NSF Award
0454597
A key goal of the SHINE program and of solar physics in general is to understand the initiation of coronal mass ejections (CMEs). These immense eruptions propel plasma and magnetic flux outward from the sun, and are believed to be the primary cause of major geomagnetic storms. At recent SHINE workshops, two mechanisms, "flux cancellation" and "breakout," have received prominent attention as the possible trigger for CMEs. The workshops have featured lively discussions arguing either in favor of or against these mechanisms for specific events, but no consensus has been reached concerning the plausibility of either mechanism. The central difficulty is that most of the simulations that have been put forth as examples of flux cancellation or breakout have been too idealized to address the key features observed in the specific events.<br/><br/>In this proposal, the proposers describe a three-year program to investigate the flux cancellation and breakout models of CMEs. The overall goal is to determine whether either of these models can produce eruptions for parameters similar to real events. Specifically, the PI and his team will: <br/><br/>* Develop MHD models of the corona for the time of two well studied events: the May 12, 1997 CME event and the July 14, 2000 "Bastille Day" event;<br/>* Investigate the magnetic field topology of the configurations when solar wind is included, especially changes to the location of separatrix surfaces (which are crucial for the breakout model);<br/>* Study whether flux changes leading up to the event with the SOHO MDI instrument are sufficient to produce eruptions;<br/>* Diagnose the role of the competing effects of reconnection through separatrix surfaces (breakout) versus reconnection at the photosphere (flux cancellation) in producing eruptions; and<br/>* Assess each mechanism's feasibility as the trigger for these events.
