Study and Modeling the Impact of June 2015 Geomagnetic Storms on the Brazilian Ionosphere

This study investigates the impact of geomagnetic storms that occurred on June 8, 22-23, and 25, 2015, on the ionosphere in the low-latitude and equatorial regions of Brazil. By examining various data sources, such as solar wind parameters from the ACE satellite, GPS vertical total electron content (VTEC), magnetometer data, and the SAMI2 model, we aimed to simulate the effects of storms on the ionosphere in these regions. Two methods were employed to separate DP2 and Disturbance dynamo (Ddyn) from the ionospheric disturbance current (Diono). Our analysis revealed a positive (negative) ionospheric storm in the VTEC during the main phase (recovery) of the June 22-23 and 25 storms. This observation can be attributed to the combined impact of the eastward prompt penetration of the magnetospheric convection electric field (westward disturbance dynamo electric field) and changes in the storm-time thermospheric [O]/[N_2] ratio based on the GUVI satellite imagery. Notably, the westward disturbance dynamo exhibited a significant amplitude on June 23 in Belem. The amplitude of the D_dyn at Belem (dip lat: - 0.47˚) was greater than that at Alta Floresta (dip lat: - 3.75˚) due to intensified cowling conductivity in Belem. Furthermore, we found that the SAMI2 model provided more accurate results when we replaced the default ExB drift with the vertical drift calculated from the ground-based magnetometer, enabling us to simulate the effect of the westward DDEF on VTEC during daytime.