Association of depletions, enhancements and quasi-periodic variations in TEC with amplitude scintillations

Several TEC depletions associated with amplitude scintillations are reported from the Waltair observing station located between the equator and the anomaly-crest region. The characteristics of the TEC depletions are discussed, and statistics are given regarding the amplitude and duration of the depletions and their diurnal, seasonal, and solar-cycle dependences. Faraday rotation and scintillation data are derived from 136-MHz radio-beacon signals, and a typical 1-day record shows that scintillations accompany Faraday-rotation depletions and TIDs are preceded by TEC depletions. The amplitude scintillations occur more frequently than TEC depletions, and the duration of depletions typically ranges from 5 to 20 min. The amplitude of depletion ranges from 1 to 9 TEC units in the summer months and 1-8 units in the other seasons although 1-4 units is the most likely depletion in the equinox and winter seasons.