Magnetic reconnection underlies the physical mechanism of explosive phenomena in the solar atmosphere and plan-etary magnetospheres,where plasma is usually collisionless.In the standard model of collisionless magnetic reconnection,the diffusion region consists of two substructures:an electron diffusion region is embedded in an ion diffusion region,in which their scales are based on the electron and ion inertial lengths.In the ion diffusion region,ions are unfrozen in the magnetic fields while electrons are magnetized.The resulted Hall effect from the different motions between ions and electrons leads to the production of the in-plane currents,and then generates the quadrupolar structure of out-of-plane mag-netic field.In the electron diffusion region,even electrons become unfrozen in the magnetic fields,and the reconnection electric field is contributed by the off-diagonal electron pressure terms in the generalized Ohm's law.The reconnection rate is insensitive to the specific mechanism to break the frozen-in condition,and is on the order of 0.1.In recent years,the launching of Cluster,THEMIS,MMS,and other spacecraft has provided us opportunities to study collisionless magnetic reconnection in the Earth's magnetosphere,and to verify and extend more insights on the standard model of collisionless magnetic reconnection.In this paper,we will review what we have learned beyond the standard model with the help of observations from these spacecraft as well as kinetic simulations.

Quanming Lu;Huishan Fu;Rongsheng Wang;San Lu

CAS Key Laboratory of Geospace Environment,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;CAS Center for Excellence in Comparative Planetology,Hefei 230026,China;School of Space and Environment,Beihang University,Beijing 100191,China;Key Laboratory of Space Environment Monitoring and Information Processing,Ministry of Industry and Information Technology,Beijing 100191,China

中国物理B（英文版）

[1]Quanming Lu;Huishan Fu;Rongsheng Wang;San Lu-.Collisionless magnetic reconnection in the magnetosphere)[J].中国物理B（英文版）,2022(08):110-125

Collisionless,etary,magnetospheres,quadrupolar

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