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

The impact of the St. Patrick's Day storm (17 March 2015) on the major equatorial electrodynamical process viz., the equatorial ionization anomaly (EIA) has been assessed using 2-D (5 degrees latitude x 5 degrees longitude) total electron content (TEC) maps generated from the ground-based 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 2-D TEC maps, which have a large latitudinal (5 degrees S-45 degrees N) and longitudinal (55-110 degrees 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 structure of the EIA. It has been shown unambiguously that even a separation of similar to 10 degrees-15 degrees 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.