Plasma Flow Generation due to the Nonlinear Alfvén Wave Propagation around a 3D Magnetic Null Point

Abstract

Abstract The behavior of current density accumulation around the sharp gradient of magnetic field structure or a 3D magnetic null point and with the presence of finite plasma pressure is investigated. It has to be stated that in this setup, the fan plane locates at the xy plane and the spine axis aligns along the z-axis. Current density generation in presence of the plasma pressure that acts as a barrier for developing current density is less well understood. The shock-capturing Godunov-type PLUTO code is used to solve the magnetohydrodynamic set of equations in the context of wave-plasma energy transfer. It is shown that propagation of Alfvén waves in the vicinity of a 3D magnetic null point leads to current density excitations along the spine axis and also around the magnetic null point. Besides, it is pointed out the x component of current density has oscillatory behavior while the y and z components do not show this property. It is plausible that it happens because the fan plane encompasses separating unique topological regions, while the spine axis does not have this characteristic and is just a line without separate topological regions. Besides, current density generation results in plasma flow. It is found that the y component of the current density defines the x component of the plasma flow behavior, and the x component of the current density prescribes the behavior of the y component of the plasma flow.