Drive Mechanisms of Erupting Solar Magnetic Flux Ropes

The dynamics of magnetic flux ropes near the Sun and in interplanetary space are studied using a magnetohydrodynamic model of erupting magnetic flux ropes. In this model, the magnetic structure of a coronal mass ejection (CME) corresponds to a flux rope with footpoints that remain anchored below the photosphere. The model flux rope eruption can be driven by a rapid increase in poloidal flux (flux injection), a quasi-static increase in poloidal flux (photospheric footpoint twisting), a rapid release of stored magnetic energy (magnetic energy release), or a rapid increase in the amount of hot plasma within the flux rope (hot plasma injection). Model results are compared with Large-Angle Spectrometric Coronagraph data (from the CME of 1997 April 13) and with interplanetary magnetic cloud data over the range 0.4-5 AU. Of these mechanisms, only flux injection and magnetic energy release reproduce key features of the data both near the Sun and in the interplanetary medium and only flux injection obtains a detailed match to the near-Sun dynamics.