Simulation of a breakout coronal mass ejection in the solar wind

The initiation and evolution of coronal mass ejections (CMEs) is studied by means of the breakout model embedded in a 2.5D axisymmetric solar wind in the framework of numerical magnetohydrodynamics (MHD). The initial, steady equilibrium contains a pre-eruptive region consisting of three arcades with alternating magnetic flux polarity and with correspondingly three neutral lines on the photosphere. The magnetic tension of the overlying closed magnetic field of the helmet streamer keeps this structure in place. The most crucial part of the initial breakout topology is the existence of an X-point on the leading edge of the central arcade. By shearing part of this arcade, the reconnection with the overlying streamer field is turned on. The initial phase of the erupting arcade then closely follows the original breakout scenario. The breakout reconnection opens the overlying field in an energetically efficient way leading to an ever faster eruption. However, from a certain moment two new reconnections set in on the sides of the erupting central arcade and the breakout reconnection stops. The consequence of this change in reconnection location is twofold: (1) the lack of breakout reconnection so that the breakout plasmoid fails to become a fast CME; and (2) an eventual disconnection of the large helmet top resulting in a slow CME.