Electron Flux Variability and Ultra‐Low Frequency Wave Activity in the Outer Radiation Belt Under the Influence of Interplanetary Coronal Mass Ejections and High‐Speed Solar Wind Streams: A Statistical Analysis From the Van Allen Probes Era

The ultra‐low frequency (ULF) waves can stochastically accelerate radiation belt electrons. Radial diffusion is a well‐established mechanism that can enhance or reduce the electron population in combination with other processes. Using data from the Van Allen Probes, we investigated the response of t...

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Bibliographic Details
Published in:	Journal of geophysical research. Space physics Vol. 127; no. 8
Main Authors:	Marchezi, J. P., Dai, L., Alves, L. R., Silva, L. A., Sibeck, D. G., Lago, A. Dal, Souza, V. M., Jauer, P. R., Veira, L. E. A., Cardoso, F. R., Deggeroni, V., Alves, M. V., Wang, C., Li, H., Liu, Z.
Format:	Journal Article
Language:	English
Published:	Washington Blackwell Publishing Ltd 01-08-2022
Subjects:	alfven waves Coronal mass ejection depletions Earth magnetosphere Electron flux enhancement Extremely low frequencies Fluctuations Frequency ranges geomagnetic pulsations Interplanetary magnetic field Jupiter Magnetic fields Outer radiation belt Probes Proton density (concentration) Protons Radiation Radiation belt electrons Radiation belts Reduction Solar corona Solar magnetic field Solar wind Solar wind structure Statistical analysis Streams ULF waves Waves
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Summary:	The ultra‐low frequency (ULF) waves can stochastically accelerate radiation belt electrons. Radial diffusion is a well‐established mechanism that can enhance or reduce the electron population in combination with other processes. Using data from the Van Allen Probes, we investigated the response of the 2.10 MeV energy electrons and ULF waves to two types of solar wind structures interacting with Earth's magnetosphere, namely, interplanetary coronal mass ejections (ICMEs) and High‐Speed solar wind streams (HSS). We use measured electron differential flux and ULF waves in the Pc4–Pc5 frequency range from October 2012 to May 2019. We examine 155 events with changes in the outer radiation belt electron differential flux. Results considering all ICMEs and HSSs during the Van Allen Probes era show that for both solar wind structures, solar wind interplanetary magnetic field Bz, solar wind proton density, and speed are related to the outer radiation belt relativistic electrons' response. The persistent ULF power is present during enhancement cases, while for reduction, the ULF waves power is concentrated at the initial reduction on the outer radiation belt electron flux. Key Points Interplanetary coronal mass ejections (ICMEs) related flux variation happens faster, while the High‐Speed solar wind streams (HSSs)‐related happens gradually, starting from higher to lower L* values Southward interplanetary magnetic field Bz, enhanced AE index, and high solar wind speed variations are commonly associated with flux enhancement Ultra‐low frequency diffusion coefficients are stronger and have a longer duration for enhancements than depletion during both ICME and HSS events
ISSN:	2169-9380 2169-9402
DOI:	10.1029/2021JA029887