Solar Physics Division Meeting 2000, June 19-22
Session 14. Flares and Transients
Oral, Chair: P. L. Bornmann, Thursday, June 22, 2000, 11:00am-12:00noon, 1:30-2:30pm, Forum

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[14.01] Formation and Stability of Helical Prominence Magnetic Fields

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

We have numerically simulated the evolution of initially bipolar magnetic fields, subjected to shear motions concentrated near and directed parallel to the polarity inversion line at the photosphere. The simulations yield three principal results: (1) Footpoint displacements comparable to the bipole's depth produce a dipped geometry in the sheared core flux, capable of supporting condensed prominence material against gravity. This confirms and extends the previous results of force-free field models. (2) For much larger displacements, a new mechanism for helical field formation ensues. A two-step reconnection process acts first to reconnect the sheared core flux with flux from the overlying arcade, and then to reconnect pairs of the newly formed field lines with each other. The resultant helical field threads and envelops the body of the prominence. (3) Even for very large displacements, the dipped, helical structure finds a stable equilibrium. Despite the substantial amounts of reconnection and twist in the field, it shows no sign of eruption due to kink instability or tether-cutting. The results suggest that even helical prominence configurations in simple, bipolar topologies are immune to eruption, and do not lead to coronal mass ejections; a multipolar, break-out topology may be essential.

This research was supported by NASA and ONR.

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