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Found 2758 entries in the Bibliography.
Showing entries from 751 through 800
| 2019 |
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Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field-aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of <=10 keV protons. For >10 keV protons, the field-aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Our results suggest that the wave normal distribution of electromagnetic ion cyclotron waves plays an important role in the pitch angle evolution and scattering loss of ring current protons and should be incorporated in future global modeling of ring current dynamics. Cao, Xing; Ni, Binbin; Summers, Danny; Shprits, Yuri; Gu, Xudong; Fu, Song; Lou, Yuequn; Zhang, Yang; Ma, Xin; Zhang, Wenxun; Huang, He; Yi, Juan; Published by: Geophysical Research Letters Published on: 01/2019 YEAR: 2019 DOI: 10.1029/2018GL081550 EMIC waves; Quasi-linear diffusion; Ring current protons; Van Allen Probes; wave-particle interactions |
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To understand the relationship between generation of electromagnetic ion cyclotron (EMIC) waves and energetic particle injections, we performed a statistical study of EMIC waves associated with and without injections based on the Van Allen Probes (Radiation Belt Storm Probes) and Geostationary Operational Environmental Satellite (GOES; GOES-13 and GOES-15) observations. Using 47 months of observations, we identified wave events seen by the Van Allen Probes relative to the plasmapause and to energetic particle injections seen by GOES-13 and GOES-15 on the nightside. We separated the events into four categories: EMIC waves with (without) injections inside (outside) the plasmasphere. We found that He+ EMIC waves have higher occurrence rate inside the plasmasphere, while H+ EMIC waves predominantly occur outside the plasmasphere. Meanwhile, the time duration and peak occurrence rate of EMIC waves associated with injections are shorter and limited to a narrower magnetic local time region than those without injections, indicating that these waves have localized source regions. He+ EMIC waves inside the plasmasphere associated with injection are usually accompanied by an increase in H+ flux within energies of 1\textendash50 keV through all magnetic local time regions, while most wave events outside the plasmasphere show less relationship with H+ flux increase. From these observations, we suggest that injected hot ions are the major driver of He+ EMIC waves inside the plasmasphere during active time. Expanding plasmasphere during quiet times can provide broad wave source regions for He+ EMIC waves on the dayside. However, H+ EMIC waves outside the plasmasphere show different characteristics, suggesting that these waves are generated by other processes. Jun, C.-W.; Yue, C.; Bortnik, J.; Lyons, L.; Nishimura, Y.; Kletzing, C.; Wygant, J.; Spence, H.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2019 YEAR: 2019 DOI: 10.1029/2018JA025886 EMIC waves associated with and without injections; Relationship between EMIC wave activity and energetic H+ flux variation; Simultaneous observations using the Van Allen Probes and GOES satellites; Spatial occurrence distributions of EMIC waves; Van Allen Probes |
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To understand the relationship between generation of electromagnetic ion cyclotron (EMIC) waves and energetic particle injections, we performed a statistical study of EMIC waves associated with and without injections based on the Van Allen Probes (Radiation Belt Storm Probes) and Geostationary Operational Environmental Satellite (GOES; GOES-13 and GOES-15) observations. Using 47 months of observations, we identified wave events seen by the Van Allen Probes relative to the plasmapause and to energetic particle injections seen by GOES-13 and GOES-15 on the nightside. We separated the events into four categories: EMIC waves with (without) injections inside (outside) the plasmasphere. We found that He+ EMIC waves have higher occurrence rate inside the plasmasphere, while H+ EMIC waves predominantly occur outside the plasmasphere. Meanwhile, the time duration and peak occurrence rate of EMIC waves associated with injections are shorter and limited to a narrower magnetic local time region than those without injections, indicating that these waves have localized source regions. He+ EMIC waves inside the plasmasphere associated with injection are usually accompanied by an increase in H+ flux within energies of 1\textendash50 keV through all magnetic local time regions, while most wave events outside the plasmasphere show less relationship with H+ flux increase. From these observations, we suggest that injected hot ions are the major driver of He+ EMIC waves inside the plasmasphere during active time. Expanding plasmasphere during quiet times can provide broad wave source regions for He+ EMIC waves on the dayside. However, H+ EMIC waves outside the plasmasphere show different characteristics, suggesting that these waves are generated by other processes. Jun, C.-W.; Yue, C.; Bortnik, J.; Lyons, L.; Nishimura, Y.; Kletzing, C.; Wygant, J.; Spence, H.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2019 YEAR: 2019 DOI: 10.1029/2018JA025886 EMIC waves associated with and without injections; Relationship between EMIC wave activity and energetic H+ flux variation; Simultaneous observations using the Van Allen Probes and GOES satellites; Spatial occurrence distributions of EMIC waves; Van Allen Probes |
| 2018 |
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With observations of Van Allen Probe A, in this letter we display a typical event where banded whistler waves shifted up their frequencies with frequency bands broadening as a response to the enhancement of solar wind dynamic pressure. Meanwhile, the anisotropy of electrons with energies about several tens of keV was observed to increase. Through the comparison of the calculated wave growth rates and observed wave spectral intensity, we suggest that those banded whistler waves observed with frequencies shifted up and frequency bands broadening could be locally excited by these hot electrons with increased anisotropy. The current study provides a great in situ evidence for the influence on frequencies of banded whistler waves by the enhancement of solar wind dynamic pressures, which reveals the important role of solar wind dynamic pressures playing in the frequency properties of banded whistler waves. Yu, Xiongdong; Yuan, Zhigang; Li, Haimeng; Huang, Shiyong; Wang, Dedong; Yao, Fei; Funsten, H.; Wygant, J.; Published by: Geophysical Research Letters Published on: Mar-08-2020 YEAR: 2018 DOI: 10.1029/2018GL078849 Banded whistler-mode waves; Frequency properties; inner magnetosphere; solar wind dynamic pressure; Van Allen Probes |
