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Electron Bulk Acceleration and Thermalization at Earth's Quasiperpendicular Bow Shock
L-J Chen1,2, S Wang1,2, L B Wilson1
1NASA, Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
Physical Review Letters
|June 16, 2018
Summary
A new electron heating process at Earth's bow shock accelerates solar wind electrons via an electric field pulse and whistler-mode waves. This process is crucial for cross-shock electron heating.
Area of Science:
- Space Physics
- Plasma Physics
- Astrophysics
Background:
- Electron heating at quasiperpendicular bow shocks is traditionally attributed to electric potentials and wave-particle interactions.
- Previous models did not fully explain the observed electron heating mechanisms at the shock front.
Purpose of the Study:
- To identify and characterize a novel electron heating process at the leading edge of Earth's bow shock.
- To investigate the role of electric fields and wave-particle interactions in this new heating mechanism.
Main Methods:
- Observation of electron distribution functions using in-situ spacecraft measurements.
- Analysis of electric field pulses and whistler-mode waves.
- Investigation of nonlinear current-driven instabilities.
Main Results:
- Observed electron acceleration parallel to the magnetic field, exceeding electron thermal speed.
- Identified an electric field pulse within a whistler-mode wave as the primary acceleration driver.
- Demonstrated relaxation of high electron-ion drift via nonlinear instabilities, creating electron beams.
Conclusions:
- A new electron heating process involving parallel acceleration and nonlinear instability has been identified at the bow shock.
- This process, involving electron beams, is essential for understanding cross-shock electron heating.
- Findings challenge existing models and offer new insights into plasma dynamics at collisionless shocks.