appropriate conditions. The simulated results can successfully explain the observed AKR\textquoterights spatial distribution and frequency range, and the current results have a wide application to all other magnetized astrophysical objects in the universe. Xiao, Fuliang; Zhou, Qinghua; Su, Zhenpeng; He, Zhaoguo; Yang, Chang; Liu, Si; He, Yihua; Gao, Zhonglei; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071728 AKR emissions; Geomagnetic storms; Radiation belts; ray tracing simulations; satellite data; Van Allen Probes |
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We present here the first in situ statistical survey of structured Pc1 pearl pulsations compared with unstructured electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes spacecraft. This data set was compiled from observations spanning 8 September 2012 through 31 August 2015 and comprises over 1630 h of total EMIC wave activity, of which 291 h exhibited pearl structure. Additionally, we have identified 29 wave events demonstrating periodically oscillating wave packets, mostly about the magnetic equator, indicated by the reversal of Poynting flux along the background magnetic field. We have found several stark differences between Pc1 pearl pulsations and unstructured EMIC waves. While unstructured EMIC waves demonstrate the predicted behavior of a higher occurrence across the dayside with enhanced wave power at dusk, pearl pulsations occur uniformly across magnetic local time, with a small enhancement in the late morning sector. Pearl pulsations were more often observed during magnetospherically quiet periods, particularly in the late recovery period of geomagnetic storms. The mean excitation frequency of pearl pulsations was observed to be independent of the local ion cyclotron frequency, and individual wave investigations indicate that the modulation period also remained constant for the duration of the event over a finite range in L. We examine three possible generation mechanisms\textemdashthe bouncing wave packet model, modulation by ultralow-frequency Pc4 and Pc5 waves, and the formation of an ion cyclotron resonator\textemdashbut are unable to definitively confirm the validity of any one model. Paulson, K.; Smith, C.; Lessard, M.; Torbert, R.; Kletzing, C.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023160 |
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We present here the first in situ statistical survey of structured Pc1 pearl pulsations compared with unstructured electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes spacecraft. This data set was compiled from observations spanning 8 September 2012 through 31 August 2015 and comprises over 1630 h of total EMIC wave activity, of which 291 h exhibited pearl structure. Additionally, we have identified 29 wave events demonstrating periodically oscillating wave packets, mostly about the magnetic equator, indicated by the reversal of Poynting flux along the background magnetic field. We have found several stark differences between Pc1 pearl pulsations and unstructured EMIC waves. While unstructured EMIC waves demonstrate the predicted behavior of a higher occurrence across the dayside with enhanced wave power at dusk, pearl pulsations occur uniformly across magnetic local time, with a small enhancement in the late morning sector. Pearl pulsations were more often observed during magnetospherically quiet periods, particularly in the late recovery period of geomagnetic storms. The mean excitation frequency of pearl pulsations was observed to be independent of the local ion cyclotron frequency, and individual wave investigations indicate that the modulation period also remained constant for the duration of the event over a finite range in L. We examine three possible generation mechanisms\textemdashthe bouncing wave packet model, modulation by ultralow-frequency Pc4 and Pc5 waves, and the formation of an ion cyclotron resonator\textemdashbut are unable to definitively confirm the validity of any one model. Paulson, K.; Smith, C.; Lessard, M.; Torbert, R.; Kletzing, C.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023160 |
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Using observations from NASA\textquoterights Van Allen Probes, we study the role of sudden particle enhancements at low L-shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than one day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not the dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can exceed three orders of magnitude in the slot region and continues into the inner radiation belt, which is evidence that these events are an important - and potentially dominant - source of inner belt electrons. Electron fluxes from September 2012 through February 2016 reveal that SPELLS occur frequently (~2.5/month at 200 keV), but the number of observed events decreases exponentially with increasing electron energy for >=100 keV. After SPELLS events, the slot region reforms due to slow energy-dependent decay over several day timescales, consistent with losses due to interactions with plasmaspheric hiss. Combined, these results indicate that the peaked phase space density distributions in the inner electron radiation belt result from an \textquotedbllefton/off\textquotedblright, geomagnetic-activity-dependent source from higher radial distances. Turner, D.; O\textquoterightBrien, T.; Fennell, J.; Claudepierre, S.; Blake, J.; Jaynes, A.; Baker, D.; Kanekal, S.; Gkioulidou, M.; Henderson, M.; Reeves, G.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023600 2720 Energetic Particles; trapped; 2730 Magnetosphere: inner; 2774 Radiation belts; 7807 Charged particle motion and acceleration; 7984 Space radiation environment; energetic particle injections; inner magnetosphere; Radiation belts; relativistic electrons; Van Allen Probes |
