Three‐dimensional MHD simulation of a flux rope driven CME

Abstract

We present a three‐dimensional (3‐D) numerical ideal magnetohydrodynamics (MHD) model, describing the time‐dependent expulsion of plasma and magnetic flux from the solar corona that resembles a coronal mass ejection (CME). We begin by developing a global steady‐state model of the corona and solar wind that gives a reasonable description of the solar wind conditions near solar minimum. The model magnetic field possesses high‐latitude coronal holes and closed field lines at low latitudes in the form of a helmet streamer belt with a current sheet at the solar equator. We further reproduce the fast and slow speed solar wind at high and low latitudes, respectively. Within this steady‐state heliospheric model, conditions for a CME are created by superimposing the magnetic field and plasma density of the 3‐D Gibson‐Low flux rope inside the coronal streamer belt. The CME is launched by initial force imbalance within the flux rope resulting in its rapid acceleration to a speed of over 1000 km/s and then decelerates, asymptotically approaching a final speed near 600 km/s. The CME is characterized by the bulk expulsion of ∼1016 g of plasma from the corona with a maximum of ∼5 × 1031 ergs of kinetic energy. This energy is derived from the free magnetic energy associated with the cross‐field currents, which is released as the flux rope expands. The dynamics of the CME are followed as it interacts with the bimodal solar wind. We also present synthetic white‐light coronagraph images of the model CME, which show a two‐part structure that can be compared with coronagraph observations of CMEs.