Cosmic Noise Absorption Characteristics during the Impulse-Induced Supersubstorm of 21st January 2005

Abstract

The impulse-induced super substorm of 21st January 2005 has been reported by Hajra and Tsurutani (2018) and they have discussed the abnormal morphology of the auroral dynamics mainly examining the auroral images and currents. This event is revisited here with additional datasets of global Cosmic Noise Absorption (CNA) by Riometers, auroral images by a space-based Imager, plasma flux data from geostationary satellites and magnetic field measurements of ground stations covering almost all latitudinal and local time sectors. We have observed some peculiar characteristics of this event: (1) No southward component of IMF Bz prior to the substorm onset. (2) Westward electrojet current peaks in the dawn sector, and not in the midnight sector, during the substorm interval. (3) Presence of dayside shock-auroras: The electron & proton auroras are stronger in the pre and post-midnight sectors and strongest on the dayside. (4) The time of CNA onset and substorm onset coincide in the narrow belt of magnetic latitude near 65°. The time delay between these two increases away from this belt on both-poleward and equatorward latitudes. The delay is small (~ 2 minutes) on the dayside and significant (~11 minutes) on the night side. (5) The percentage of CNA is found to vary with MLT as well as with latitudes. CNA absorption is lowest on the dayside (~20%) whereas near dawn and dusk the percentage of CNA is nearly equal (~40-50%). (6) Considering the model proposed by Sorathia et al. (2019) we can say that the dawn-dusk symmetry observed in the CNA indicates the entry of particles from the flanks facilitated by Kelvin-Helmholtz instability.