Analysis of ionospheric features in middle and low latitude region of China during the geomagnetic storm in March 2015

The strongest geomagnetic storm of the current solar cycle occurred on 17 March 2015, with a minimum Dst index of -233 nT. In this paper, we reported the ionospheric disturbances in the middle and low latitude region of China during this storm. Here we utilized ionosondes data (f(0)F(2) and h(m)F(2)) and BDS GEO TEC from our 4 stations in Beijing, Wuhan, Shaoyang and Sanya, along with GPS S4 index. Possible mechanisms responsible for the ionospheric disturbances characterized by a positive storm followed by a long duration strong negative storm were discussed. Observations and analysis showed that during the daytime of March 17, the positive storm in the middle latitude was caused by neutral wind which uplifted the ionosphere, while the positive storm in the low latitude and near the northern equatorial ionization anomaly (EIA) was mainly caused by eastward prompt penetration electric field (PPEF). The long-lasting negative storm during the daytime of March 18 was due to westward disturbance dynamo electric field (DDEF) as well as neutral composition disturbances. During the nighttime of March 17 and 18, the negative storm and the absence of spread-F and ionospheric scintillation could be caused by the suppression of eastward electric field after the sunset and the equatorward wind surge, which pushed the EIA towards the equator. This was the first research related to ionospheric storm based on BDS GEO TEC network.