Ionospheric irregularities during geomagnetic storms near the southern crest of the EIA in South America

Gilda González - National University of Tucumán

Session:  Thermosphere-Ionosphere Interactions and Effects

Abstract

We present the analysis of the occurrence of ionospheric irregularities during three geomagnetic storms at a low latitude station in the Southern American longitudinal sector ( 26.9 ° S, 294.6 ° E; magnetic latitude 15.5 ° S), near the southern crest of the equatorial ionization anomaly (EIA). The geomagnetic storms occurred on May 27, 2017 (low occurrence rates of spread-F), October 12, 2016 (transition from low to high occurrence rates of spread-F) and November 7, 2017 (high occurrence rates of spread-F). We used data from Global Positioning System (GPS) receivers and ionosondes. We analyzed the rate of change of total electron content (TEC) Index (ROTI), GPS Ionospheric L-band scintillation, the virtual height of the F-layer bottom side (h'F) and the critical frequency of the F2 layer (foF2). Each ionogram is examined for the presence of spread-F.

We observed that geomagnetic activity creates favorable conditions for the initiation of ionospheric irregularities. Post-midnight irregularities are developed due to the presence of eastward disturbance dynamo electric fields (DDEF). For the May storm, an eastward over-shielding prompt penetration electric field (PPEF) is also acting. This PPEF is added to the DDEF and produces the uplifting of the F region that helps trigger the irregularities.