Electron acceleration by Earth's bow shock: Wind observations
Abstract
We present a comprehensive study of in situ electron acceleration during 140 crossings of Earth's bow shock with good suprathermal electron observations by Wind 3DP instrument from 1995 through 2004. Among the selected 124 quasi-perpendicular (16 quasi-parallel) shock cases, ~91% (~44%), ~90% (~56%) and ~25% (~25%) show significant electron flux enhancements of JD/JA>1.5 across the shock, respectively at 0.43, 1.95, and 40 keV, where JDand JAare the electron flux in the shock's downstream and the ambient solar wind. For significantly shocked suprathermal electrons, the downstream flux JDas well as the flux enhancement JD/JApositively correlate most with the magnetic compression ratio rB, among the shock parameters. The downstream suprathermal electrons generally have three forms of spectra: a double power-law spectrum bending up at ~2 keV, a triple power-law spectrum bending up at ~2 keV then bending down at energies below 20 keV, and a double power-law spectrum bending down at energies between 2-20 keV. The first two forms of spectra generally retain the upward-bending shape of the ambient electron spectra, while the third spectral form appears to be unrelated with the ambient spectra. The downstream spectral index at ~0.5-2 keV (the flux enhancement JD/JAat ~0.5-6 keV) observed in the triple-power-law cases appears to be smaller (larger) than that observed in the upward-bending double-power-law cases and larger (smaller) than that observed in the downward-bending double-power-law cases, indicating that the triple power-law spectrum could be a transition form from the upward-bending to the downward-bending power law. The evolution of these three forms of electron spectra suggest that the stochastic shock drift acceleration may play a role in the electron acceleration at Earth's bow shock.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMSH0090011Y
- Keywords:
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- 7514 Energetic particles;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7807 Charged particle motion and acceleration;
- SPACE PLASMA PHYSICS;
- 7845 Particle acceleration;
- SPACE PLASMA PHYSICS;
- 7859 Transport processes;
- SPACE PLASMA PHYSICS