Investigation of Geomagnetic Storm Effects to Ionosphere over Pontianak: A Study Case

We study the effect of magnetic storms to the low-latitude ionosphere by analyzing theionospheric data over Pontianak station that located at the geographic equatorial. Two cases of strong geomagnetic storms on March 17, 2015, and April 24, 2023, will be discussed. This study used ionospheric observation data foF2, TEC, and S4 index; geomagnetic activity of SYMH-H, AE index, and Dst index; and the north–south component of interplanetary magnetic field and interplanetary electric field dawn-dusk component. From the TEC data, the vertical TEC were calculated and then the mean VTEC values for the five geomagnetically quiet days in the month associated with the two storm events were calculated. The deviation of VTEC from the mean during geomagnetically quiet days for both storms shows a decreasing of VTEC values about 10 h after the minimum values of Dst index. Also, during the SSC of March 17, 2015, storm, a large negative deviation in the VTEC data is observed, while for the April 24, 2023, storm, only a slight increase is observed. An increase in the S4 index occurred during the recovery period of the April 2023 storm but not occurred for March 2015 storm. Our tentative conclusion is that the increase in the S4 index during the recovery phase of the magnetic storm may be due to the prevention of scintillation as a consequence of increased magnetic activity in the mid-latitudes.