On the evolution of a magnetic flux rope: Two‐dimensional MHD simulation results

Abstract

AbstractWe use the time‐dependent, two‐dimensional (2‐D), ideal MHD equations to simulate and investigate the evolution of magnetic field and plasma profiles of the typical (T) and crater (C) magnetic flux ropes (FRs). The T‐FR has a magnetic pressure peak at the center of the flux rope, while the C‐FR has a local dip instead. The simulation starts with a 2‐D magnetic flux rope in magnetohydrostatic equilibrium, where pressure gradient forces are balanced by Lorentz forces. The magnetic field and plasma pressure profiles for the initial flux rope are derived from the analytical solutions by Zhang et al. (2010). The initial flux rope starts to evolve when the force balance is broken by imposing pressure or magnetic field perturbations onto the equilibrium system. The pressure perturbations are produced by increasing/decreasing the internal plasma pressure of the flux rope, while the magnetic field perturbations are produced by increasing/decreasing the transverse magnetic fields across the flux rope. We conclude that a T‐FR can be evolved into a C‐FR and vice versa, if the perturbation strength is sufficient, and that the plasma pressure and density in the new equilibrium state could be either increased or decreased for the evolution of C‐FR to T‐FR and also for the evolution of T‐FR to C‐FR.