,Observation of a Sharp Negative Dipolarization Front in the Reconnection Outflow Region

• 作 者: ZHOU Meng HUANG Shi-Yong DENG Xiao-Hua PANG Ye
• 机 构: Institute of Space Science and Technology, Nanchang University, Nanchang 330031“,” Sate Key Laborato
• 出 处: 中国物理快报（英文版）
• 发表日期: 2011年10期

A sharp dipolarization front (DF) has recently been detected in the Earths magnetotail and is associated with complex kinetic effects.We present one event where a tailward propagating negative DF (with Bz decreasing sharply to negative value) was observed near a reconnection region.The thickness of the negative DF is comparable with the local ion gyro-radius/inertial length.There is a strong field-aligned current at the front.Electromagnetic whistler wave enhancements are observed around the front,associated with counter-streaming electron beams.We further compare the features of the observed negative DF with the recent kinetic simulation results,as well as the Earthward propagating DFs observed by the THEMIS spacecraft.A substorm is an explosive energy release process that occurs in the magnetosphere of many planets.Magnetic field dipolarization is believed to be an essential ingredient of the substorm process,each of which is generally associated with dipolarization.Traditionally,dipolarization was believed to be associated with a decrease in the cross-tail current in the nearEarth region,which might be caused by cross-tail current instability[1] or the dawnward inertial current due to fast-flow braking.[2]