PRE-REVERSAL ENHANCEMENT IN THE EQUATORIAL E AND F REGION ELECTRON DRIFT, VELOCITIES AND ITS SEASONAL VARIATION - AN EXPLANATION

Horizontal drift velocity of electrons in the E-region and their vertical drift velocity in the F-region in the equatorial ionosphere, show regular enhancements, prior to the morning and evening drift reversals. These enhancements are more pronounced prior to the evening reversal, than prior to the morning reversal, and also show considerable seasonal variations. Based on the analysis of electron drift data obtained at Jicamarca, Peru using the VHF radar, an explanation for the pre-reversal enhancement and its seasonal variations is attempted here. The explanation is based on the effects of geomagnetic and solar declination angles on the electrodynamic coupling of non-equatorial and equatorial E- and F-regions of the ionosphere.