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Session 1 - Chromosphere, Corona, Flares.
Display session, Friday, June 27
Ballroom B, Chair: Charles Kankelborg
It has long been thought that solar magnetic structures such as arcades and flux ropes can erupt if the photospheric footpoints of the magnetic field lines are slowly sheared. The possible mechanisms of eruption include catastrophic loss of equilibrium and some large-scale instabilities such as the MHD kink instability. In this ``storage-release'' scenario, the shearing motion increases the twist in the coronal field, which is equivalent to a quasi-static increase in the energy associated with the horizontal component of the field of an arcade or the poloidal field of a flux rope. Alternatively, it has been shown recently  that an equilibrium flux rope under coronal conditions and comparable in size to quiescent prominences can erupt if the poloidal flux is increased on the timescale of eruption. The resulting dynamical properties are consistent with those of CMEs/eruptive prominences, and the computed model structure in the heliosphere closely resembles observed interplanetary magnetic clouds. We explore potentially observable signatures of this alternative scenario in which the initial structure (e.g., a flux rope) is driven by newly emergent magnetic flux. We increase the poloidal flux both quasi-statically and on the timescale of eruption. We compare the different dynamical behaviors in terms of physical observables such as the acceleration/speed of eruption, variation in the magnetic field of the flux rope, and the resulting structures at 1 AU, which can be observed by in situ measurements. The initial equilibrium flux rope and the ``erupting'' flux rope are both found to be stable to the kink mode. The physical processes in the driven versus storage-release scenarios are discussed, and possible observational discriminators are suggested.
1. Chen, J., JGR, vol. 101, 27499, 1996
Program listing for Friday