X. P. Zhao, J. T. Hoeksema, and P. H. Scherrer

W. W. Hansen Experimental Physics Laboratory
Center for Space Science and Astrophysics
Stanford University, Stanford, California, 94305

ABSTRACT

The polar crown event of 1994 April 14 is one of the largest scale eruptive events observed by the Yohkoh/SXT. In addition to the formation of a large arcade of soft X ray loops and two dark 10830 ribbons, the restructuring of coronal holes bounding the arcade is also observed during the event (Alexander et al., 1994). To model the large-scale coronal structures before and after the event we must have something better than the usual monthly synoptic charts to use as input to both non-force-free helical field model (Zhao et al., 1996) and the potential field source surface model. Our improved photospheric field maps replace composite synoptic chart values in the region of interest with data from individual magnetograms observed just before or after an event. By comparing the computed magnetic fiels at different times with observed coronal structures, it may be possible to determine the causes of changes observed in the coronal structures.

Magnetograms obtained every 96 minutes from the MDI instrument on SOHO should be very useful for this kind of analysis.

Alexander, D., et al., in Proc. of the third SOHO Workshop, ESA SP-373, 187, 1994.

Zhao, X P, J T Hoeksema and P H Scherrer, in SCOSTEP STEP WG-1 Workshop, 1996.