太阳风中磁场重联离子扩散区的大尺度特征

利用ACE和WIND卫星2007年1月6日的联合探测, 在1AU附近发现了一个等离子体密度极低的Petschek-like重联喷流区. 该喷流区内部出现了非常明显的Hall双极磁场、等离子体密度下降区以及与Hall电流相符的低能段电子投掷角分布. 这些特征与重联离子扩散区的Hall效应非常吻合, 说明很可能在太阳风中观测到了一个离子扩散区. 分析表明, 与之相关的磁场重联为准稳态快速完全反向重联, 其扩散区以一对慢模波为边界, 空间尺度达到80个离子惯性长度, 表现出了大尺度重联的特征. 

Characteristics of Reconnection Diffusion Region in the Solar Wind

A Petschek-like reconnection exhaust of extremely low plasma density was detected by ACE and WIND on 6 January 2007 near 1AU in the solar wind. The exhaust is characterized by an apparent Hall bipolar magnetic field, ion and electron density depletion layers and pitch angle distribution of low energy electrons anti-parallel to the direction of Hall current. Such features indicate a possible reconnection ion diffusion region in the solar wind. To the best of our knowledge, this is the first time to report direct detections of ion diffusion region associated with solar wind reconnection exhaust. Observations show that the associated reconnection is quasi-steady, almost anti-parallel merging (no guide field) and fast with a dimensionless reconnection rate of about 2%. Meanwhile, the diffusion region is bounded by a pair of slow-mode waves and the spatial width is up to 80 ion inertial lengths, performing large-scale characteristics of reconnection for large systems.