Ionospheric response to the 2015 St. Patrick's Day storm: A global multi-instrumental overview

• Published in: Journal of geophysical research. Space physics 2015-10, Vol.120 (10), p.9023-9037
• Main Authors: Astafyeva, Elvira, Zakharenkova, Irina, Förster, Matthias
• Format: Article
• Language: English
• Subjects: Asymmetry; Earth Sciences; Geodetics; Geomagnetic field; geomagnetic storm; Geophysics; hemispheric asymmetry; Inverse; Ionosphere; Ionospheric storms; Ionospherics; Latitude; Magnetic fields; negative storm; Physics; positive storm; Sciences of the Universe; Signatures; Solar cycle; Solar cycles; Space Physics; Storms; Swarm mission
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2015JA021629

We present the first multi‐instrumental results on the ionospheric response to the geomagnetic storm of 17–18 March 2015 (the St. Patrick's Day storm) that was up to now the strongest in the 24th solar cycle (minimum SYM‐H value of −233 nT). The storm caused complex effects around the globe. The most dramatic positive ionospheric storm occurred at low latitudes in the morning (~100–150% enhancement) and postsunset (~80–100% enhancement) sectors. These significant vertical total electron content increases were observed in different local time sectors and at different universal time, but around the same area of the Eastern Pacific region, which indicates a regional impact of storm drivers. Our analysis revealed that this particular region was most concerned by the increase in the thermospheric O/N2 ratio. At midlatitudes, we observe inverse hemispheric asymmetries that occurred, despite the equinoctial period, in different longitudinal regions. In the European‐African sector, positive storm signatures were observed in the Northern Hemisphere (NH), whereas in the American sector, a large positive storm occurred in the Southern Hemisphere, while the NH experienced a negative storm. The observed asymmetries can be partly explained by the thermospheric composition changes and partly by the hemispherically different nondipolar portions of the geomagnetic field as well as by the IMF By component variations. At high latitudes, negative ionospheric storm effects were recorded in all longitudinal regions, especially the NH of the Asian sector was concerned. The negative storm phase developed globally on 18 March at the beginning of the recovery phase. Key Points Multi‐instrumental analysis of the ionospheric storm of 17–18 March 2015 Inverse hemispheric asymmetries in VTEC in the American and European‐African longitudinal sectors Extreme topside TEC enhancement over the Eastern Pacific region was observed at different UT and LT