Equatorial and Low-Latitude Ionospheric Response to the Extreme Space Weather Event of March 2015, in the Brazilian Sector.

Abstract:

Fagundes PR, Cardoso FA and Venkatesh K

Physics and Astronomy Laboratory, Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, Sao Paulo, Brazil

 

In the present investigation we discuss the results on the response of the ionosphere (F-region) in the Brazilian sector, during extreme space weather event of March 2015. This geomagnetic storm has been considered as one of strongest storms in the solar cycle 24 where, the Dst index reached a minimum of −227 nT at 23:00 UT (17/03/2015) with KP reaching to 8^-, and the monthly mean F10.7 solar flux was 125 sfu. This space weather event was studied using a large network of 110 GPS stations. It has been noticed that the Total Electron Content (TEC) was severely disturbed during the geomagnetic storm main and recovery phases.

A wavelike oscillation with three peaks is observed from equator to low latitudes during the storm main phase on 17^th and 18^th March, 2015. Using a latitudinal chain of 8 GPS stations from equatorial region to low latitudes the storm time behavior of the Equatorial Ionization Anomaly (EIA) is investigated. It was noticed that the wavelike oscillation peak latitudinal extent decreases from the beginning of main phase to the recovery phase. The first maximum extends beyond from 2^oS to 20^oS, the second one from 8^oS to 18^oS and the third one from 13^oS to 17^oS. In addition, a strong negative phase in TEC variations is observed during the recovery phase on March 18, 2015. This negative phase is found to be stronger at low-latitude compared to the equatorial region. An anomalous behavior of EIA caused by the wavelike oscillations is observed during the main phase on March 17, 2015. Also, due to the strong negative phase in TEC resulted in strong EIA suppression on March 18, 2015.