Electron heating in high Mach number collisionless shocks

TL;DR

This paper introduces a new theoretical model for electron heating in high Mach number collisionless shocks, emphasizing the role of differential particle inertia and microturbulence, aligning with kinetic simulations.

Contribution

The model explains electron heating via inertia differences and microturbulence effects, providing a self-consistent approach validated by simulations.

Findings

Efficient electron heating occurs through differential scattering and electric fields.

The model aligns with kinetic simulation results.

Heating mechanism is driven by Weibel instability-generated magnetic fields.

Abstract

The energy partition in high Mach number collisionless shock waves is central to a wide range of high-energy astrophysical environments. We present a new theoretical model for electron heating that accounts for the energy exchange between electrons and ions at the shock. The fundamental mechanism relies on the difference in inertia between electrons and ions, resulting in differential scattering of the particles off a decelerating magnetically-dominated microturbulence across the shock transition. We show that the self-consistent interplay between the resulting ambipolar-type electric field and diffusive transport of electrons leads to efficient heating in the magnetic field produced by the Weibel instability in the high-Mach number regime and is consistent with fully kinetic simulations.