Direct evidence of nonstationary collisionless shocks in space plasmas.
Direct evidence of nonstationary collisionless shocks in space plasmas.
复制标题
空间等离子体中非平稳无碰撞冲击的直接证据。
DOI：
10.1126/sciadv.aau9926
复制
发表时间：
2019
期刊：
影响因子：
13.6
通讯作者：
Dimmock AP
中科院分区：
文献类型：
--
作者：
Dimmock AP
无碰撞激波在整个宇宙中无处不在：围绕恒星、超新星遗迹、活动星系核、双星系统、彗星和行星。关键信息是由高马赫数无碰撞冲击加速的粒子的电磁辐射携带的。这些冲击本质上是非平稳的，粒子加速的特征物理尺度仍然未知。量化这些尺度是至关重要的，因为它影响到重新分配上游等离子体动能到其他自由度的基本过程，特别是电子热化。对非定常激波动力学的直接现场测量还没有报道。因此，最能描述这一过程的模型仍然是未知的。在这里，我们提出了直接的证据表明，过渡到非平稳性与电子尺度的场结构内的冲击斜坡。
Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom—particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.