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The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle dependent inner belt core (L~<2.2 and E<700 keV), pitch-angle homogeneous outer belt low-energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch-angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for α0~<60\textdegree, E>100 keV, 3.5 Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; Drozdov, A; Villa, J.; Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; Ukhorskiy, A; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA026111 electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions |
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The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle dependent inner belt core (L~<2.2 and E<700 keV), pitch-angle homogeneous outer belt low-energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch-angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for α0~<60\textdegree, E>100 keV, 3.5 Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; Drozdov, A; Villa, J.; Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; Ukhorskiy, A; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA026111 electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions |
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The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle dependent inner belt core (L~<2.2 and E<700 keV), pitch-angle homogeneous outer belt low-energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch-angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for α0~<60\textdegree, E>100 keV, 3.5 Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; Drozdov, A; Villa, J.; Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; Ukhorskiy, A; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA026111 electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions |
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The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle dependent inner belt core (L~<2.2 and E<700 keV), pitch-angle homogeneous outer belt low-energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch-angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for α0~<60\textdegree, E>100 keV, 3.5 Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; Drozdov, A; Villa, J.; Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; Ukhorskiy, A; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA026111 electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions |
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The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle dependent inner belt core (L~<2.2 and E<700 keV), pitch-angle homogeneous outer belt low-energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch-angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for α0~<60\textdegree, E>100 keV, 3.5 Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; Drozdov, A; Villa, J.; Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; Ukhorskiy, A; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA026111 electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions |
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The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch-angle (α0) is analyzed during the calm 11-day interval (March 4 \textendashMarch 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)-regions persist through 11 days of hiss wave scattering; the pitch-angle dependent inner belt core (L~<2.2 and E<700 keV), pitch-angle homogeneous outer belt low-energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch-angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for α0~<60\textdegree, E>100 keV, 3.5 Ripoll, -F.; Loridan, V.; Denton, M.; Cunningham, G.; Reeves, G.; ik, O.; Fennell, J.; Turner, D.; Drozdov, A; Villa, J.; Shprits, Y; Thaller, S.; Kurth, W.; Kletzing, C.; Henderson, M.; Ukhorskiy, A; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA026111 electron lifetime; hiss waves; pitch-angle diffusion coefficient; Radiation belts; Van Allen Probes; wave particle interactions |
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Gyroresonant wave-particle interactions with very low frequency whistler mode chorus waves can accelerate subrelativistic seed electrons (hundreds of keV) to relativistic energies in the outer radiation belt during geomagnetic storms. In this study, we conduct a superposed epoch analysis of the chorus wave activity, the seed electron development, and the outer radiation belt electron response between L* = 2.5 and 5.5, for 25 coronal mass ejection and 35 corotating interaction region storms using Van Allen Probes observations. Electron data from the Magnetic Electron Ion Spectrometer and Relativistic Electron Proton Telescope instruments are used to monitor the storm-phase development of the seed and relativistic electrons, and magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science instrument are used to identify the chorus wave activity. Our results show a deeper (lower L*), stronger (higher flux), and earlier (epoch time) average seed electron enhancement and a resulting greater average radiation belt electron enhancement in coronal mass ejection storms compared to the corotating interaction region storms despite similar levels and lifetimes of average chorus wave activity for the two storm drivers. The earlier and deeper seed electron enhancement during the coronal mass ejection storms, likely driven by greater convection and substorm activity, provides a higher probability for local acceleration. These results emphasize the importance of the timing and the level of the seed electron enhancements in radiation belt dynamics. Bingham, S.; Mouikis, C.; Kistler, L.; Boyd, A.; Paulson, K.; Farrugia, C.; Huang, C.; Spence, H.; Claudepierre, S.; Kletzing, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA025963 CIR storms; CME storms; Radiation belts; seed electrons; Van Allen Probes; VLF waves |
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Gyroresonant wave-particle interactions with very low frequency whistler mode chorus waves can accelerate subrelativistic seed electrons (hundreds of keV) to relativistic energies in the outer radiation belt during geomagnetic storms. In this study, we conduct a superposed epoch analysis of the chorus wave activity, the seed electron development, and the outer radiation belt electron response between L* = 2.5 and 5.5, for 25 coronal mass ejection and 35 corotating interaction region storms using Van Allen Probes observations. Electron data from the Magnetic Electron Ion Spectrometer and Relativistic Electron Proton Telescope instruments are used to monitor the storm-phase development of the seed and relativistic electrons, and magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science instrument are used to identify the chorus wave activity. Our results show a deeper (lower L*), stronger (higher flux), and earlier (epoch time) average seed electron enhancement and a resulting greater average radiation belt electron enhancement in coronal mass ejection storms compared to the corotating interaction region storms despite similar levels and lifetimes of average chorus wave activity for the two storm drivers. The earlier and deeper seed electron enhancement during the coronal mass ejection storms, likely driven by greater convection and substorm activity, provides a higher probability for local acceleration. These results emphasize the importance of the timing and the level of the seed electron enhancements in radiation belt dynamics. Bingham, S.; Mouikis, C.; Kistler, L.; Boyd, A.; Paulson, K.; Farrugia, C.; Huang, C.; Spence, H.; Claudepierre, S.; Kletzing, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA025963 CIR storms; CME storms; Radiation belts; seed electrons; Van Allen Probes; VLF waves |
