论文标题
准平行冲击中的随机和准绝热电子加热
Stochastic and quasi-adiabatic electron heating in quasi-parallel shocks
论文作者
论文摘要
Using Magnetospheric Multiscale (MMS) observations at the Earth's quasi-parallel bow shock we demonstrate that electrons are heated by two different mechanisms: a quasi-adiabatic heating process during magnetic field compression, characterized by the isotropic temperature relation $T/B=(T_0/B_0)(B_0/B)^α$ with $α=2/3$ when the electron heating function $ |χ_e| <1 $，以及$ |χ_e|> 1 $时的随机加热过程。这两个过程均由随机加热函数的值$χ_j= m_j q_j^{ - 1} b^{ - 2} \ Mathrm {div}（\ Mathbf {e} _ \ perp）粒子中的粒子$ $ m_j $和电费$ q_j $ and Mather＆Mathers $ and Mathbf $ \ mathbf {b} $。测试粒子模拟用于表明研究冲击中的随机电子加热和加速度是通过频率（0.4-5）的波（0.4-5）$ f_ {ce} $（Electron gyrofquerquency）用于散装加热的，而波浪$ f> 5 \，F> 5 \，F_，F_，F_ {CE} $，用于加速该分布功能的尾部。随机加热会引起平顶电子分布功能，经常在冲击附近观察到。还表明，电子回旋器漂移（ECD）的倾斜极化电场和离子声学不稳定性将电子散落到平行方向上，并保持电子分布的各向同性。本文报告的结果可能与行星际冲击和其他天体物理冲击的电子加热和加速有关。
Using Magnetospheric Multiscale (MMS) observations at the Earth's quasi-parallel bow shock we demonstrate that electrons are heated by two different mechanisms: a quasi-adiabatic heating process during magnetic field compression, characterized by the isotropic temperature relation $T/B=(T_0/B_0)(B_0/B)^α$ with $α=2/3$ when the electron heating function $|χ_e|<1$, and a stochastic heating process when $|χ_e|>1$. Both processes are controlled by the value of the stochastic heating function $χ_j = m_j q_j^{-1} B^{-2}\mathrm{div}(\mathbf{E}_\perp)$ for particles with mass $m_j$ and charge $q_j$ in the electric and magnetic fields $\mathbf{E}$ and $\mathbf{B}$. Test particle simulations are used to show that the stochastic electron heating and acceleration in the studied shock is accomplished by waves at frequencies (0.4 - 5) $f_{ce}$ (electron gyrofrequency) for bulk heating, and waves $f>5\,f_{ce}$ for acceleration of the tail of the distribution function. Stochastic heating can give rise to flat-top electron distribution functions, frequently observed near shocks. It is also shown that obliquely polarized electric fields of electron cyclotron drift (ECD) and ion acoustic instabilities scatter the electrons into the parallel direction and keep the isotropy of the electron distribution. The results reported in this paper may be relevant to electron heating and acceleration at interplanetary shocks and other astrophysical shocks.
