Solar Activity and Temporal Dependence of Rate of Change of Ionospheric Total Electron Content in Low-Latitude Region

Ionospheric plasma irregularities over the Philippines are observed using GNSS receivers in Metropolitan Manila during low and high solar activities. Using high-rate (1 Hz) GNSS data, 5-minute the rate of change of total electron content (ROTI) in TECU/min is calculated. Mean values of ROTI show that >0.5TECU/min indicate the presence of ionospheric plasma irregularities and could reach to more than 5 TECU/min during large events. They are typically observed between post-sunset to post-midnight hours (2000-0200LT, 1200-1800UT) and during equinoctial months. The duration of events and month occurrence increases as solar activity increases, where occurrence can extend to summer months. The results have been consistent to previous researched but requires more in-depth analysis by inclusion of parameters related to these irregularities, additional stations and extended observation years to cover the whole of a solar cycle.