Ionospheric dynamics of two geomagnetic storms at South America sector

The ionospheric dynamics at South America (SA) sector during the two strongest geomagnetic storms of the 24th solar cycle is investigated; one of them occurred within the period from 15 to 20 March 2015, and the other one, from 21 to 25 June 2015. The ionospheric analysis includes total electron content and F2-layer critical frequency, using GNSS receivers and ionosondes instruments from low to high latitudes at SA stations. Preliminary results show that geomagnetic storm started on 17/03/2015 at 6:00 UT, reaching -220 nT in the negative phase, classifying the geomagnetic storm as “Intense”. The Kp index reached 6 and was classified as “Very Disturbed”, and on the same day the AE index reached 1700 nT. According to the variation of the magnetic field, the recovery phase started on 18/03/2015, as shown by the Embrace Magnetometer Network. In the ionograms the storm affected the critical frequency of plasma in the foF2 layer, compared to the day before the storm there was little variation. The most altered ionogram was from the city of Fortaleza - CE (15/03/2015 22:00 UT) with a value of (15Mhz), local time 17: 00h. The TEC variation for the geomagnetic storm of 17/03/2015. Instruments such as Global Navigation Satellite System (GNSS) receivers and ionospheres are important tools for investigating the ionospheric response to a geomagnetic storm (Correia et al., 2017; Yizengaw et al., 2005; Mendillo et al., 2000; Skone et al., 2000). Investigations were conducted by Mansilla et al. (2018) using GNSS receivers to analyze the Total Electron Content (TEC) due to the June 2015 storm in a global context, showing important CETs at mid-latitude stations throughout the Northern Hemisphere (summer) during the development of the main phase. At equatorial and low latitudes, at the beginning of the geomagnetic storm, there were increases in CET due to PPEF. Such increases were also observed in the Southern Hemisphere (winter).