Variation of Equatorial Estimated Vertical Ion Drifts During Low Solar Activity

Abstract

Vertical ion drifts (v_z) estimated from F2-region peak heights was studied under the condition of international quiet days (IQDs) over Ilorin (lat. 8.31°N, long. 4.34°E, dip lat. 2.95^o) during low solar activity (LSA), a station located at the equatorial dip. The 10-international quiet days (IQDs) monthly means across each local time hour were used for the estimation.  featured to two characteristics: the pre-noon and the post-noon peaks in the seasonal patterns.  pre-noon peak magnitudes are 1.0, 2.4 and 6.4 m/s for December Solstice, June Solstice and Equinox respectively between 0700 LT and 0900 LT; and  post-noon peak magnitudes are 0.6, 1.7 and 2.2 ms^-1 for December Solstice, Equinox and June Solstice respectively at 1700 LT. Another  feature noticed is slight-transitory enhancement spikes in seasonal order with magnitudes of December (0.4 ms^-1) and June (0.5 ms^-1) Solstices, and Equinox (1.0 ms^-1) between 1200 LT and 1300 LT. Finally,  featured pre-reversal enhancement (PRE) night peaks in all seasons. The PRE peak magnitudes are [(-0.1)–(-1.2)] ms^-1 at 2000 LT, [(-0.2)–(-4.0)] ms^-1 at 2200 LT, [(-0.6)–(-3.0)] m/s at 0000 LT and [(-0.5)–(-1.8)] ms^-1 between 0300 LT and 0400 LT respectively in all seasons. Similar phenomenal observation was noticed in the  annual pattern. In general,  magnitudes were greatest in Equinox (6.4 ms^-1) and least in Solstice (1.0 ms^-1). The continual steady fall in  is caused by the speedily moving away of electrons from the equator due to solar ionization in all seasons.