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Using observations from NASA\textquoterights Van Allen Probes, we study the role of sudden particle enhancements at low L-shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than one day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not the dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can exceed three orders of magnitude in the slot region and continues into the inner radiation belt, which is evidence that these events are an important - and potentially dominant - source of inner belt electrons. Electron fluxes from September 2012 through February 2016 reveal that SPELLS occur frequently (~2.5/month at 200 keV), but the number of observed events decreases exponentially with increasing electron energy for >=100 keV. After SPELLS events, the slot region reforms due to slow energy-dependent decay over several day timescales, consistent with losses due to interactions with plasmaspheric hiss. Combined, these results indicate that the peaked phase space density distributions in the inner electron radiation belt result from an \textquotedbllefton/off\textquotedblright, geomagnetic-activity-dependent source from higher radial distances. Turner, D.; O\textquoterightBrien, T.; Fennell, J.; Claudepierre, S.; Blake, J.; Jaynes, A.; Baker, D.; Kanekal, S.; Gkioulidou, M.; Henderson, M.; Reeves, G.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023600 2720 Energetic Particles; trapped; 2730 Magnetosphere: inner; 2774 Radiation belts; 7807 Charged particle motion and acceleration; 7984 Space radiation environment; energetic particle injections; inner magnetosphere; Radiation belts; relativistic electrons; Van Allen Probes |
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Using observations from NASA\textquoterights Van Allen Probes, we study the role of sudden particle enhancements at low L-shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than one day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not the dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can exceed three orders of magnitude in the slot region and continues into the inner radiation belt, which is evidence that these events are an important - and potentially dominant - source of inner belt electrons. Electron fluxes from September 2012 through February 2016 reveal that SPELLS occur frequently (~2.5/month at 200 keV), but the number of observed events decreases exponentially with increasing electron energy for >=100 keV. After SPELLS events, the slot region reforms due to slow energy-dependent decay over several day timescales, consistent with losses due to interactions with plasmaspheric hiss. Combined, these results indicate that the peaked phase space density distributions in the inner electron radiation belt result from an \textquotedbllefton/off\textquotedblright, geomagnetic-activity-dependent source from higher radial distances. Turner, D.; O\textquoterightBrien, T.; Fennell, J.; Claudepierre, S.; Blake, J.; Jaynes, A.; Baker, D.; Kanekal, S.; Gkioulidou, M.; Henderson, M.; Reeves, G.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023600 2720 Energetic Particles; trapped; 2730 Magnetosphere: inner; 2774 Radiation belts; 7807 Charged particle motion and acceleration; 7984 Space radiation environment; energetic particle injections; inner magnetosphere; Radiation belts; relativistic electrons; Van Allen Probes |
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We conduct a statistical study on the sudden response of outer radiation belt electrons due to interplanetary (IP) shocks during the Van Allen Probes era, i.e., 2012 to 2015. Data from the Relativistic Electron-Proton Telescope instrument on board Van Allen Probes are used to investigate the highly relativistic electron response (E > 1.8 MeV) within the first few minutes after shock impact. We investigate the relationship of IP shock parameters, such as Mach number, with the highly relativistic electron response, including spectral properties and radial location of the shock-induced injection. We find that the driving solar wind structure of the shock does not affect occurrence for enhancement events, 25\% of IP shocks are associated with prompt energization, and 14\% are associated with MeV electron depletion. Parameters that represent IP shock strength are found to correlate best with highest levels of energization, suggesting that shock strength may play a key role in the severity of the enhancements. However, not every shock results in an enhancement, indicating that magnetospheric preconditioning may be required. Schiller, Q.; Kanekal, S.; Jian, L.; Li, X.; Jones, A.; Baker, D.; Jaynes, A.; Spence, H.; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071628 |
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Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single-peak Gaussian function. Incorporating these realistic EMIC wave frequency spectra into radiation belt models is expected to improve the quantification of EMIC wave scattering effects in ultrarelativistic electron dynamics. Zhang, X.-J.; Li, W.; Thorne, R.; Angelopoulos, V.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071158 EMIC waves; magnetic storm; outer radiation belt; relativistic electron loss; Van Allen Probes; Wave-particle interaction |
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Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single-peak Gaussian function. Incorporating these realistic EMIC wave frequency spectra into radiation belt models is expected to improve the quantification of EMIC wave scattering effects in ultrarelativistic electron dynamics. Zhang, X.-J.; Li, W.; Thorne, R.; Angelopoulos, V.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071158 EMIC waves; magnetic storm; outer radiation belt; relativistic electron loss; Van Allen Probes; Wave-particle interaction |
