A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. I. Unusual History of an Eruptive Filament

摘要

This is the first of four companion papers, which analyze a complex eruptiveevent of 18 November 2003 in AR 10501 and the causes of the largest Solar Cycle23 geomagnetic storm on 20 November 2003. Analysis of a complete data set, notconsidered before, reveals a chain of eruptions to which hard X-ray andmicrowave bursts responded. A filament in AR 10501 was not a passive part of alarger flux rope, as usually considered. The filament erupted and gave originto a CME. The chain of events was as follows: i) an eruption at 07:29accompanied by a not reported M1.2 class flare associated with the onset of afirst southeastern CME1, which is not responsible for the superstorm; ii) aconfined eruption at 07:41 (M3.2 flare) that destabilized the filament; iii)the filament acceleration (07:56); iv) the bifurcation of the eruptive filamentthat transformed into a large cloud; v) an M3.9 flare in AR 10501 associated tothis transformation. The transformation of the filament could be due to itsinteraction with the magnetic field in the neighborhood of a null point,located at a height of about 100 Mm above the complex formed by ARs 10501,10503, and their environment. The CORONAS-F/SPIRIT telescope observed the cloudin 304 A as a large Y-shaped darkening, which moved from the bifurcation regionto the limb. The masses and kinematics of the cloud and the filament weresimilar. Remnants of the filament were not observed in the second southwesternCME2, previously regarded as a source of the 20 November superstorm. Thesefacts do not support a simple scenario, in which the interplanetary magneticcloud is considered as a flux rope formed from a structure initially associatedwith the pre-eruption filament in AR 10501. Observations suggest a possibleadditional eruption above the bifurcation region close to solar disk centerbetween 08:07 and 08:17 that could be the source of the superstorm.