Other
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...210.2918t&link_type=abstract
American Astronomical Society Meeting 210, #29.18; Bulletin of the American Astronomical Society, Vol. 39, p.140
Other
Scientific paper
A simple model of the coronal magnetic field prior to the CME eruption on May 12 1997 is developed. First, this field is constructed by superimposing a large-scale background field and a localized bipolar field to model the active region (AR) in the potential approximation. The background field is determined from the observed photospheric normal field averaged over the longitude of the Sun. The AR field is modeled by a subphotospheric dipole whose parameters are optimized to fit the magnetic field obtained from an MDI magnetogram. Second, this potential configuration is quasi-statically sheared by photospheric vortex motions applied to two flux concentrations of the AR. Third, the resulting force-free field is then evolved by canceling the photospheric flux with the help of a flow converging to the neutral line of the AR. To understand the structure of the modeled configuration, we use a field line mapping technique generalized to spherical geometry. It is demonstrated that the initial configuration contains a hyperbolic flux tube (HFT) consisting of two intersecting quasi-separatrix layers. This HFT provides a partition of the closed magnetic flux between the AR and global solar magnetic field. Such a partition is approximate since the entire flux distribution is perfectly continuous. The vortex motions applied to the AR interlock the coronal field lines to form additionally two new HFTs pinched into thin current layers (CLs). These CLs carry the return current shielding the twisted field of the AR from a nearly potential background field. Reconnection in these CLs helps redistribute the flux in the configuration during the cancellation phase. At this phase, a magnetic flux rope is formed together with a bald patch separatrix surface wrapping around the rope. Other important implications of the identified structural features of the modeled configuration are also discussed.
Linker Jon A.
Lionello Roberto
Mikic Zoran
Titov Viacheslav
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