Signatures of Ultrarelativistic Electron Loss in the Heart of the Outer Radiation Belt Measured by Van Allen Probes

Aseev, Nikita; Shprits, Y. Y.; Drozdov, Alexander; Kellerman, Adam; Usanova, Maria; Wang, Dedong; Zhelavskaya, Irina

doi:10.1002/2017ja024485

Cited by 36 publications

(62 citation statements)

References 53 publications

(76 reference statements)

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“…Left-hand polarized EMIC waves resonate predominantly with low pitch angle relativistic electrons (Summers et al, 2007a(Summers et al, , 2007b, producing characteristic pitch angles distributions with clear bite-outs at smaller pitch angles. That is, the particles with large pitch angle are less affected, so that at relatively low energies (up to about 1 or 2 MeV), the bulk of the distribution function may be relatively unaffected (Usanova et al, 2014; though see Aseev et al, 2017). In some cases, transport by higher-frequency whistler mode hiss or chorus waves, in combination with EMIC waves, can help facilitate decrease in the distribution function at all pitch angles Li et al, 2007;Shprits et al, 2009Shprits et al, , 2017Shprits et al, , 2018.…”

Section: 1029/2018ja026384mentioning

confidence: 99%

“…That is, the particles with large pitch angle are less affected, so that at relatively low energies (up to about 1 or 2 MeV), the bulk of the distribution function may be relatively unaffected (Usanova et al, ; though see Aseev et al, ). In some cases, transport by higher‐frequency whistler mode hiss or chorus waves, in combination with EMIC waves, can help facilitate decrease in the distribution function at all pitch angles (Aseev et al, ; Li et al, ; Shprits et al, , , ). But the simulations we will be using to examine pitch angle scattering do not include the high‐frequency waves, so the pitch angle scattering studied in this paper results entirely from the EMIC waves.…”

Section: Introductionmentioning

confidence: 99%

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Pitch Angle Scattering of Sub‐MeV Relativistic Electrons by Electromagnetic Ion Cyclotron Waves

et al. 2019

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Electromagnetic ion cyclotron (EMIC) waves have long been considered to be a significant loss mechanism for relativistic electrons. This has most often been attributed to resonant interactions with the highest amplitude waves. But recent observations have suggested that the dominant energy of electrons precipitated to the atmosphere may often be relatively low, less than 1 MeV, whereas the minimum resonant energy of the highest amplitude waves is often greater than 2 MeV. Here we use relativistic electron test particle simulations in the wavefields of a hybrid code simulation of EMIC waves in dipole geometry in order to show that significant pitch angle scattering can occur due to interaction with low‐amplitude short‐wavelength EMIC waves. In the case we examined, these waves are in the H band (at frequencies above the He+ gyrofrequency), even though the highest amplitude waves were in the He band frequency range (below the He+ gyrofrequency). We also present wave power distributions for 29 EMIC simulations in straight magnetic field line geometry that show that the high wave number portion of the spectrum is in every case mostly due to the H band waves. Though He band waves are often associated with relativistic electron precipitation, it is possible that the He band waves do not directly scatter the sub‐megaelectron volts (sub‐MeV) electrons, but that the presence of He band waves is associated with high plasma density which lowers the minimum resonant energy so that these electrons can more easily resonate with the H band waves.

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Section: 1029/2018ja026384mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pitch Angle Scattering of Sub‐MeV Relativistic Electrons by Electromagnetic Ion Cyclotron Waves

et al. 2019

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“…In reality, both processes are likely important and contribute differently on a case-by-case basis. Considering that perspective, it is important look for telltale signatures of both loss processes using guidelines established by previous studies (e.g., Aseev et al, 2017;Shprits et al, 2017;Turner et al, 2014;Xiang et al, 2017).…”

Section: Sea Of Mlt-dependent >100-kev Electron Fluxesmentioning

confidence: 99%

“…However, the cost of such high‐quality scientific platforms limits the number which will operate at any given time. In recent years there has been a wealth of exceptional in situ observations deepening our understanding (e.g., Aseev et al, ; Jaynes et al, ; Kasahara et al, ; Turner et al, ; Xiang et al, ; Zhao et al, ) but which are limited in their ability to provide simultaneous MLT and L coverage.…”

Section: Introductionmentioning

confidence: 99%

“…However, the cost of such high-quality scientific platforms limits the number which will operate at any given time. In recent years there has been a wealth of exceptional in situ observations deepening our understanding (e.g., Aseev et al, 2017;Jaynes et al, 2015;Kasahara et al, 2018;Turner et al, 2019;Xiang et al, 2018;Zhao et al, 2017) but which are limited in their ability to provide simultaneous MLT and L coverage. This is an area in which spacecraft with more limited instrumentation in LEO can assist, as they already exist as constellations of multiple satellites simultaneously monitoring different MLTs while rapidly moving through L-shells.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Local Time‐Resolved Examination of Radiation Belt Dynamics during High‐Speed Solar Wind Speed‐Triggered Substorm Clusters

Rodger

Turner

Clilverd

et al. 2019

Geophysical Research Letters

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Particle observations from low Earth orbiting satellites are used to undertake superposed epoch analysis around clusters of substorms, in order to investigate radiation belt dynamical responses to mild geomagnetic disturbances. Medium energy electrons and protons have drift periods long enough to discriminate between processes occurring at different magnetic local time, such as magnetopause shadowing, plasma wave activity, and substorm injections. Analysis shows that magnetopause shadowing produces clear loss in proton and electron populations over a wide range of L‐shells, initially on the dayside, which interacts with nightside substorm‐generated flux enhancements following charge‐dependent drift directions. Inner magnetospheric injections recently identified as an important source of tens to hundreds keV electrons at low L (L<3), occurring during similar solar wind‐driving conditions as recurrent substorms, show similar but more enhanced geomagnetic AU‐index signatures. Twofold increases in substorm occurrence at the time of the sudden particle enhancements at low L shells (SPELLS) suggest a common linkage.

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Storm-time depletions of multi-MeV radiation belt electrons observed at different pitch angles

Drozdov

Aseev

Effenberger

et al. 2019

Preprint

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During geomagnetic storms, the rapid depletion of the high‐energy (several MeV) outer radiation belt electrons is the result of loss to the interplanetary medium through the magnetopause, outward radial diffusion, and loss to the atmosphere due to wave‐particle interactions. We have performed a statistical study of 110 storms using pitch angle resolved electron flux measurements from the Van Allen Probes mission and found that inside of the radiation belt (L* = 3 − 5) the number of storms that result in depletion of electrons with equatorial pitch angle αeq = 30∘ is higher than number of storms that result in depletion of electrons with equatorial pitch angle αeq = 75∘. We conclude that this result is consistent with electron scattering by whistler and electromagnetic ion cyclotron waves. At the outer edge of the radiation belt (L* ≥ 5.2) the number of storms that result in depletion is also large (~40–50%), emphasizing the significance of the magnetopause shadowing effect and outward radial transport.

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Signatures of Ultrarelativistic Electron Loss in the Heart of the Outer Radiation Belt Measured by Van Allen Probes

Cited by 36 publications

References 53 publications

Pitch Angle Scattering of Sub‐MeV Relativistic Electrons by Electromagnetic Ion Cyclotron Waves

Pitch Angle Scattering of Sub‐MeV Relativistic Electrons by Electromagnetic Ion Cyclotron Waves

Magnetic Local Time‐Resolved Examination of Radiation Belt Dynamics during High‐Speed Solar Wind Speed‐Triggered Substorm Clusters

Storm-time depletions of multi-MeV radiation belt electrons observed at different pitch angles

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