Ionospheric plasma structuring and propagation over India during 8 September

Abstract:

The series of X and M class flares and associated Coronal Mass Ejections (CMEs) occurred on the first days of September 2017 induced significant perturbations on the low-latitude ionospheric electrodynamics. On 8 September in the Indian sector, the storm caused a severe modification of the equatorial electrojet (EEJ) with a consequent variation of the ionospheric structuring and dynamics. In our analysis we propose an original method to isolate and identify the EEJ variations from the geomagnetic data and we detect the presence of equatorial plasma bubbles (EPB) from L-band TEC data and understand their movement. Our results provide evidence of independent EPBs appearance freshly generated and inherited from a migrating plasma structure. The EPB (or EPBs) occurring in the south is freshly generated just above the magnetic equator, likely triggered by the sudden increase of EEJ just before the pre-reversal enhancement (PRE). The EPB appearing in the North-East Indian region is associated with a migrating structure, resulting to move northward with a velocity of about 650 m/s, possibly testifying the passage of a Large-Scale Travelling Ionospheric Disturbance (LSTID). The occurrence of severe post-sunset scintillations in the northeaster sector suggests a possible cascade process forming small-scale irregularities from the migrating EPB.