Effects of St. Patrick's Day Geomagnetic Storm of March 2015 and of June 2015 on Low‐Equatorial D Region Ionosphere. Issue 8 (21st August 2018)

• Record Type: Journal Article
• Authors: Maurya, Ajeet K.; Venkatesham, K.; Kumar, Sushil; Singh, Rajesh; Tiwari, Prabhakar; Singh, Abhay K.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 8(2018)
• Page Start: 6836
• Page End: 6850
• Publication Date: 2018-08-21
• Subjects: VLF waves -- geomagnetic storm -- EIWG -- D region -- ionosphere -- low‐equatorial latitude; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2018JA025536
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: D region effects of the 17–19 March 2015, a St Patrick's Day super geomagnetic storm ( Dst = −223 nT), using a navigational transmitter very low frequency (VLF) signal (NWC, 19.8 kHz) recorded at a low‐latitude Indian station, Allahabad (geomag. lat., 16.45°N), have been analyzed and compared with similar strength of the 22–25 June 2015 storm ( Dst = −204 nT). During the March storm, NWC signal amplitude decreased on 17 March (main phase of the storm) and recovered on 27 March, which is 1 day after the recovery of the storm, whereas for the June storm, VLF amplitude decreased for 2 days only during its recovery phase. The decrease in the amplitude was pronounced during evening terminator for both the storms. The modeling of VLF signal anomaly on 17 March and on 25 June using Long‐Wave Propagation Capability code shows an increase in the D region reference height ( h ′) by ~2.6 km and ~2.5 km, for March and June storms, respectively. The D region electron density ( N e ) determined using storm time h ′ and sharpness factor β shows a decrease in the N e during the main phase followed by a slow recovery during the recovery phase of the March storm, whereas June 2015 storm showed a decrease in the N e only on 25 and 26 June. Morlet Wavelet analysis of the amplitude for both the storms shows a presence of strong wave‐like signatures, suggesting propagation of atmospheric gravity waves/traveling ionosphere disturbances to the low latitude D region due to the Joule heating at high latitudes. Key Points: Strong amplitude anomalies on NWC signal were observed during evening terminator time associated with the 17 March 2015 and the 25 June 2015 storms Stronger and longer duration signal amplitude anomalies occurred due to the March storm as compared to the June storm Wavelet analysis shows signature of AGWs/TIDs along the NWC Allahabad path associated with these storms