Department of Physics, University of Helsinki, Post Office Box 64, FI-00014 Helsinki, Finland.
Phys Rev Lett. 2009 Dec 11;103(24):245001. doi: 10.1103/PhysRevLett.103.245001. Epub 2009 Dec 9.
The downstream region of a collisionless quasiparallel shock is structured containing bulk flows with high kinetic energy density from a previously unidentified source. We present Cluster multispacecraft measurements of this type of supermagnetosonic jet as well as of a weak secondary shock front within the sheath, that allow us to propose the following generation mechanism for the jets: The local curvature variations inherent to quasiparallel shocks can create fast, deflected jets accompanied by density variations in the downstream region. If the speed of the jet is super(magneto)sonic in the reference frame of the obstacle, a second shock front forms in the sheath closer to the obstacle. Our results can be applied to collisionless quasiparallel shocks in many plasma environments.
碰撞非平行激波的下游区域结构中包含来自先前未识别源的具有高动能密度的体流。我们展示了Cluster 多航天器对这种超磁声速射流以及鞘内弱二次前缘的测量，这使我们能够提出射流的以下生成机制：准平行激波固有的局部曲率变化可以产生快速的、偏转的射流，并伴随着下游区域的密度变化。如果射流在障碍物参考系中的速度是超（磁声）速的，那么在更靠近障碍物的鞘内会形成第二个前缘。我们的结果可以应用于许多等离子体环境中的碰撞非平行激波。