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Gyroresonant wave-particle interactions with very low frequency whistler mode chorus waves can accelerate subrelativistic seed electrons (hundreds of keV) to relativistic energies in the outer radiation belt during geomagnetic storms. In this study, we conduct a superposed epoch analysis of the chorus wave activity, the seed electron development, and the outer radiation belt electron response between L* = 2.5 and 5.5, for 25 coronal mass ejection and 35 corotating interaction region storms using Van Allen Probes observations. Electron data from the Magnetic Electron Ion Spectrometer and Relativistic Electron Proton Telescope instruments are used to monitor the storm-phase development of the seed and relativistic electrons, and magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science instrument are used to identify the chorus wave activity. Our results show a deeper (lower L*), stronger (higher flux), and earlier (epoch time) average seed electron enhancement and a resulting greater average radiation belt electron enhancement in coronal mass ejection storms compared to the corotating interaction region storms despite similar levels and lifetimes of average chorus wave activity for the two storm drivers. The earlier and deeper seed electron enhancement during the coronal mass ejection storms, likely driven by greater convection and substorm activity, provides a higher probability for local acceleration. These results emphasize the importance of the timing and the level of the seed electron enhancements in radiation belt dynamics. Bingham, S.; Mouikis, C.; Kistler, L.; Boyd, A.; Paulson, K.; Farrugia, C.; Huang, C.; Spence, H.; Claudepierre, S.; Kletzing, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2018 YEAR: 2018 DOI: 10.1029/2018JA025963 CIR storms; CME storms; Radiation belts; seed electrons; Van Allen Probes; VLF waves |
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Determination of the Equatorial Electron Differential Flux From Observations at Low Earth Orbit Variations in the high-energy relativistic electron flux of the radiation belts depend on transport, acceleration, and loss processes, and importantly on the lower-energy seed population. However, data on the seed population is limited to a few satellite missions. Here we present a new method that utilizes data from the Medium Energy Proton/Electron Detector on board the low-altitude Polar Operational Environmental Satellites to retrieve the seed population at a pitch angle of 90\textdegree. The integral flux values measured by Medium Energy Proton/Electron Detector relate to a low equatorial pitch angle and were converted to omnidirectional flux using parameters obtained from fitting one or two urn:x-wiley:jgra:media:jgra54628:jgra54628-math-0001 functions to pitch angle distributions given by three and a half years of Van Allen Probes data. Two methods to convert from integral to differential flux are explored. One utilizes integral and differential flux energy distributions from the AE9 model, the second employs an iterative fitting approach based on a Reverse Monte Carlo (RMC) method. The omnidirectional differential flux was converted to an equatorial pitch angle of 90\textdegree, again using statistical pitch angle distributions from Van Allen Probe data. We validate the resulting 90\textdegree flux for 100- to 600-keV electrons against measurements from the Van Allen Probes and show an average agreement within a factor of 4 for L* > 3.7. The resulting data set offers a high time resolution, across multiple magnetic local time planes, and may be used to formulate event-specific low-energy boundary conditions for radiation belt models. Allison, Hayley; Horne, Richard; Glauert, Sarah; Del Zanna, Giulio; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018JA025786 electrons; integral flux; Radiation belts; seed population; Van Allen Probes |
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Determination of the Equatorial Electron Differential Flux From Observations at Low Earth Orbit Variations in the high-energy relativistic electron flux of the radiation belts depend on transport, acceleration, and loss processes, and importantly on the lower-energy seed population. However, data on the seed population is limited to a few satellite missions. Here we present a new method that utilizes data from the Medium Energy Proton/Electron Detector on board the low-altitude Polar Operational Environmental Satellites to retrieve the seed population at a pitch angle of 90\textdegree. The integral flux values measured by Medium Energy Proton/Electron Detector relate to a low equatorial pitch angle and were converted to omnidirectional flux using parameters obtained from fitting one or two urn:x-wiley:jgra:media:jgra54628:jgra54628-math-0001 functions to pitch angle distributions given by three and a half years of Van Allen Probes data. Two methods to convert from integral to differential flux are explored. One utilizes integral and differential flux energy distributions from the AE9 model, the second employs an iterative fitting approach based on a Reverse Monte Carlo (RMC) method. The omnidirectional differential flux was converted to an equatorial pitch angle of 90\textdegree, again using statistical pitch angle distributions from Van Allen Probe data. We validate the resulting 90\textdegree flux for 100- to 600-keV electrons against measurements from the Van Allen Probes and show an average agreement within a factor of 4 for L* > 3.7. The resulting data set offers a high time resolution, across multiple magnetic local time planes, and may be used to formulate event-specific low-energy boundary conditions for radiation belt models. Allison, Hayley; Horne, Richard; Glauert, Sarah; Del Zanna, Giulio; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018JA025786 electrons; integral flux; Radiation belts; seed population; Van Allen Probes |
