Quiet time variability of the GPS TEC and EEJ strength over Indian region associated with major sudden stratospheric warming events during 2005/2006

Abstract

This paper describes the quiet time variabilities of the ionospheric total electron content (TEC) derived from the signals from Global Positioning Satellite System (GPS) recorded at several stations in India along with simultaneous observations of equatorial electrojet (EEJ) strength obtained from geomagnetic field variations during January–March 2006 when sudden stratospheric warming (SSW) events occurred. Analysis of the observations presented here confirms that strong correlation exists among the variabilities in EEJ strength and GPS TEC observations. Investigations suggest that there exist large-scale wave like structures with periodicity of quasi 16-day wave in the TEC observations near the equatorial ionization anomaly (EIA) crest quite similar to that of EEJ strength. Our observations also indicate the existence of morning enhancement and evening reduction of TEC and EEJ strength and vice versa during SSW events similar to that reported elsewhere. Using these observations, it is suggested that the quiet time variabilities seen in the GPS TEC over EIA could be caused due to the nonlinear interaction of upward propagating planetary waves (PWs) with atmospheric tides. Presence of similar periods in the EEJ strength and TEC observations near the EIA crest region, supports the view that the large-scale wave like structures seen in TEC near the EIA crest are associated with PWs that are modifying the primary eastward electric field in the equatorial E region and hence the EEJ strength through non linear interactions with atmospheric tides.