Hall MHD Simulation Study Of Asymmetric Magnetic Reconnection With External Shear Flow

Magnetic reconnection has been widely considered to play a key role in some phenomena in space and laboratory plasmas where instability bursts.However,the reconnection process under the influence of magnetic field or density asymmetry,shear flow and guide field has not been well understood.Due to the practical difficulties in space observation and the limitations in theoretical analysis,numerical simulation is the most common method to understand the reconnection process.In this paper,asymmetric magnetic reconnection process with external shear flow is studied basing on Hall MHD numerical simulation method,and the following results are obtained.1.In the asymmetric reconnection pattern with external shear flow,we find X point moves in X direction.At the same time,a negative reconnection electric field is formed in the left magnetic flux accumulation area of X-point,while a positive reconnection electric field is formed in the right area.Reconnection electric field of bipolar structure is mainly contributed by (?) term.We further explore the energy conversion phenomenon in the reconnection process,including systematical analysis of the mutual transformation within magnetic energy,thermal energy and kinetic energy.In the case that the total energy in the plane is basically balanced,energy transfer phenomenon of the total energy appears in the flux accumulation area.Loss of the total energy in the right magnetic flux accumulation area of the X-point is transferred to the left area.Transfer of the total energy outside of the magnetic island mainly comes from the change of magnetic energy,while which inside the magnetic island mainly comes from the change of internal energy inside of the magnetic island.2.In the asymmetric reconnection pattern of magnetic field with external shear flow,as well as a high plasmas beta,slow shock can also be formed.3.In the symmetric pattern with sub-Alfvenic shear flow,when the current sheet of half width is larger than that of shear flow,K-H instability is easily induced by shear flow in the current sheet,which causes turbulence resulting in the increase of magnetic energy.When d_i=0.2,under the strong Hall effect,the magnetic energy further increases due to the magnetic island merging,which forms the second peak.