34th Solar Physics Division Meeting, June 2003
Session 5 Coronal Mass Ejections I
Poster, Monday, June 16, 2003, 3:30-5:00pm, Mezzanine

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[5.17] The Energetics of Breakout Coronal Mass Ejections

C. R. DeVore, S. K. Antiochos (NRL)

A key obstacle to understanding fast coronal mass ejections lies in slowly accumulating sufficient magnetic energy to power an explosive eruption of the structure, rather than a gradual expansion, and then rapidly releasing the stored energy when a threshold is crossed and the event is triggered. In the breakout model, a low-lying stressed field is restrained by an overlying coronal field containing an embedded null. The abrupt transition to explosive behavior occurs when reconnection at the null lowers the energy required to open the remnant restraining flux below the free energy stored in the stressed field.

We investigate the energetics of opening the coronal magnetic field under two possible extremes of evolution: (1) complete reconnection at the null produces a ‘maximally closed’ final state, whose free energy is the lower bound for opening the structure; (2) zero reconnection at the null produces a ‘maximally open’ final state, whose free energy is an upper bound. We calculate the energies of these states for coronal fields that are potential everywhere except at discrete current sheets, where the magnetic stresses are continuous and the field is force-free. Varying the relative amounts of flux in the inner arcade and the overlying field shifts the location of the potential null. In axisymmetric spherical geometries, the free energies of the ‘maximally closed’ states can be less than 2.5% of the energy of the initial configuration, and as small as 125% of the initial energy of the inner arcade, with the null positioned at 1.4 and 1.6 Rs, respectively. These findings change little as the surface distributions of arcade and overlying flux are increasingly concentrated, and all energy-minimizing states have a net amount of open overlying flux. Results for fully three-dimensional, nonaxisymmetric breakout configurations will be presented.

This research was supported in part by NASA and ONR.


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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.