NASA, Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
Department of Astronomy, University of Maryland, College Park, Maryland 20747, USA.
Phys Rev Lett. 2018 Jun 1;120(22):225101. doi: 10.1103/PhysRevLett.120.225101.
Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.
在地球的近垂直弓形激波处，电子加热被推测是由于准静态电势和通过波粒相互作用散射的综合影响。在这里，我们报告了观测到的电子分布函数，表明在激波前缘发生了一种新的电子加热过程。入射的太阳风电子沿磁场方向被加速到下游，达到超过电子热速度的电子-离子相对漂移速度。整体加速与嵌入在哨声模波中的电场脉冲有关。高电子-离子相对漂移主要通过非线性电流驱动不稳定性来松弛。松弛的分布中包含一个朝向激波的束流，这是加速电子的残余。类似的分布函数在整个激波过渡层中普遍存在，这表明观测到的加速和热化对于跨激波电子加热是至关重要的。
