Title:  The Magnetic Origins of Coronal Mass Ejections
Author(s):  S. Antiochos   Main Session Speaker

ABSTRACT
The most spectacular and most energetic manifestations of solar activity are the giant disruptions of the Sun's magnetic field that give rise to coronal mass ejections (CME)/ eruptive flares. These events are also the main drivers of geoeffective space weather, producing disturbances ranging from intense particle storms to electric power disruptions.  CMEs/eruptive flares are also, perhaps, the most interesting form of solar activity from the viewpoint of basic MHD physics and present a great challenge to theory. Recent observations by the SOHO and TRACE missions of CMEs/flares and their associated prominence eruptions have given us new insights into the physical mechanism for CME/eruptive flare initiation. We will first review some of the latest observations and theories. Then, we will describe a recently developed model, "magnetic breakout", which appears to explain many of the important features of CME/eruptive flares.  The basic idea underlying breakout is that the interaction of neighbouring flux systems in the Sun's corona leads to a positive feedback between magnetic reconnection and outward expansion of the coronal magnetic field, and thereby, an explosive energy release. Both 2.5D and 3D numerical simulations of breakout will be presented. The model describes a general mechanism for explosive eruptions, which should be applicable to many astrophysical plasmas.