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Recent analysis of an event observed by the Van Allen Probes in the source region outside the plasmapause has shown that fast magnetosonic waves (also referred to as equatorial noise) propagate preferentially in the azimuthal direction, implying that wave amplification should occur during azimuthal propagation. To demonstrate this, we carry out 2-D particle-in-cell simulations of the fast magnetosonic mode at the dipole magnetic equator with the simulation box size, the magnetic field inhomogeneity, and the plasma parameters chosen from the same event recently analyzed. The self-consistently evolving electric and magnetic field fluctuations are characterized by spectral peaks at harmonics of the local proton cyclotron frequency. The azimuthal component of the electric field fluctuations is larger than the radial component, indicating wave propagation mainly along the azimuthal direction. Because the simulation box is within the source region, this also implies wave amplification mainly during azimuthal propagation. The excellent agreement between the wave polarization properties of the present simulations and the recently reported observations is clear evidence that the main wave amplification occurs during azimuthal propagation in the source region. Min, Kyungguk; Boardsen, Scott; Denton, Richard; Liu, Kaijun; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018JA026037 2D particle-in-cell simulation; Fast Magnetosonic Waves; Perpendicular propagation; Van Allen Probes |
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Recent analysis of an event observed by the Van Allen Probes in the source region outside the plasmapause has shown that fast magnetosonic waves (also referred to as equatorial noise) propagate preferentially in the azimuthal direction, implying that wave amplification should occur during azimuthal propagation. To demonstrate this, we carry out 2-D particle-in-cell simulations of the fast magnetosonic mode at the dipole magnetic equator with the simulation box size, the magnetic field inhomogeneity, and the plasma parameters chosen from the same event recently analyzed. The self-consistently evolving electric and magnetic field fluctuations are characterized by spectral peaks at harmonics of the local proton cyclotron frequency. The azimuthal component of the electric field fluctuations is larger than the radial component, indicating wave propagation mainly along the azimuthal direction. Because the simulation box is within the source region, this also implies wave amplification mainly during azimuthal propagation. The excellent agreement between the wave polarization properties of the present simulations and the recently reported observations is clear evidence that the main wave amplification occurs during azimuthal propagation in the source region. Min, Kyungguk; Boardsen, Scott; Denton, Richard; Liu, Kaijun; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018JA026037 2D particle-in-cell simulation; Fast Magnetosonic Waves; Perpendicular propagation; Van Allen Probes |
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Electromagnetic whistler-mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave-particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum-frequency and difference-frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly-generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH waves by hot electron instabilities, the nonlinear wave-wave interactions could additionally redistribute energy among the resonant waves, potentially affecting to some extent the magnetospheric electron dynamics. Gao, Zhonglei; Su, Zhenpeng; Xiao, Fuliang; Summers, Danny; Liu, Nigang; Zheng, Huinan; Wang, Yuming; Wei, Fengsi; Wang, Shui; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080635 aurora; Chorus wave; electron cyclotron harmonic wave; nonlinear wave-wave interaction; Radiation belt; Van Allen Probes |
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Electromagnetic whistler-mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave-particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum-frequency and difference-frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly-generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH waves by hot electron instabilities, the nonlinear wave-wave interactions could additionally redistribute energy among the resonant waves, potentially affecting to some extent the magnetospheric electron dynamics. Gao, Zhonglei; Su, Zhenpeng; Xiao, Fuliang; Summers, Danny; Liu, Nigang; Zheng, Huinan; Wang, Yuming; Wei, Fengsi; Wang, Shui; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080635 aurora; Chorus wave; electron cyclotron harmonic wave; nonlinear wave-wave interaction; Radiation belt; Van Allen Probes |
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In this letter, we present unique conjugated satellite observations of MeV relativistic electron precipitation caused by electromagnetic ion cyclotron (EMIC) waves. On the outer boundary of the plasmasphere, the Van Allen probe observed EMIC waves. At ionospheric altitudes, the NOAA 16 satellite at the footprint of Van Allen probe simultaneously detected obvious flux enhancements for precipitating >MeV radiation belt electrons, but not for precipitating Yuan, Zhigang; Liu, Kun; Yu, Xiongdong; Yao, Fei; Huang, Shiyong; Wang, Dedong; Ouyang, Zhihai; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080481 Chorus; EMIC waves; Particle precipitation; Radiation belt; ring current; Van Allen Probes; Wave-particle interaction |
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In this letter, we present unique conjugated satellite observations of MeV relativistic electron precipitation caused by electromagnetic ion cyclotron (EMIC) waves. On the outer boundary of the plasmasphere, the Van Allen probe observed EMIC waves. At ionospheric altitudes, the NOAA 16 satellite at the footprint of Van Allen probe simultaneously detected obvious flux enhancements for precipitating >MeV radiation belt electrons, but not for precipitating Yuan, Zhigang; Liu, Kun; Yu, Xiongdong; Yao, Fei; Huang, Shiyong; Wang, Dedong; Ouyang, Zhihai; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080481 Chorus; EMIC waves; Particle precipitation; Radiation belt; ring current; Van Allen Probes; Wave-particle interaction |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground-based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground-based observations constrained spatial-temporal variations of the EMIC wave activity during the loss event. Multi-satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantially decreased within a few tens of minutes where the EMIC waves were present. The present study provides an observational estimate of the loss time scale of MeV electrons by EMIC waves. Kurita, S.; Miyoshi, Y.; Shiokawa, K.; Higashio, N.; Mitani, T.; Takashima, T.; Matsuoka, A.; Shinohara, I.; Kletzing, C.; Blake, J.; Claudepierre, S.; Connors, M.; Oyama, S.; Nagatsuma, T.; Sakaguchi, K.; Baishev, D.; Otsuka, Y.; Published by: Geophysical Research Letters Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018GL080262 EMIC waves; loss; PWING project; Radiation belt; The Arase satellite; Van Allen Probes |
