Electron Density Cavity During Magnetic Reconnection

Magnetic reconnection is an important progress in space and laboratory plasma,which is related to kinds of blast phenomenon such as solar flare and magnetosphere substorm.As a mechanism changing magnetic energy of the field into thermal and kinetic energy of plasma,magnetic reconnection was firstly proposed by Giovanelli in the year of 1946,in order to explain the particle acceleration in solar flare.Since then,many researches in ways of simulation,observation and experiment have been taken out to study this problem.In this article,we used 2-D PIC simulation to study the evolutionary process around the area of separatrix lines during non guide field reconnection which initial state is Harris current sheet,the results are shown as follow.1.Structure of diffusion region during collisionless magnetic reconnectionThe simulation results show that,magnetize particles flow into the X point along the separatrix lines,and then flow out along the inner side of the separatrix lines after accelerated by reconnection electric field.In the period of inflow,particles can also be accelerated by the parallel electric field around the separatrix lines,which causes the decline of electron density around the area of separatrix lines(which is called electron density cavity).2.Results of simulation when changing the parametersBy changing the parameters(the ratio of electron/ion mass and light/alfven speed)of simulation,we deserved that changed ?pe/?e can change the parallel electric field around the separatrix lines,thus change the form of cavity.