Study of ionospheric response to geomagnetic storms on 27–29 May 2017 and 18–20 February 2014 along different longitudes

The study examines the change in the vertical total electron content (VTEC) and the presence of ionospheric irregularities during the geomagnetic storms that occurred on February 18–20, 2014 and May 27–29, 2017. TEC data from satellite receivers located in the equatorial and low latitude areas of the Americas, Pacific, Africa, and India were analyzed. In addition, magnetometer data, the Direct Penetration of Equatorial Electric Field Model (PPEEFM), interplanetary magnetic fields, and electric field data were also used. The Rate of TEC change (ROTI) was used to investigate changes in TEC caused by disturbances. The results indicate that there was a significant increase in TEC $\approx 150$ % over the Indian sector on 29 May 2017. Similarly, during the recovery phase of the storm there was an increase in TEC (about 240 %) over the Pacific sector which may attributed disturbances in the magnetosphere and ionosphere currents. During the geomagnetic storm on February 19–20, 2014, there were noticeable positive storm effects over the American sector, with TEC deviations of up to 220 %. After the main storm phase, the Pacific sector experienced TEC deviations of around 300 %. The study also found that ionospheric irregularities were suppressed in the American, African, and Indian sectors during the storm period in May 2017, while the geomagnetic storm of February 18–20, 2014 led to irregularities in these sectors, with complete suppression over the Pacific sector. This effect on irregularities is likely attributed to changes in IMF Bz components polarity and the associated amount of energy supplied to magnetosphere-ionosphere system during the geomagnetic storms in May 2017 and February 2014.