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Simulations of Van Allen Probes Plasmaspheric Electron Density Observations We simulate equatorial plasmaspheric electron densities using a physics-based model (Cold PLasma, CPL; used in the ring current-atmosphere interactions model) of the source and loss processes of refilling and erosion driven by empirical inputs. The performance of CPL is evaluated against in situ measurements by the Van Allen Probes (Radiation Belt Storm Probes) for two events: the 31 May to 5 June and 15 to 20 January 2013 geomagnetic storms observed in the premidnight and postmidnight magnetic local time (MLT) sectors, respectively. Overall, CPL reproduces the radial extent of the plasmasphere to within a mean absolute difference of urn:x-wiley:jgra:media:jgra54637:jgra54637-math-0001 L. The model electric field responsible for E \texttimes B convection and the parameterization of geomagnetic conditions (under the Kp-index and solar wind properties) implemented by CPL did not account for localized enhancements in the duskward electric field during increased activity. Rather, it was found to be largely dependent on the measure of the quiet time background. This property indicates that the agreement between these simulations and observations does not account for the complete set of physical processes during extreme (strong or weak) geomagnetic conditions impacting the plasmasphere. Nevertheless, at the presented resolution of the model CPL does provide good agreement in reproducing Radiation Belt Storm Probes observations of plasmaspheric density and plasmapause location. De Pascuale, S.; Jordanova, V.; Goldstein, J.; Kletzing, C.; Kurth, W.; Thaller, S.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018JA025776 convection; observations; plasmasphere; RBSP; simulation; Van Allen Probes |
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Simulations of Van Allen Probes Plasmaspheric Electron Density Observations We simulate equatorial plasmaspheric electron densities using a physics-based model (Cold PLasma, CPL; used in the ring current-atmosphere interactions model) of the source and loss processes of refilling and erosion driven by empirical inputs. The performance of CPL is evaluated against in situ measurements by the Van Allen Probes (Radiation Belt Storm Probes) for two events: the 31 May to 5 June and 15 to 20 January 2013 geomagnetic storms observed in the premidnight and postmidnight magnetic local time (MLT) sectors, respectively. Overall, CPL reproduces the radial extent of the plasmasphere to within a mean absolute difference of urn:x-wiley:jgra:media:jgra54637:jgra54637-math-0001 L. The model electric field responsible for E \texttimes B convection and the parameterization of geomagnetic conditions (under the Kp-index and solar wind properties) implemented by CPL did not account for localized enhancements in the duskward electric field during increased activity. Rather, it was found to be largely dependent on the measure of the quiet time background. This property indicates that the agreement between these simulations and observations does not account for the complete set of physical processes during extreme (strong or weak) geomagnetic conditions impacting the plasmasphere. Nevertheless, at the presented resolution of the model CPL does provide good agreement in reproducing Radiation Belt Storm Probes observations of plasmaspheric density and plasmapause location. De Pascuale, S.; Jordanova, V.; Goldstein, J.; Kletzing, C.; Kurth, W.; Thaller, S.; Wygant, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2018 YEAR: 2018 DOI: 10.1029/2018JA025776 convection; observations; plasmasphere; RBSP; simulation; Van Allen Probes |
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Shortly after the launch of the Van Allen Probes, a new three-belt configuration of the electron radiation belts was reported. Using data between September 2012 and November 2017, we have identified 30 three-belt events and found that about 18\% of geomagnetic storms result in such configuration. Based on the identified events, we evaluated some characteristics of the remnant (intermediate) belt. We determined the energy range of occurrence and found it peaks at E = 5.2 MeV. We also determined that the magnetopause location and SYM-H value may play an important role in the outer belt losses that lead to formation and location of the remnant belt. Finally, we calculated the decay rates of the remnant belt for all events and found that their lifetime gets longer as energy increases, ranging from days at E = 1.8 MeV up to months at E = 6.3 MeV suggesting that remnant belts are extremely persistent. Pinto, V\; Bortnik, Jacob; Moya, Pablo; Lyons, Larry; Sibeck, David; Kanekal, Shrikanth; Spence, Harlan; Baker, Daniel; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080274 Belt Formation; MeV Electrons; Outer Belt; Radiation belts; Remnant Belt; Three Belts; Van Allen Probes |
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Shortly after the launch of the Van Allen Probes, a new three-belt configuration of the electron radiation belts was reported. Using data between September 2012 and November 2017, we have identified 30 three-belt events and found that about 18\% of geomagnetic storms result in such configuration. Based on the identified events, we evaluated some characteristics of the remnant (intermediate) belt. We determined the energy range of occurrence and found it peaks at E = 5.2 MeV. We also determined that the magnetopause location and SYM-H value may play an important role in the outer belt losses that lead to formation and location of the remnant belt. Finally, we calculated the decay rates of the remnant belt for all events and found that their lifetime gets longer as energy increases, ranging from days at E = 1.8 MeV up to months at E = 6.3 MeV suggesting that remnant belts are extremely persistent. Pinto, V\; Bortnik, Jacob; Moya, Pablo; Lyons, Larry; Sibeck, David; Kanekal, Shrikanth; Spence, Harlan; Baker, Daniel; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080274 Belt Formation; MeV Electrons; Outer Belt; Radiation belts; Remnant Belt; Three Belts; Van Allen Probes |
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Shortly after the launch of the Van Allen Probes, a new three-belt configuration of the electron radiation belts was reported. Using data between September 2012 and November 2017, we have identified 30 three-belt events and found that about 18\% of geomagnetic storms result in such configuration. Based on the identified events, we evaluated some characteristics of the remnant (intermediate) belt. We determined the energy range of occurrence and found it peaks at E = 5.2 MeV. We also determined that the magnetopause location and SYM-H value may play an important role in the outer belt losses that lead to formation and location of the remnant belt. Finally, we calculated the decay rates of the remnant belt for all events and found that their lifetime gets longer as energy increases, ranging from days at E = 1.8 MeV up to months at E = 6.3 MeV suggesting that remnant belts are extremely persistent. Pinto, V\; Bortnik, Jacob; Moya, Pablo; Lyons, Larry; Sibeck, David; Kanekal, Shrikanth; Spence, Harlan; Baker, Daniel; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080274 Belt Formation; MeV Electrons; Outer Belt; Radiation belts; Remnant Belt; Three Belts; Van Allen Probes |
