A sharp dipolarization front(DF)has recently been detected in the Earth's magnetotail and is associated with complex kinetic effects.We present one event where a tailward propagating negative DF(with Bz decreasing...A sharp dipolarization front(DF)has recently been detected in the Earth's 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.展开更多
Recent studies show that the out-of-plane quadrupolar magnetic field in fast magnetic reconnection is distorted in the presence of a guide field. It is asymmetric with respect to the current sheet. In this work, we an...Recent studies show that the out-of-plane quadrupolar magnetic field in fast magnetic reconnection is distorted in the presence of a guide field. It is asymmetric with respect to the current sheet. In this work, we analyze the spatial and amplitude asymmetries of the Hall magnetic field By and the Hall electric field Ez in reconnection with different guide fields by a series of 2.5-D particle-in-cell simulations. We derive the relation between the asymmetry of By and Ez and the guide field strength. In addition, by analyzing the different terms in the generalized ohm＇s law, we find that the electric field Ez is mainly balanced by the Hall term, and the amplitude asymmetry is mainly caused by the Hall effect.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.41004060 and 40890163the Open Research Fund Program of the Key Laboratory of Space Weather,Chinese Academy of Sciencesthe Fundamental Research Funds for the Central Universities.
文摘A sharp dipolarization front(DF)has recently been detected in the Earth's 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.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41174147,41274170 and 41331070the Science Foundation of Jiangxi Province under Grant No 20142BCB23006
文摘Recent studies show that the out-of-plane quadrupolar magnetic field in fast magnetic reconnection is distorted in the presence of a guide field. It is asymmetric with respect to the current sheet. In this work, we analyze the spatial and amplitude asymmetries of the Hall magnetic field By and the Hall electric field Ez in reconnection with different guide fields by a series of 2.5-D particle-in-cell simulations. We derive the relation between the asymmetry of By and Ez and the guide field strength. In addition, by analyzing the different terms in the generalized ohm＇s law, we find that the electric field Ez is mainly balanced by the Hall term, and the amplitude asymmetry is mainly caused by the Hall effect.
