Spread-F occurrence during geomagnetic storms near the southern crest of the EIA in Argentina

This work presents, for the first time, analysis of occurrence ionospheric irregularities during geomagnetic storms at Tucumán, Argentina, a low latitude station in Southern American longitudinal sector (26.9°S, 294.6°E; magnetic 15.5°S) near southern crest equatorial ionization anomaly (EIA). Three occurred on May 27, 2017 (a month rates spread-F), October 12, 2016 transition from to high spread-F) and November 7, are analyzed using Global Positioning System (GPS) receivers ionosondes. The rate change total electron content (TEC) Index (ROTI), GPS Ionospheric L-band scintillation, virtual height F-layer bottom side (h'F) critical frequency F2 layer (foF2) considered. Furthermore, each ionogram is manually examined presence spread-F signatures. results show that, three events studied, activity creates favorable conditions initiation irregularities, manifested by TEC fluctuation. Post-midnight may have due eastward disturbance dynamo electric fields (DDEF). For storm, an over-shielding prompt penetration field, (PPEF) also acting. A possibility that PPEF added DDEF produces uplifting F region helps trigger irregularities. Finally, November, strong L band scintillation observed associated with range (SSF), is, extending bottom-side topside region.