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Shortly after the launch of the Van Allen Probes, a new three-belt configuration of the electron radiation belts was reported. Using data between September 2012 and November 2017, we have identified 30 three-belt events and found that about 18\% of geomagnetic storms result in such configuration. Based on the identified events, we evaluated some characteristics of the remnant (intermediate) belt. We determined the energy range of occurrence and found it peaks at E = 5.2 MeV. We also determined that the magnetopause location and SYM-H value may play an important role in the outer belt losses that lead to formation and location of the remnant belt. Finally, we calculated the decay rates of the remnant belt for all events and found that their lifetime gets longer as energy increases, ranging from days at E = 1.8 MeV up to months at E = 6.3 MeV suggesting that remnant belts are extremely persistent. Pinto, V\; Bortnik, Jacob; Moya, Pablo; Lyons, Larry; Sibeck, David; Kanekal, Shrikanth; Spence, Harlan; Baker, Daniel; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080274 Belt Formation; MeV Electrons; Outer Belt; Radiation belts; Remnant Belt; Three Belts; Van Allen Probes |
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Electron flux measurements are an important diagnostic for interactions between ultralow-frequency (ULF) waves and relativistic (\~1 MeV) electrons. Since measurements are collected by particle detectors with finite energy channel width, they are affected by a phase mixing process that can obscure these interactions. We demonstrate that ultrahigh-resolution electron measurements from the Magnetic Electron Ion Spectrometer on the Van Allen Probes mission\textemdashobtained using a data product that improves the energy resolution by roughly an order of magnitude\textemdashare crucial for understanding ULF wave-particle interactions. In particular, the ultrahigh-resolution measurements reveal a range of complex dynamics that cannot be resolved by standard measurements. Furthermore, the standard measurements provide estimates for the ULF flux modulation amplitude, period, and phase that may not be representative of true flux modulations, potentially leading to ambiguous conclusions concerning electron dynamics. Hartinger, M.; Claudepierre, S.; Turner, D.; Reeves, G.; Breneman, A.; Mann, I.; Peek, T.; Chang, E.; Blake, J.; Fennell, J.; O\textquoterightBrien, T.; Looper, M.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080291 drift resonance; particle detector; Pc5; Radiation belts; ULF wave; Van Allen Probes; Wave-particle interaction |
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Electron flux measurements are an important diagnostic for interactions between ultralow-frequency (ULF) waves and relativistic (\~1 MeV) electrons. Since measurements are collected by particle detectors with finite energy channel width, they are affected by a phase mixing process that can obscure these interactions. We demonstrate that ultrahigh-resolution electron measurements from the Magnetic Electron Ion Spectrometer on the Van Allen Probes mission\textemdashobtained using a data product that improves the energy resolution by roughly an order of magnitude\textemdashare crucial for understanding ULF wave-particle interactions. In particular, the ultrahigh-resolution measurements reveal a range of complex dynamics that cannot be resolved by standard measurements. Furthermore, the standard measurements provide estimates for the ULF flux modulation amplitude, period, and phase that may not be representative of true flux modulations, potentially leading to ambiguous conclusions concerning electron dynamics. Hartinger, M.; Claudepierre, S.; Turner, D.; Reeves, G.; Breneman, A.; Mann, I.; Peek, T.; Chang, E.; Blake, J.; Fennell, J.; O\textquoterightBrien, T.; Looper, M.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080291 drift resonance; particle detector; Pc5; Radiation belts; ULF wave; Van Allen Probes; Wave-particle interaction |
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Fine structure of whistler-mode hiss in plasmaspheric plumes observed by the Van Allen Probes We survey 3 years (2013-2015) of data from the Van Allen Probes related to plasmaspheric plume crossing events. We detect 194 plume crossing events, and we find that 97\% of the plumes are accompanied by VLF hiss emissions. The plumes are mainly detected on the duskside or dayside. Careful examination of the hiss spectra reveals that all hiss emissions consist of obvious fine structure. Application of a band pass filter reveals that the fine structure is consistent with the occurrence of discrete wave packets. The hiss data display high coherency. The events are classified by location. Dusk side hiss and night side hiss tend to have extremely high polarization with no chorus at the high-frequency end of the dynamic spectrum. The dusk side hiss has a distinct upper frequency limit. On the other hand, the dawn side hiss has strong chorus elements at the upper hiss frequency which makes the upper frequency limit ambiguous. We show that the structure of whistler-mode hiss is different from artificial random noise. Although noise also has fine spectral characteristics, the polarization and waveform data are totally different from the hiss cases. Our results strongly suggest that whistle-mode hiss in plasmaspheric plumes universally possesses fine structure. Nakamura, S.; Omura, Y.; Summers, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA025803 fine structure; hiss; nonlinear; plasmaspheric plume; Van Allen Probes |
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Generation of EMIC Waves Observed by Van Allen Probes at Low L Shells Observation of linearly polarized He+-band electromagnetic ion cyclotron (EMIC) waves at low L shells is a new, and quite unexpected, result from the Van Allen Probes mission. Here we analyze the two EMIC wave events observed by Van Allen Probes at low L shells and put forward a new-generation mechanism for the low-L EMIC waves. Both events were observed at L \~ 3 but one of them has a discrete spectrum near the O+ gyrofrequency and its second harmonic, whereas the second event has a broad spectrum between the O+ gyrofrequency and its second harmonic. For both events, the major conclusions of our analysis can be summarized as follows. (1) Only O+ causes EMIC wave generation, and instability is driven by the positive derivatives of distribution functions over perpendicular component of velocity. (2) The timing and frequencies of generated waves are in agreement with observations. The generated wave normal angles, however, are highly oblique being in strong disagreement with the minimum variance angles obtained from Fast Fourier transform. (3) The wave step analysis shows that a signal nonstationarity is not a major cause for disagreement between the minimum variance angles and theoretical predictions for normal angles. (4) A superposition of plane sine waves with the same frequency and normal angle but with different azimuthal angles for wave vector around the background magnetic field can reconcile the polarization properties of EMIC waves obtained from Fast Fourier transform and/or the wave step analysis with those predicted by the linear theory of EMIC waves. Gamayunov, Konstantin; Min, Kyungguk; Saikin, Anthony; Rassoul, Hamid; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA025629 effects of wave superposition on EMIC waves; EMIC wave generation; EMIC waves at low L shells; growth rate calculations for EMIC waves; polarization properties of EMIC waves; Van Allen Probes; Van Allen Probes observations at low L shells |
