Features of storm‐induced ionospheric irregularities from ground‐based and spaceborne GPS observations during the 2015 St. Patrick's Day storm

During geomagnetic disturbances, the solo or combined effect of prompt penetration electric fields (PPEFs) and disturbance dynamo electric fields (DDEFs) alters radically regular pattern of equatorial plasma bubbles (EPBs) occurrence. The severe 17-18 March 2015 storm is an excellent event to trace how the storm reshapes EPB generation at all longitudinal sectors. We present results of a comprehensive analysis of storm-induced EPBs based on combination of in situ and remote sensing techniques including 6,100+ ground-based GNSS stations, in situ plasma observations onboard Swarm, Communications/Navigation Outage Forecasting System (C/NOFS), and Defense Meteorological Satellite Program (DMSP) satellites, COSMIC Global Positioning System (GPS) scintillations, and up-looking GPS observations onboard Swarm. During the main storm phase, the PPEF-induced postsunset EPBs occurred over Australian and Indian sectors. Both events were characterized by plasma bite-out near the magnetic equator and strong plasma depletions at low/midlatitudes that caused strong GPS signal scintillations in the topside ionosphere. Long-lasting DDEFs led to suppression of postsunset EPBs and promoted postmidnight/predawn EPBs in African/American/Pacific sectors. The first DDEF-induced EPBs were registered similar to 6 hr after storm commencement in the midnight-dawn sector of the Pacific Ocean during short-term recovery period (09-12 UT on 17 March). In a succession of postsunset EPB suppression under DDEFs, an exclusive event with a single postsunset EPB development was registered in South America at the recovery phase beginning (23-24 UT) due to an unknown PPEF-like source. During recovery phase, several large-scale EPBs with an estimated inter-bubble distance of similar to 1,000 km occurred almost simultaneously in the predawn sector in South America and was well sustained till similar to 07-08 LT in the morning.