Thermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field-aligned pitch angle distributions

TitleThermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field-aligned pitch angle distributions
Publication TypeJournal Article
Year of Publication2015
AuthorsVasko, IY, Agapitov, OV, Mozer, FS, Artemyev, AV
JournalJournal of Geophysical Research: Space Physics
Date Published10/2015
Keywordsdouble layers; Fermi mechanism; field-aligned pitch angle distributions; outer radiation belt; thermal electron acceleration; Van Allen Probes
AbstractVan Allen Probes observations in the outer radiation belt have demonstrated an abundance of electrostatic electron-acoustic double layers (DL). DLs are frequently accompanied by field-aligned (bidirectional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV. We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e., due to reflections from DL potential humps. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism, electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher-energy electrons. It is shown that the Fermi mechanism can result in scattering into the loss cone of up to several tenths of percent of electrons with flux peaking at energies up to several hundred eVs.
URLhttp://doi.wiley.com/10.1002/2015JA021644http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021644
DOI10.1002/2015JA021644
Short TitleJ. Geophys. Res. Space Physics


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