Storm-time observations of traveling ionospheric disturbances and ionospheric irregularities in East Africa

In this paper equatorward propagating large scale traveling ionospheric disturbance (LSTID) on 17 March 2015 were investigated using the Statistical Angle-of-Arrival and Doppler Method for GPS (SADM-GPS) radio interferometry technique in data-scarce East Africa. To apply the SADM-GPS method, 5 GPS arrays each with 3 GPS receivers arranged in a triangular geometry were used. Our results show that during 15:00-18:00 UT on 17 March, TIDs with mean horizontal velocities between 161.9 and 464.4 m/s were observed. Using the wavelet analysis, the periods of TIDs in a range of 51-69 min that qualify to LSTIDs were revealed. The peak-to-peak phase shift of detrended total electron content (TEC) over latitudes in this study confirms the equatorward TID propagation, which was obtained by the SADM-GPS technique. A pair of magnetometers were used to infer E × B drift and an adequate agreement was found with Swarm satellites derived plasma density that enabled us to explain the behaviour of ionospheric irregularity during the main phase of the geomagnetic storm. Moreover, significant TEC enhancement (reaching ∼20%-105%) were captured by GPS arrays during the period of TID propagation. Nevertheless, the rate of change of TEC (ROT) and ROT index (ROTI) show wavy structures that reflect TID effects over ionospheric modulations during the post noon to evening hours of 17 March 2015.