Numerical simulations of the initiation and the IP evolution of coronal mass ejections

Stefaan Poedts

CPA/K.U.Leuven (Belgium)

Coronal Mass Ejections (CMEs) belong to the most violent and fascinating events in the solar system. These events involve large-scale changes in the coronal structure and significant disturbances in the solar wind. Especially the massive, fast CMEs are interesting to study as these events cause shocks that propagate through the interplanetary (IP) space. In these IP shock waves energetic particles continuously accelerate giving rise to gradual solar energetic particle events (SEPs). As a result, CMEs and the CME generated shock waves play a key role in the so-called space weather. Better mathematical models of the solar corona and of CME initiation events and IP CME evolution are required. We present recent results from numerical simulations of the initiation and IP evolution of CMEs in the framework of ideal magnetohydrodynamics (MHD). As a first step, the magnetic field in the lower corona and the background solar wind are reconstructed. Both simple, axi-symmetric (2.5D) solar wind models for the quiet sun as more complicated 3D solar wind models taking into account the actual coronal field through magnetogram data are reconstructed. In a second step, fast CME events are mimicked by superposing high-density plasma blobs on the background wind and launching them in a given direction at a certain speed. In this way, the evolution of the CME can be modeled and its effects on the coronal field and background solar wind studied. In addition, more realistic CME onset models have been developed to investigate the possible role of magnetic foot point shearing and magnetic flux emergence/disappearance as triggering mechanisms of the instability. Parameter studies of such onset models reveal the importance of the background wind model that is used and of the initiation parameters, such as the amount and the rate of the magnetic flux emergence or the region and the amount of foot point shearing.