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- Title
Realistic Electron Diffusion Rates and Lifetimes Due to Scattering by Electron Holes.
- Authors
Shen, Yangyang; Vasko, Ivan Y.; Artemyev, Anton; Malaspina, David M.; Chu, Xiangning; Angelopoulos, Vassilis; Zhang, Xiao‐Jia
- Abstract
Plasma sheet electron precipitation into the diffuse aurora is critical for magnetosphere‐ionosphere coupling. Recent studies have shown that electron phase space holes can pitch‐angle scatter electrons and may produce plasma sheet electron precipitation. These studies have assumed identical electron hole parameters to estimate electron scattering rates (Vasko et al., 2018, https://doi.org/10.1063/1.5039687). In this study, we have re‐evaluated the efficiency of this scattering by incorporating realistic electron hole properties from direct spacecraft observations into computing electron diffusion rates and lifetimes. The most important electron hole properties in this evaluation are their distributions in velocity and spatial scale and electric field root‐mean‐square intensity (Ew). Using direct measurements of electron holes during a plasma injection event observed by the Van Allen Probe at R∼6RE, we find that when Ew≥4 mV/m electron lifetimes can drop below 1 h and are mostly within strong diffusion limits at energies below ∼10 keV. During an injection observed by the THEMIS spacecraft at R∼12RE, electron holes with even typical intensities (Ew≥1 mV/m) can deplete low‐energy (<a few keV) plasma sheet electrons within tens of minutes following injections and convection from the tail. Our results confirm that electron holes are a significant contributor to plasma sheet electron precipitation during injections. Plain Language Summary: Recent studies have revealed that a class of nonlinear time domain structures, consisting mostly of electron phase space holes, which appear as broadband electrostatic emissions in the frequency domain, may pitch‐angle scatter plasma sheet electrons, producing diffuse auroral precipitation. Although how significantly electron holes contribute to the global diffuse aurora remains unclear, our study attempts to address the most fundamental question—what are realistic electron loss rates due to electron hole scattering in the terrestrial magnetosphere? Incorporating realistic electron hole distributions directly observed by various spacecraft missions into a newly developed methodology of calculating scattering rates, we have obtained realistic electron lifetimes for two injection events. In these events, broadband electrostatic emissions produced by electron holes are associated with sudden electron energy flux enhancements in the energy range of a few hundred eV up to more than 100 keV. The calculated electron lifetimes substantiate that electron holes play a significant role in generating low‐energy (less than a few keV) plasma sheet electron precipitation from the magnetotail following electron injections and convection. Although in the inner magnetosphere this electron hole induced precipitation is not as much as estimated from previous studies, appreciable precipitation can be produced by sufficiently intense electron holes which are not uncommon. Key Points: Realistic electron diffusion rates are computed by incorporating the observed electron hole distributionsElectron hole distributions in velocity and parallel scale and E‐field intensities control the scattering efficiencyRealistic lifetime estimates suggest efficient plasma sheet electron losses due to electron holes in plasma injections
- Subjects
ELECTRON precipitation; MAGNETOSPHERE; ELECTRON scattering; ELECTRIC fields; IONOSPHERE
- Publication
Journal of Geophysical Research. Space Physics, 2021, Vol 126, Issue 9, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2021JA029380