Ionospheric electron content depletion associated with amplitude scintillation at the equatorial anomaly crest region

The diurnal and seasonal behaviors of the ionospheric total electron content (TEC) depletion associated with VHF amplitude scintillation observed at Lunping, Taiwan (25.00 deg N, 121.17 deg E geographic), during the period March 1977 to February 1980 were presented. Diurnally, the maximum occurrence of TEC depletion appears during the late evening hours for all seasons except winter. Seasonally, the maximum occurrence of TEC depletion is not fixed at a certain season but varies with sunspot number because of the different sunspot number dependence of the occurrence of TEC depletion in different seasons. The most probable maximum TEC depletion ranges from 0.8 to 3.6 x 10 to the 16th el/sq m, and the duration ranges from 10 to 33 min. No correlation was found between the maximum TEC depletion and the duration or between the maximum TEC depletion and the associated ionospheric scintillation index. The association between TEC depletion and range spread F is much better than that between TEC depletion and frequency spread F. 32 references