Emergence of a localized total electron content enhancement during the G4 geomagnetic storm of September 8, 2017

Abstract

Abstract. In this work, the first results of the analysis on total electron content (TEC) data before, during and after the geomagnetic storm of September 8, 2017 are reported. A common response to geomagnetic storms due to the southern vertical interplanetary magnetic field (Bz) is the enhancement of the electron density in the ionosphere. Vertical TEC (VTEC) from the Center for Orbit determination in Europe (CODE) along with a statistical method were used to identify positive and/or negative ionospheric storms in response to the geomagnetic storm of September 8, 2017. When analysing the response to the G4 storm of September 8, 2017 it was indeed possible to observed an enhancement of the equatorial ionization anomaly (EIA); however what it is was unexpected, was the identification of a local TEC enhancement (LTE) to the south of the EIA (~ 40° S), right over New Zealand and extending towards the south-eastern coast of Australia and also eastward towards the Pacific). This was a very transitory LTE that lasted approximately 2 hours, starting at ~ 02:00 UT on September 8 where its maximum VTEC increase was of 241,2 %. Using the same statistical method we looked for LTEs in a similar category geomagnetic storm, the G4 storm of St. Patrick's day of 2015; however for this storm, no LTEs were identified. As also indicated in a past recent study for the August 15, 2015 geomagnetic storm, an association between the LTE and the excursion of Bz observed during the September 8, 2017 storm is observed. Nevertheless, it is more likely that a direct impact of the super-fountain effect along with another ionospheric physical mechanism may be playing an important role in the production of this LTE.

Topside Ionospheric Conditions During the 7–8 September 2017 Geomagnetic Storm

“…The MET TEC results showed a later storm time TEC increase between 0200 UT and 0600 UT. These daytime observations during the main phase were consistent with the ground-based observations (Beltran, 2018;Lei et al, 2018). Since the maximum TEC enhancements at~0000 UT on 8 September were subsequent to the southward turning of IMF-B z , intensified AE, and sudden decrease in Dst at~2330 UT on 7 September (Figures 1a-1c), it indicates that the TEC enhancements during the first main phase of the storm may be most likely associated with undershielding PPEF.…”

Analysis of the EGNOS quality parameters during high ionosphere activity

“…One of the common responses to a geomagnetic storm caused by the penetration of the southward interplanetary magnetic field is a significant increase of the TEC, in the equatorial and mid‐latitude regions, which manifests as an enhancement of the equatorial ionisation anomaly (EIA). Such increase of TEC in the EIA is possible to visualise in global ionospheric maps (GIMs), which were already presented for examined periods by Sotomayor–Beltran in 2017 [33]. For the purposes of this research, the vertical TEC (VTEC) over investigated IGS stations in examined periods were calculated and presented in Figs.…”