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
A three-dimensional(3-D)global hybrid simulation is carried out for the generation and structure of magnetic reconnection in the magnetosheath due to interaction of an interplanetary Tangential Discontinuity(TD)with t...A three-dimensional(3-D)global hybrid simulation is carried out for the generation and structure of magnetic reconnection in the magnetosheath due to interaction of an interplanetary Tangential Discontinuity(TD)with the bow shock and magnetosphere.Runs are performed for solar wind TDs possessing diFFerent initial half-widths.As the TD propagates through the bow shock toward the magnetopause,it is greatly narrowed by a two-step compression processes,a "shock compression" followed by a subsequent "convective compression".In cases with a relatively thin solar wind TD,3-D patchy reconnection is initiated in the transmitted TD,forming magnetosheath flux ropes.Multiple components of ion particles are present in the velocity distribution in the magnetosheath merging,accompanied by ion heating.For cases with a relatively wide initial TD,a dominant single X-line appears in the subsolar magnetosheath after the transmitted TD is narrowed.A shock analysis is performed for the detailed structure of magnetic reconnection in the magnetosheath.Rotational Discontinuity(RD)/TimeDependent Intermediate Shock(TDIS)are found to dominate the reconnection layer,which and some weak slow shocks are responsible for the ion heating and acceleration.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 NSF grant ATM-0646442 to Auburn University and the National Natural Science Foundation of China(NSFC) grant 40640420563 to Wuhan University
文摘A three-dimensional(3-D)global hybrid simulation is carried out for the generation and structure of magnetic reconnection in the magnetosheath due to interaction of an interplanetary Tangential Discontinuity(TD)with the bow shock and magnetosphere.Runs are performed for solar wind TDs possessing diFFerent initial half-widths.As the TD propagates through the bow shock toward the magnetopause,it is greatly narrowed by a two-step compression processes,a "shock compression" followed by a subsequent "convective compression".In cases with a relatively thin solar wind TD,3-D patchy reconnection is initiated in the transmitted TD,forming magnetosheath flux ropes.Multiple components of ion particles are present in the velocity distribution in the magnetosheath merging,accompanied by ion heating.For cases with a relatively wide initial TD,a dominant single X-line appears in the subsolar magnetosheath after the transmitted TD is narrowed.A shock analysis is performed for the detailed structure of magnetic reconnection in the magnetosheath.Rotational Discontinuity(RD)/TimeDependent Intermediate Shock(TDIS)are found to dominate the reconnection layer,which and some weak slow shocks are responsible for the ion heating and acceleration.
