34th Solar Physics Division Meeting, June 2003
Session 16 Flares and Microflares II
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[16.23] The Solar Magnetic Field and Corona During Geomagnetic Superstorms

J.G. Luhmann, Yan Li (SSL, University of California, Berkeley), C.N. Arge (CIRES, U. of Colorado and NOAA-SEC), J. Boyden, R. Ulrich (Department of Physics and Astronomy, UCLA)

Geomagnetic superstorms were characterized by Bell et al. (JGR v102, p.14,189, 1997) by the extreme response of the magnetosphere to the causative interplanetary disturbances. Many superstorms involve large negative Dst index values, which are known to occur when an interplanetary coronal mass ejection, or ICME, has particularly large and long-lived southward interplanetary fields together with enhanced plasma densities and/or velocities. While several authors have analyzed the upstream in-situ measurements accompanying such periods, the condition of the solar magnetic field and corona at the time has never been closely examined. We investigate the character of the prevailing photospheric and coronal field conditions, and related solar wind stream context, using the archive of Mt. Wilson Observatory magnetograph observations and models based on those data. In particular, we ask the question of whether anything special in the combination of solar and coronal field or solar wind structure would have distinguished this period ahead of time, before the storm occurred. The results bear on the predictability of geomagnetic superstorms.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.