Pages: (1-13 )
Abstract
The F2-layer critical frequency (foF2) variability was investigated over Jicamarca (11.9oS, 76.8oW, dip 1oN), a station along the equator anomaly trough during solar minima period. Diurnally, foF2 is more vulnerable to variability during the nighttime (13-27%) than the daytime (5-16%) having two characteristic peaks: pre-sunrise and post-sunset peaks. The highest values were attained during the pre-sunrise peak with a value range of 24-34%. Seasonally and annually, the pre-sunrise peak is higher than the post-sunset peak. The nighttime downward reversal value in vertical plasma drift coincides with the enhanced foF2 variability. The rapid faster electron drift away from the equator is responsible for the sharp drop in NmF2 and a subsequent rise in the percentage variability coefficient immediately after sunset in all seasons. Seasonal peaks in foF2 variability are suspected to be controlled by the enhanced E x B drifts and atmospheric wind which is consistent with some earlier results obtained in some stations in the African region during solar minima periods.
Keywords: Pre-reversal enhancement; variability coefficient; foF2; solar minima; E x B drifts,