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Equatorial ionospheric TEC and scintillations under the space weather events of 4–9 September 2017: M-class solar flares and a G4 geomagnetic storm

Kumar, Sushil and Kumar, Sarvesh (2020) Equatorial ionospheric TEC and scintillations under the space weather events of 4–9 September 2017: M-class solar flares and a G4 geomagnetic storm. Journal of Atmospheric and Solar-Terrestrial Physics, 209 . p. 105421. ISSN 1364-6826

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Abstract

The observations of vertical total electron content (VTEC) and L1 and L2 band ionospheric scintillations at an equatorial station, Tarawa (Geomag. Coordinates, 2.68°S, 114.26°W), Kiribati, under a complex severe space weather event of 4–9 September 2017, are presented. The VTEC increased significantly by 1.03 and 1.31 TEC units under M5.5 class flare at 20:28 UT on 04 September and M4.2 flare at 01:03 UT on 05 September, respectively, under the quiet geomagnetic conditions. A positive ionospheric storm with a maximum percentage change in VTEC (ΔVTEC%) of 16.7% followed by a negative ionospheric storm with ΔVTEC% of 32.8% occurred during the first main phase (Dst=- 142 nT) and recovery of 7–8 September storm. This positive ionospheric effect occurred due to the combined effects of prompt penetrating electric fields (PPEFs) and suddenly enhanced EUV and X-radiations associated with M class (3.9, 1.3 &1.2) flares whereas negative ionospheric effect could be accounted for the disturbance dynamo electric fields (DDEFs) and change in the storm-time O/N2 gas composition. A long duration (~10 h) positive ionospheric storm with a maximum ΔVTEC% of 26.3% was observed during the second main phase (Dst=-124 nT) which lasted well into its recovery. This is mainly due to the combined effect of PPEFs associated with the long duration of southward turning of Z - component of the interplanetary magnetic field of the second main phase and DDEFs of the first main phase. L1 and L2 band scintillations did not occur during both the phases of storm implying that ionospheric irregularities do not necessarily occur under severe geomagnetic storms. However, two events of nighttime scintillations one before and other after the storm were observed.

Item Type: Journal Article
Uncontrolled Keywords: GPS TEC, Ionopshere, Solar flare, Geomagnetic storm, Ionospheric storm
Subjects: Q Science > QC Physics
Divisions: Faculty of Science, Technology and Environment (FSTE) > School of Engineering and Physics
Depositing User: Fulori Nainoca - Waqairagata
Date Deposited: 09 Dec 2020 11:50
Last Modified: 09 Dec 2020 11:50
URI: http://repository.usp.ac.fj/id/eprint/12474
UNSPECIFIED

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