The CME-Flare Current Sheet Predicted by the Catastrophe Model of the Solar Eruption and Detected in CME-Flare Events

Abstract:

It was predicted by the catastrophe model of the solar eruption that a long current sheet should develop in the major eruption as a result of the competition between disrupting of the coronal magnetic structure and magnetic reconnection taking place in the current sheet itself separating magnetic fields of opposite polarity. The length of the current sheet and the dynamics of the ejecta are dominated by both the rate of magnetic reconnection and the background magnetic field. Formation and development of the long current sheet were soon confirmed by the observation soon after the model was built up. In addition, the current sheet connecting the CME to the associated flare was found to be much thicker than expected by the traditional theory of magnetic diffusion. Works in both theory and observations to help understand the physics behind the unexpected large scale of the sheet have been performed for many years, but the question is still open. Recent numerical experiments tend to suggest that it is the turbulence due to the plasma instability inside the current sheet that accounts for the thick current sheet in which magnetic reconnection undergoes at a reasonably fast rate to guarantee the fast energy conversion required for the major eruption. In this review, we first introduce how the catastrophe model for solar eruptions predicted the formation and development of the long current sheet and how the observations were used to recognize the current sheet at the place where the current sheet is presumably located. Then, we discuss the studies of various features of the current sheet performed in the last decade, including investigations of its geometric scale and internal fine structures, as well as the possible physics behind observations.