Observations during the main phase of geomagnetic storms reveal an anticorrelation between the occurrence of broadband low-frequency electromagnetic waves and outer radiation belt electron flux. We show that the drift-bounce motion of electrons in the magnetic field of these waves leads to rapid electron transport. For observed spectral energy densities it is demonstrated that the wave magnetic field can drive radial diffusion via drift-bounce resonance on time scales less than a drift orbit. This process may provide outward transport sufficient to account for electron “dropouts” during storm main phase and more generally modulate the outer radiation belt during geomagnetic storms.
Bibliographical noteFunding Information:
This research was supported by NASA grants NNX15AF57G, NNX16AG69G, NNX17AD36G, and NNX17AI55G and Van Allen Probes (RBSP) funding provided under NASA prime contract NAS5-01072, including the EFW and EMFISIS investigations under JHU/APL contract 921647 and RBSP-ECT under JHU/APL contract 967399. Data generated from theoretical models are stored on Linux workstations at the Space Sciences Laboratory at UC Berkeley and can be accessed by contacting the first author. Van Allen Probes measurements used in this study can be obtained from the following data repositories: EFW http:// www.space.umn.edu/rbspefw-data/, EMFISIS http://emfisis.physics.uiowa. edu/data/index, and HOPE/MAGEIS/ REPT https://www.rbsp-ect.lanl.gov/ science/DataDirectories.php and/or by directly contacting the first author.
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- Alfven waves
- geomagnetic storms
- radial transport
- radiation belts