Responses of ionosphere over south China to some ICME- and CIR-driven storms in four different phases of solar cycle 24 and the associated disturbance electric field

Interplanetary coronal mass ejections (ICME) and corotating interaction regions (CIR) can alter the parameter of solar wind velocity and interplanetary magnetic field (IMF) which cause the different responses of low and equatorial ionosphere to ICME- and CIR-driven storms. This study has investigated the responses of ionosphere over south China to four combinations of ICME- and CIR-driven storms occurred in four different phases of solar cycle 24, using parameters such as equatorial electrojet (EEJ), Total Electron Content (TEC) deviations and the average rate of change of TEC index ((Formula presented) ). The main results reveal that different solar wind structures appeared in different signals of solar wind velocity (Formula presented). Combined PPEF (the prompt penetration of Interplanetary Electric Field to low-latitude) eastward convection electric field and DDEF (the disturbance dynamo electric field) dominated over south China during ICME- and CIR-driven storm main and recovery phases. But the effects of DDEF is more dominant during CIR- driven storm main phase compared to during ICME-driven storm main phase. Negative ionospheric storm effects were observed from ΔTEC (exceeding −25%) matching with negative TEC deviations during ICME- and CIR-driven storms in declining phase of solar cycle 24, which could be attributed to the decreases in thermospheric neutral composition (Formula presented) and the effects of PPEF and DDEF. Ionospheric irregularities with (Formula presented) greater than (Formula presented) were observed during CIR-driven storm main and recovery phases in all active phases of solar cycle 24, and 3 h prior to ICME-driven storm main phase in minima phases of solar cycle 24.