Hall MHD Simulation Of 3D Structures In Magnetic Reconnection

In space and celestial bodies,as well as laboratory plasma,there are many "explosive" large-scale energy conversion phenomena,such as solar flares,coronal heating,magnetic storms and substorms of the earth,and sawtooth oscillations in tokamak plasma,discharge rupture and other physical phenomena.At present,it is generally believed that these large-scale transient phenomena are closely related to the process of magnetic reconnection.Magnetic reconnection is one of the basic physical processes of the interaction between plasma and magnetic field.Since the concept of magnetic reconnection was proposed in 1946,scientists studying magnetic reconnection have been working to establish a theory of rapid magnetic reconnection that can be practical.The results of space observations and ground experiments confirm that Hall magnetic reconnection plays a leading role in the rapid magnetic reconnection process.However,the topological structure and physical process of magnetic reconnection are essentially three-dimensional.Although the current research results(mainly the Hall effect mechanism and sub-Alfvénic rate of fast magnetic reconnection)have been able to characterize the magnetic reconnection process well under the two-dimensional approximation,for the microscopic plasma in the fast magnetic reconnection In the dynamic process,the three-dimensional effect(including asymmetry)of the magnetic field structure is very significant.Therefore,this article mainly starts from the three-dimensional magnetic reconnection,and conducts simulation research on the evolution law of the physical quantities of the three-dimensional magnetic reconnection and the three-dimensional structure of the magnetic field lines.In this paper,two-dimensional and three-dimensional Hall magnetohydrodynamic models are used to describe the evolution process of magnetic reconnection,using continuity equation,momentum equation,energy conservation equation and Maxwell's equation,and the evolution law of each physical quantity in the process of magnetic reconnection and magnetic reconnection are analyzed.The evolution curve of island width with time,the evolution curve of current with time,and the topological structure of magnetic field lines of three-dimensional magnetic reconnection are analyzed.After analysis,we get that: Compared with the two-dimensional model,it takes longer for the magnetic reconnection to occur under the three-dimensional model,and the Hall effect can effectively accelerate the rate of magnetic reconnection.At the same time,due to the Hall effect,the magnetic field perpendicular to the direction of the reconnection plane(guide field)presents a typical quadrupole magnetic field structure.The magnetic field directed in the direction of the field causes the three-dimensional magnetic lines of force to bend in the direction of the directed field.Compared with the symmetric current sheet,the rate of magnetic reconnection in the asymmetric current sheet structure is reduced,and under the condition of constant pressure,the density asymmetry has a more obvious effect than the temperature asymmetry in reducing the reconnection rate,but both In this case,the three-dimensional magnetic field line structure of asymmetric magnetic reconnection is basically the same.In addition,the externally directed magnetic field has a significant effect on the magnetic field line structure of the three-dimensional magnetic reconnection.In the end,the magnetic field topology of the three-dimensional magnetic reconnection is determined by the combined action of the external guiding magnetic field,the Hall effect,and the asymmetry of the system.And when the Hall effect,the external guiding magnetic field,and the asymmetry exist at the same time,the influence on the three-dimensional structure of the magnetic lines of force is successively weakened.