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Generation of EMIC Waves Observed by Van Allen Probes at Low L Shells Observation of linearly polarized He+-band electromagnetic ion cyclotron (EMIC) waves at low L shells is a new, and quite unexpected, result from the Van Allen Probes mission. Here we analyze the two EMIC wave events observed by Van Allen Probes at low L shells and put forward a new-generation mechanism for the low-L EMIC waves. Both events were observed at L \~ 3 but one of them has a discrete spectrum near the O+ gyrofrequency and its second harmonic, whereas the second event has a broad spectrum between the O+ gyrofrequency and its second harmonic. For both events, the major conclusions of our analysis can be summarized as follows. (1) Only O+ causes EMIC wave generation, and instability is driven by the positive derivatives of distribution functions over perpendicular component of velocity. (2) The timing and frequencies of generated waves are in agreement with observations. The generated wave normal angles, however, are highly oblique being in strong disagreement with the minimum variance angles obtained from Fast Fourier transform. (3) The wave step analysis shows that a signal nonstationarity is not a major cause for disagreement between the minimum variance angles and theoretical predictions for normal angles. (4) A superposition of plane sine waves with the same frequency and normal angle but with different azimuthal angles for wave vector around the background magnetic field can reconcile the polarization properties of EMIC waves obtained from Fast Fourier transform and/or the wave step analysis with those predicted by the linear theory of EMIC waves. Gamayunov, Konstantin; Min, Kyungguk; Saikin, Anthony; Rassoul, Hamid; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA025629 effects of wave superposition on EMIC waves; EMIC wave generation; EMIC waves at low L shells; growth rate calculations for EMIC waves; polarization properties of EMIC waves; Van Allen Probes; Van Allen Probes observations at low L shells |
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High-frequency thermal fluctuations and instabilities in the radiation belt environment This paper overviews the electrostatic and electromagnetic theories of spontaneous emission in magnetized plasma as they relate to measured electric and magnetic field fluctuations in quiet time radiation belt and ring current region. The pervasively detected high-frequency fluctuations in the upper-hybrid frequency range as well as the background low-frequency range spectral profile in the whistler mode range are explained within the context of the spontaneous emission theory. The quasilinear calculation of loss-cone instability is also carried out in order to validate the assumption of spontaneous emission model. It is shown that the saturated wave amplitudes associated with the upper-hybrid and multiple-harmonic cyclotron instability are quite low, indicating that the theoretical explanation based upon the assumption of spontaneous emission theory may be adequate for understanding the observed background fluctuations during quiet times. Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA025643 loss cone instability; Radiation belt; spontaneous emission; upper hybrid wave; Van Allen Probes |
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Impact of Background Magnetic Field for EMIC Wave-Driven Electron Precipitation Wave-particle interaction between relativistic electrons and electromagnetic ion cyclotron (EMIC) waves is a highly debated loss process contributing to the dynamics of Earth\textquoterights radiation belts. Theoretical studies show that EMIC waves can result in strong loss of relativistic electrons in the radiation belts (Summers \& Thorne, 2003, https://doi.org/10.1029/2002JA009489). However, many of these studies have not been validated by observations. Li et al. (2014, https://doi.org/10.1002/2014GL062273) modeled the relativistic electron precipitation observed by Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) in a single-event case study based on a quasi-linear diffusion model and observations by Van Allen Probes and GOES 13. We expand upon that study to investigate the localization of the precipitation region and the effectiveness of EMIC waves as an electron loss mechanism.The model results of BARREL 1I observations on 17 January 2013 show that as the BARREL balloon drifts in local time to regions that map to lower equatorial magnetic field strength, the flux of precipitating electrons increases and peaks at lower energy. The hypothesis that the energy of the precipitating electrons is controlled by background magnetic field strength is further tested by considering observations from balloon campaigns conducted from 2000 to 2014, including BARREL. Consistent with theory for wave-particle interaction between relativistic electrons and EMIC waves, we find observationally that stronger equatorial magnetic field strength generally correlates with more energetic electron precipitation and further conclude that magnetic field strength can drive the localization and distribution of precipitating electrons. Woodger, L.; Millan, R.; Li, Z.; Sample, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA025315 electron precipitation; EMIC waves; Radiation belts; Van Allen Probes |
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Using Van Allen Probes\textquoteright observations and established plasmapause location (Lpp) models, we investigate the relationship between the location of the initial enhancement (IE) of energetic electrons and the innermost (among all magnetic local time sectors) Lpp over five intense storm periods. Our study reveals that the IE events for 30 keV to 2MeV electrons always occurred outside of the innermost Lpp. On average, the inner extent of the IE events (LIE) for <800 keV electrons was closer to the innermost Lpp when compared to the LIE for >800 keV electrons that was found consistently at ~1.5 RE outside of the innermost Lpp. The IE of 10s keV electrons was observed before the IE of 100s keV electrons, and the IE of >800 keV electrons was observed on average 12.6\textpm2.3 hours after the occurrence of the earliest IE event. In addition, we report an overall electron (~30 keV to ~2 MeV) flux increase outside the plasmasphere during the selected storm periods, in contrast to the little change of energy spectrum evolution inside the plasmasphere; this demonstrates the important role of the plasmasphere in shaping energetic electron dynamics. Our investigation of the LIE-Lpp relationship also provides insights into the underlying physical processes responsible for the dynamics of tens keV to >MeV electrons. Khoo, Leng; Li, Xinlin; Zhao, Hong; Sarris, Theodore; Xiang, Zheng; Zhang, Kun; Kellerman, Adam; Blake, Bernard; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA026074 energetic electron; enhancements; plasmasphere; Radiation belt; Van Allen Probes |
