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J. Lin, A. A. van Ballegooijen (Harvard-Smithsonian Center for Astrophysics)
We investigate a coronal magnetic configuration including a semi-circular flux rope with two ends anchored in the photosphere. The background field is produced by two source regions on the photosphere. We study the evolution of this configuration in response to the gradual change in the background field, which is modeled by varying either the strength of the source or the length scale of the source region. Our results indicate that the evolution due to the change in source strength shows the likelihood of catastrophic loss of equilibrium, and that the evolution due to the change in the length scale is smooth and does not manifest any intention to lose equilibrium. In the former case, the current sheet starts developing fairly early, it forms even before the evolution reaches the maximum current state. We notice that the effect of the curvature of flux rope on the evolution of the system is significant, such that the equilibrium curve does not form a cusp-catastrophic structure but a simple fold-catastrophic structure even if the evolution is ideal MHD and a current sheet attached to the boundary surface develops. The curvature strengthens the magnetic compression between the flux rope and the photosphere, and makes the loss of equilibrium easier. But the question of how the system behaves after loss of equilibrium is still open since the flux rope may not be able to remain semi-circular at the stage of fast evolution.
The author(s) of this abstract have provided an email address for comments about the abstract: jlin@cfa.harvard.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.