磁云边界层中的重联慢激波观测分析

在Petschek模型中，排空区边界处的一对慢激波是能量耗散的重要机制.已有大量行星际空间的Petschek型磁场重联排空区观测事件被报道，但是只有少量的排空区边界处观测到了慢激波.针对一例位于磁云边界层中的Petschek型磁场重联排空区观测事件，在排空区靠近磁云一侧边界处证认了一例慢激波.激波跃变层两侧的磁场和等离子体参数满足Rankine-Hugoniot关系，且激波上下游的中间马赫数均小于1，上游的慢马赫数为2.94（>1），下游的慢马赫数为0.65（<1），符合慢激波的观测特征.磁云内部的等离子体β值很低，局地阿尔芬速度高，同时磁云边界层中可能发生丰富的磁场重联活动，这可能是磁云前边界处慢激波形成的原因. 

Observation of a Slow Shock Associated with Reconnection Exhaust inside the Boundary Layer of Magnetic Cloud at 1 AU

A pair of slow shocks in the Petschek reconnection model facilitate the energy transfer from magnetic field to kinetic and thermal energy of plasmas. In the past decade, a large amount of Petschek-like Reconnection Exhausts (RE) have been reported, but slow shocks bounding the REs are seldom identified. In this paper, a slow shock bounding a reconnection exhaust was identified in the front Boundary Layer (BL) of a Magnetic Cloud (MC) observed by WIND spacecraft on 27 February 2012. The observations of the jump conditions across the shock are in good agreement with the Rankine-Hugoniot relations. The intermediate Mach numbers are less than 1 on both sides of the shock. The slow Mach number is above unit (2.94) in the upstream side but below unit (0.65) in the downstream. The extremely low plasma beta (0.08) in the MC and the occurrence of magnetic reconnection in the MCBL may explain the formation of this slow shock.