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Using Van Allen Probes\textquoteright observations and established plasmapause location (Lpp) models, we investigate the relationship between the location of the initial enhancement (IE) of energetic electrons and the innermost (among all magnetic local time sectors) Lpp over five intense storm periods. Our study reveals that the IE events for 30 keV to 2MeV electrons always occurred outside of the innermost Lpp. On average, the inner extent of the IE events (LIE) for <800 keV electrons was closer to the innermost Lpp when compared to the LIE for >800 keV electrons that was found consistently at ~1.5 RE outside of the innermost Lpp. The IE of 10s keV electrons was observed before the IE of 100s keV electrons, and the IE of >800 keV electrons was observed on average 12.6\textpm2.3 hours after the occurrence of the earliest IE event. In addition, we report an overall electron (~30 keV to ~2 MeV) flux increase outside the plasmasphere during the selected storm periods, in contrast to the little change of energy spectrum evolution inside the plasmasphere; this demonstrates the important role of the plasmasphere in shaping energetic electron dynamics. Our investigation of the LIE-Lpp relationship also provides insights into the underlying physical processes responsible for the dynamics of tens keV to >MeV electrons. Khoo, Leng; Li, Xinlin; Zhao, Hong; Sarris, Theodore; Xiang, Zheng; Zhang, Kun; Kellerman, Adam; Blake, Bernard; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018JA026074 energetic electron; enhancements; plasmasphere; Radiation belt; Van Allen Probes |
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Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00\textendash07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9\textendash5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15\% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10\textendash07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus. e, M.; Matsuoka, A.; Kumamoto, A.; Kasahara, Y.; Goldstein, J.; Teramoto, M.; Tsuchiya, F.; Matsuda, S.; Shoji, M.; Imajo, S.; Oimatsu, S.; Yamamoto, K.; Obana, Y.; Nomura, R.; Fujimoto, A.; Shinohara, I.; Miyoshi, Y.; Kurth, W.; Kletzing, C.; Smith, C.; MacDowall, R.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080122 Arase satellite; Geomagnetic storm; inner magnetosphere; oxygen torus; simultaneous observation; Van Allen Probes; Van Allen Probes satellite |
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Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00\textendash07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9\textendash5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15\% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10\textendash07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus. e, M.; Matsuoka, A.; Kumamoto, A.; Kasahara, Y.; Goldstein, J.; Teramoto, M.; Tsuchiya, F.; Matsuda, S.; Shoji, M.; Imajo, S.; Oimatsu, S.; Yamamoto, K.; Obana, Y.; Nomura, R.; Fujimoto, A.; Shinohara, I.; Miyoshi, Y.; Kurth, W.; Kletzing, C.; Smith, C.; MacDowall, R.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080122 Arase satellite; Geomagnetic storm; inner magnetosphere; oxygen torus; simultaneous observation; Van Allen Probes; Van Allen Probes satellite |
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Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00\textendash07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9\textendash5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15\% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10\textendash07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus. e, M.; Matsuoka, A.; Kumamoto, A.; Kasahara, Y.; Goldstein, J.; Teramoto, M.; Tsuchiya, F.; Matsuda, S.; Shoji, M.; Imajo, S.; Oimatsu, S.; Yamamoto, K.; Obana, Y.; Nomura, R.; Fujimoto, A.; Shinohara, I.; Miyoshi, Y.; Kurth, W.; Kletzing, C.; Smith, C.; MacDowall, R.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080122 Arase satellite; Geomagnetic storm; inner magnetosphere; oxygen torus; simultaneous observation; Van Allen Probes; Van Allen Probes satellite |
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Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00\textendash07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9\textendash5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15\% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10\textendash07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus. e, M.; Matsuoka, A.; Kumamoto, A.; Kasahara, Y.; Goldstein, J.; Teramoto, M.; Tsuchiya, F.; Matsuda, S.; Shoji, M.; Imajo, S.; Oimatsu, S.; Yamamoto, K.; Obana, Y.; Nomura, R.; Fujimoto, A.; Shinohara, I.; Miyoshi, Y.; Kurth, W.; Kletzing, C.; Smith, C.; MacDowall, R.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080122 Arase satellite; Geomagnetic storm; inner magnetosphere; oxygen torus; simultaneous observation; Van Allen Probes; Van Allen Probes satellite |
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Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00\textendash07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9\textendash5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15\% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10\textendash07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus. e, M.; Matsuoka, A.; Kumamoto, A.; Kasahara, Y.; Goldstein, J.; Teramoto, M.; Tsuchiya, F.; Matsuda, S.; Shoji, M.; Imajo, S.; Oimatsu, S.; Yamamoto, K.; Obana, Y.; Nomura, R.; Fujimoto, A.; Shinohara, I.; Miyoshi, Y.; Kurth, W.; Kletzing, C.; Smith, C.; MacDowall, R.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080122 Arase satellite; Geomagnetic storm; inner magnetosphere; oxygen torus; simultaneous observation; Van Allen Probes; Van Allen Probes satellite |
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Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00\textendash07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9\textendash5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15\% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10\textendash07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus. e, M.; Matsuoka, A.; Kumamoto, A.; Kasahara, Y.; Goldstein, J.; Teramoto, M.; Tsuchiya, F.; Matsuda, S.; Shoji, M.; Imajo, S.; Oimatsu, S.; Yamamoto, K.; Obana, Y.; Nomura, R.; Fujimoto, A.; Shinohara, I.; Miyoshi, Y.; Kurth, W.; Kletzing, C.; Smith, C.; MacDowall, R.; Published by: Geophysical Research Letters Published on: 10/2018 YEAR: 2018 DOI: 10.1029/2018GL080122 Arase satellite; Geomagnetic storm; inner magnetosphere; oxygen torus; simultaneous observation; Van Allen Probes; Van Allen Probes satellite |