Electron Heating in Perpendicular Low-Beta Shocks. (arXiv:2002.11132v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Tran_A/0/1/0/all/0/1">Aaron Tran</a>, <a href="http://arxiv.org/find/physics/1/au:+Sironi_L/0/1/0/all/0/1">Lorenzo Sironi</a>

Collisionless shocks heat electrons in the solar wind, interstellar blast
waves, and hot gas permeating galaxy clusters. How much shock heating goes to
electrons instead of ions, and what plasma physics controls electron heating?
We simulate 2-D perpendicular shocks with a fully kinetic particle-in-cell
code. For magnetosonic Mach number $mathcal{M}_mathrm{ms} sim 1$-$10$ and
plasma beta $beta_mathrm{p} lesssim 4$, the post-shock electron/ion
temperature ratio $T_mathrm{e}/T_mathrm{i}$ decreases from $1$ to $0.1$ with
increasing $mathcal{M}_mathrm{ms}$. In a representative
$mathcal{M}_mathrm{ms}=3.1$, $beta_mathrm{p}=0.25$ shock, electrons heat
above adiabatic compression in two steps: ion-scale $E_parallel = vec{E}
cdot hat{b}$ accelerates electrons into streams along $vec{B}$, which then
relax via two-stream-like instability. Shock rippling also allows quasi-static
shock-normal electric fields to heat electrons; we find that quasi-static
fields generally contribute half of the electron heating beyond adiabatic
compression.

Collisionless shocks heat electrons in the solar wind, interstellar blast
waves, and hot gas permeating galaxy clusters. How much shock heating goes to
electrons instead of ions, and what plasma physics controls electron heating?
We simulate 2-D perpendicular shocks with a fully kinetic particle-in-cell
code. For magnetosonic Mach number $mathcal{M}_mathrm{ms} sim 1$-$10$ and
plasma beta $beta_mathrm{p} lesssim 4$, the post-shock electron/ion
temperature ratio $T_mathrm{e}/T_mathrm{i}$ decreases from $1$ to $0.1$ with
increasing $mathcal{M}_mathrm{ms}$. In a representative
$mathcal{M}_mathrm{ms}=3.1$, $beta_mathrm{p}=0.25$ shock, electrons heat
above adiabatic compression in two steps: ion-scale $E_parallel = vec{E}
cdot hat{b}$ accelerates electrons into streams along $vec{B}$, which then
relax via two-stream-like instability. Shock rippling also allows quasi-static
shock-normal electric fields to heat electrons; we find that quasi-static
fields generally contribute half of the electron heating beyond adiabatic
compression.

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