VERTICAL PLASMA DRIFTS ESTIMATED FROM IONOSPHERIC F2-REGION REAL HEIGHTS AT A LOW LATITUDE STATION DURING LOW SOLAR ACTIVITY

Abstract

Vertical plasma drift velocities (v_z) estimated from peak heights of F2-region (hmF2) was investigated over Ilorin (lat. 8.31°N, long. 4.34°E, dip lat. 2.95o N) during a year of Low Solar Activity (LSA), a station sited at the low latitudinal dip. The monthly means of vertical plasma drifts, v_z were estimated from 10-international quiet days (IQDs) monthly means of hmF2 computed across each local time hour. Diurnally, v_z had behavourial patterns of pre-noon and post-noon peaks, but in hmF2, it had pre-noon and post-sunset peaks occurred for all seasons. The v_z pre-noon peak magnitudes are 1.0, 2.4 and 6.4 m/s for December Solstice, June Solstice and Equinox respectively; and v_z post-noon peak magnitudes are 0.6, 1.7 and 2.2 m/s for December Solstice, Equinox and June Solstice respectively. The hmF2 pre-noon peak magnitudes is (316–353) km, and post-sunset peak magnitudes is (310–392) km for all seasons. Also, v_z displayed pre-reversal enhancement (PRE) night peaks for all seasons. The PRE peak magnitudes are [(-0.1) – (-1.2)] m/s at 2000 LT, [(-0.2) – (-4.0)] m/s at 2200 LT, [(-0.6) – (-3.0)] m/s at 0000 LT and [(-0.5) - (-1.8)] m/s between 0300 LT and 0400 LT respectively for all seasons. The same phenomenal occurrence was noticed in the annual patterns of hmF2 and v_z. In general, the v_z and hmF2 magnitudes were highest in equinox (6.4 m/s and 353 km) and lowest in solstice (1.0 m/s and 310 km). The v_z and hmF2 steady and incessant drop shows the rapidly drifting away of electrons from the equator caused by solar ionization in the low latitude region for all seasons.