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Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single-peak Gaussian function. Incorporating these realistic EMIC wave frequency spectra into radiation belt models is expected to improve the quantification of EMIC wave scattering effects in ultrarelativistic electron dynamics. Zhang, X.-J.; Li, W.; Thorne, R.; Angelopoulos, V.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071158 EMIC waves; magnetic storm; outer radiation belt; relativistic electron loss; Van Allen Probes; Wave-particle interaction |
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Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single-peak Gaussian function. Incorporating these realistic EMIC wave frequency spectra into radiation belt models is expected to improve the quantification of EMIC wave scattering effects in ultrarelativistic electron dynamics. Zhang, X.-J.; Li, W.; Thorne, R.; Angelopoulos, V.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071158 EMIC waves; magnetic storm; outer radiation belt; relativistic electron loss; Van Allen Probes; Wave-particle interaction |
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Transitional behavior of different energy protons based on Van Allen Probes observations Understanding the dynamical behavior of ~1 eV to 50 keV ions and identifying the energies at which the morphologies transit are important in that they involve the relative intensities and distributions of the large-scale electric and magnetic fields, the outflow and recombination rates. However, there have been only few direct observational investigations of the transition in drift behaviors of different energy ions before the Van Allen Probes era. Here, we statistically analyze ~1 eV to 50 keV Hydrogen (H+) differential flux distributions near geomagnetic equator by using Van Allen Probes observations to investigate the H+ dynamics under the regulation of large-scale electric and magnetic fields. Our survey clearly indicates three types of H+ behaviors within different energy ranges, which is consistent with previous theory predictions. Using simple electric and magnetic field models in UBK coordinates, we have further constrained the source regions of different energy ions and their drift directions. Yue, Chao; Bortnik, Jacob; Chen, Lunjin; Ma, Qianli; Thorne, Richard; Reeves, Geoffrey; Spence, Harlan; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071324 |
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Transitional behavior of different energy protons based on Van Allen Probes observations Understanding the dynamical behavior of ~1 eV to 50 keV ions and identifying the energies at which the morphologies transit are important in that they involve the relative intensities and distributions of the large-scale electric and magnetic fields, the outflow and recombination rates. However, there have been only few direct observational investigations of the transition in drift behaviors of different energy ions before the Van Allen Probes era. Here, we statistically analyze ~1 eV to 50 keV Hydrogen (H+) differential flux distributions near geomagnetic equator by using Van Allen Probes observations to investigate the H+ dynamics under the regulation of large-scale electric and magnetic fields. Our survey clearly indicates three types of H+ behaviors within different energy ranges, which is consistent with previous theory predictions. Using simple electric and magnetic field models in UBK coordinates, we have further constrained the source regions of different energy ions and their drift directions. Yue, Chao; Bortnik, Jacob; Chen, Lunjin; Ma, Qianli; Thorne, Richard; Reeves, Geoffrey; Spence, Harlan; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071324 |
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The electric drift E \texttimes B/B2 plays a fundamental role for the description of plasma flow and particle acceleration. Yet it is not well-known in the inner belt and slot region because of a lack of reliable in situ measurements. In this article, we present an analysis of the electric drifts measured below L ~ 3 by both Van Allen Probes A and B from September 2012 to December 2014. The objective is to determine the typical components of the equatorial electric drift in both radial and azimuthal directions. The dependences of the components on radial distance, magnetic local time, and geographic longitude are examined. The results from Van Allen Probe A agree with Van Allen Probe B. They show, among other things, a typical corotation lag of the order of 5 to 10\% below L ~ 2.6, as well as a slight radial transport of the order of 20 m s-1. The magnetic local time dependence of the electric drift is consistent with that of the ionosphere wind dynamo below L ~ 2 and with that of a solar wind-driven convection electric field above L ~ 2. A secondary longitudinal dependence of the electric field is also found. Therefore, this work also demonstrates that the instruments on board Van Allen Probes are able to perform accurate measurements of the electric drift below L ~ 3. Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023613 electric drift; electric field; Inner radiation belt; plasmasphere; subcorotation; Van Allen Probes |
