The impact of the 17 March 2015 St. Patrick's Day storm on the evolutionary pattern of equatorial ionization anomaly over the Indian longitudes using high-resolution spatiotemporal TEC maps: New insights

Abstract

The impact of the St. Patrick's Day storm (17 March 2015) on the major equatorial electro-dynamical process viz., the Equatorial Ionization Anomaly (EIA) has been assessed using 2D (5 ° lat. x 5 ° long.) total electron content (TEC) maps generated from the ground based SBAS (Satellite Based Augmentation System) enabled receiver data. The various aspects of EIA specifically the i) evolution/devolution, ii) longitudinal structure, and iii) its variability during different phases of a geomagnetic storm, have been brought out. These 2D TEC maps, which have a large latitudinal (5 S-45° N) and longitudinal (55-110° E) coverage, show the complete reversal in the longitudinal structure/pattern of EIA during the recovery phase of the storm as compared to the quiet day. These results have been explained in the light of the combined effects of the storm associated processes such as i) the penetration electric fields of magnetosphere origin, ii) storm-induced thermospheric winds, and, iii) activation of the consequent disturbance dynamo effectively distorting the longitudinal wave number 4 (WN4) structure of the EIA. It has been shown unambiguously that even a separation of ~10°-15° longitude could experience significantly different forcings. The relevance and the far reaching consequences of the study in the light of the current trends and requirements for reliable satellite based navigation are highlighted.