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We study the solar sources of an intense geomagnetic storm of solar cycle 23that occurred on 20 November 2003, based on ground- and space-basedmultiwavelength observations. The coronal mass ejections (CMEs) responsible forthe above geomagnetic storm originated from the super-active region NOAA 10501.We investigate the H-alpha observations of the flare events made with a 15 cmsolar tower telescope at ARIES, Nainital, India. The propagationcharacteristics of the CMEs have been derived from the three-dimensional imagesof the solar wind (i.e., density and speed) obtained from the interplanetaryscintillation data, supplemented with other ground- and space-basedmeasurements. The TRACE, SXI and H-alpha observations revealed two successiveejections (of speeds ~350 and ~100 km/s), originating from the same filamentchannel, which were associated with two high speed CMEs (~1223 and ~1660 km/s,respectively). These two ejections generated propagating fast shock waves(i.e., fast drifting type II radio bursts) in the corona. The interaction ofthese CMEs along the Sun-Earth line has led to the severity of the storm.According to our investigation, the interplanetary medium consisted of twomerging magnetic clouds (MCs) that preserved their identity during theirpropagation. These magnetic clouds made the interplanetary magnetic field (IMF)southward for a long time, which reconnected with the geomagnetic field,resulting the super-storm (Dst_peak=-472 nT) on the Earth.

Multiwavelength Study on Solar and Interplanetary Origins of the Strongest Geomagnetic Storm of Solar Cycle 23