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The electric drift E \texttimes B/B2 plays a fundamental role for the description of plasma flow and particle acceleration. Yet it is not well-known in the inner belt and slot region because of a lack of reliable in situ measurements. In this article, we present an analysis of the electric drifts measured below L ~ 3 by both Van Allen Probes A and B from September 2012 to December 2014. The objective is to determine the typical components of the equatorial electric drift in both radial and azimuthal directions. The dependences of the components on radial distance, magnetic local time, and geographic longitude are examined. The results from Van Allen Probe A agree with Van Allen Probe B. They show, among other things, a typical corotation lag of the order of 5 to 10\% below L ~ 2.6, as well as a slight radial transport of the order of 20 m s-1. The magnetic local time dependence of the electric drift is consistent with that of the ionosphere wind dynamo below L ~ 2 and with that of a solar wind-driven convection electric field above L ~ 2. A secondary longitudinal dependence of the electric field is also found. Therefore, this work also demonstrates that the instruments on board Van Allen Probes are able to perform accurate measurements of the electric drift below L ~ 3. Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023613 electric drift; electric field; Inner radiation belt; plasmasphere; subcorotation; Van Allen Probes |
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We present Van Allen Probe observation of drift-resonance interaction between energetic electrons and ultra-low frequency (ULF) waves on October 29, 2013. Oscillations in electron flux were observed at the period of \~450s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (\~50 to 150 keV) across the estimated resonant energy (\~104 keV) is \~360\textdegree. This phase relationship is different from the characteristic 180\textdegree phase shift as expected from the drift-resonance theory. We speculate that the additional 180\textdegree phase difference arises from the inversion of electron phase space density (PSD) gradient, which in turn is caused by the drift motion of the substorm injected electrons. This PSD gradient adjusts the characteristic particle signatures in the drift-resonance theory, which indicates a coupling effect between the magnetotail and the radiation belt and helps to better understand the wave-particle interaction in the magnetosphere. Chen, X.-R.; Zong, Q.-G.; Zhou, X.-Z.; Blake, Bernard; Wygant, John; Kletzing, Craig; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071252 drift-resonance; injection; PSD gradient; ULF waves; Van Allen Probes |
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We present Van Allen Probe observation of drift-resonance interaction between energetic electrons and ultra-low frequency (ULF) waves on October 29, 2013. Oscillations in electron flux were observed at the period of \~450s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (\~50 to 150 keV) across the estimated resonant energy (\~104 keV) is \~360\textdegree. This phase relationship is different from the characteristic 180\textdegree phase shift as expected from the drift-resonance theory. We speculate that the additional 180\textdegree phase difference arises from the inversion of electron phase space density (PSD) gradient, which in turn is caused by the drift motion of the substorm injected electrons. This PSD gradient adjusts the characteristic particle signatures in the drift-resonance theory, which indicates a coupling effect between the magnetotail and the radiation belt and helps to better understand the wave-particle interaction in the magnetosphere. Chen, X.-R.; Zong, Q.-G.; Zhou, X.-Z.; Blake, Bernard; Wygant, John; Kletzing, Craig; Published by: Geophysical Research Letters Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016GL071252 drift-resonance; injection; PSD gradient; ULF waves; Van Allen Probes |
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Prompt recovery of MeV electron populations in the post-storm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly non-linear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant non-adiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of non-linear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy 100s keV - 3 MeV can be accelerated by 50 keV - 200 keV in resonant interactions with a single VLF rising tone on a time scale of 10-100 msec. Foster, J.; Erickson, P.; Omura, Y.; Baker, D.; Kletzing, C.; Claudepierre, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023429 nonlinear acceleration; Radiation belt; Van Allen Probes; VLF chorus; wave particle interactions |
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Prompt recovery of MeV electron populations in the post-storm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly non-linear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant non-adiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of non-linear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy 100s keV - 3 MeV can be accelerated by 50 keV - 200 keV in resonant interactions with a single VLF rising tone on a time scale of 10-100 msec. Foster, J.; Erickson, P.; Omura, Y.; Baker, D.; Kletzing, C.; Claudepierre, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023429 nonlinear acceleration; Radiation belt; Van Allen Probes; VLF chorus; wave particle interactions |
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Prompt recovery of MeV electron populations in the post-storm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly non-linear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant non-adiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of non-linear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy 100s keV - 3 MeV can be accelerated by 50 keV - 200 keV in resonant interactions with a single VLF rising tone on a time scale of 10-100 msec. Foster, J.; Erickson, P.; Omura, Y.; Baker, D.; Kletzing, C.; Claudepierre, S.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2016 YEAR: 2016 DOI: 10.1002/2016JA023429 nonlinear acceleration; Radiation belt; Van Allen Probes; VLF chorus; wave particle interactions |
