AAS 204th Meeting, June 2004
Session 46 Plasma Astrophysics of Coronae: Solar, Stellar and Accretion Disk
Topical Session, Tuesday, June 1, 2004, 2:30-4:00pm, 4:15-6:00pm, 710/712

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[46.03] Twist and Flare: The role of helical magnetic structures in the solar corona

S. Gibson (NCAR/HAO)

Solar explosive events such as coronal mass ejections (CMEs) and flares are commonly considered to be driven by the free magnetic energy stored in current carrying (twisted or sheared) coronal magnetic fields. Since it is presently not feasible to directly observe coronal magnetic fields, it is reasonable to turn to observations of flux-frozen solar plasma for evidence of such twisted magnetic field. Indeed, apparently twisted structures and rotating motions are not hard to find on the Sun. We must be cautious, however, in interpreting observations which are essentially projections of three-dimensional structures, and which highlight sub-regions of the magnetic field for specific physical reasons (for example, regions that are particularly dense or hot). In order to interpret such observations, it is essential to employ a three-dimensional, physical model that realistically simulates observable properties of the relationship between plasma and field. I will demonstrate how a model of a twisted magnetic flux rope emerging into a coronal magnetic field can be used to explain observed helical solar structures and dynamics. In particular, I will consider the structure, evolution, and relative location and orientation of S-shaped, or sigmoidal active regions and filaments. I will also discuss how the emerging flux rope can explain observed rotational and shearing motions at the solar photosphere. Finally, I will address how the emerging magnetic flux rope injects magnetic helicity into the corona, and how this drives dramatic coronal dynamics.

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