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Characteristic energy range of electron scattering due to plasmaspheric hiss We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth\textquoterights inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth\textquoterights outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4\textendash200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L = 2\textendash6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2-D Fokker-Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV\textendash1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles. Ma, Q.; Li, W.; Thorne, R.; Bortnik, J.; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Baker, D.; Blake, J.; Fennell, J.; Claudepierre, S.; Angelopoulos, V.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2016 YEAR: 2016 DOI: 10.1002/2016JA023311 electron flux decay; pitch angle scattering; Plasmaspheric Hiss; Van Allen Probes; Van Allen Probes observation |
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Characteristic energy range of electron scattering due to plasmaspheric hiss We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth\textquoterights inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth\textquoterights outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4\textendash200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L = 2\textendash6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2-D Fokker-Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV\textendash1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles. Ma, Q.; Li, W.; Thorne, R.; Bortnik, J.; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Baker, D.; Blake, J.; Fennell, J.; Claudepierre, S.; Angelopoulos, V.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2016 YEAR: 2016 DOI: 10.1002/2016JA023311 electron flux decay; pitch angle scattering; Plasmaspheric Hiss; Van Allen Probes; Van Allen Probes observation |
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Characteristic energy range of electron scattering due to plasmaspheric hiss We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth\textquoterights inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth\textquoterights outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4\textendash200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L = 2\textendash6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2-D Fokker-Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV\textendash1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles. Ma, Q.; Li, W.; Thorne, R.; Bortnik, J.; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Baker, D.; Blake, J.; Fennell, J.; Claudepierre, S.; Angelopoulos, V.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2016 YEAR: 2016 DOI: 10.1002/2016JA023311 electron flux decay; pitch angle scattering; Plasmaspheric Hiss; Van Allen Probes; Van Allen Probes observation |
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Characteristic energy range of electron scattering due to plasmaspheric hiss We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth\textquoterights inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth\textquoterights outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4\textendash200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L = 2\textendash6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2-D Fokker-Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV\textendash1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles. Ma, Q.; Li, W.; Thorne, R.; Bortnik, J.; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Baker, D.; Blake, J.; Fennell, J.; Claudepierre, S.; Angelopoulos, V.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2016 YEAR: 2016 DOI: 10.1002/2016JA023311 electron flux decay; pitch angle scattering; Plasmaspheric Hiss; Van Allen Probes; Van Allen Probes observation |
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The loss of protons in the outer part of the inner radiation belt (L = 2 to 3) during the 17 March 2015 geomagnetic storm was investigated using test particle simulations that follow full Lorentz trajectories with both magnetic and electric fields calculated from an empirical model. The simulation results presented here are compared with proton pitch angle measurements from the Van Allen Probe satellites Relativistic Electron Proton Telescope (REPT) instrument before and after the coronal mass ejection-shock-driven storm of 17\textendash18 March 2015, with minimum Dst =- 223 nT, the strongest storm of Solar Cycle 24, for four different energy ranges with 30, 38, 50, and 66 MeV mean energies. Two simulations have been run, one with an inductive electric field and one without. All four energy channels show good agreement with the Van Allen Probes REPT measurements for low L (L < 2.4) in both simulations but diverge for higher L values. The inclusion of the inductive electric field, calculated from the time-changing magnetic field, significantly improves the agreement between simulation and REPT measurements at L > 2.4. A previous study using the Highly Elliptical Orbiter 3 spacecraft also showed improved agreement when including the inductive electric field but was unable to compare effects on the pitch angle distributions. Engel, M.; Kress, B.; Hudson, M.; Selesnick, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2016 YEAR: 2016 DOI: 10.1002/2016JA023333 field line curvature scattering; inductive electric field; proton loss; Radiation belt; Van Allen Probes |