Nighttime morphology of vertical plasma drifts at Ouagadougou during different seasons and phases of sunspot cycles 20–22

Abstract

The nighttime morphology of vertical plasma drift (Vd) inferred from ground‐based measurements of the F layer height at Ouagadougou (12.4°N, 358.6°E) in the African Equatorial Ionization Anomaly trough was investigated. The observation covers four seasons, four sunspot cycle phases, annual, and 11 year sunspot cycle (SC) variations of the SCs 20–22 spanning 1966–1998 and a first attempt of such study. The annual mean peak magnitudes of Vd during the prereversal enhancement (PRE) and minimum reversal periods exhibit the 11 year sunspot cycle evolution with the sunspot number (Rz). The PRE peak/Rz and reversal peak/Rz relationships are 98.7% and 84.8%, respectively. PRE peak in June solstice appears 1 h later than for other seasons and is attributed to a decrease in the equatorial zonal wind/conductivity gradient. The highest PRE magnitude and downward perturbation drifts near dusk appear during the equinoxes and lowest in June solstice for all cycles. There is semiannual asymmetry in the variation of Vd during all cycles of the PRE event with peaks in March and September/October. A remarkable feature is the consistent local presunrise drift enhancement for two SCs 20 and 21, which is not a regular feature of the equatorial ionosphere. The rate of inhibition of scintillation effect increases with decreasing phase of sunspot activity and maximizes during the solstices. Both the PRE and minimum reversal peak magnitudes are influenced by the phase of sunspot cycle. Ouagadougou data in this study had shown reliable drift characteristics and can be integrated into the African regional empirical drift model.

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

“…Rishbeth et al (2000) and the references therein attributed the seasonal variations in the ionosphere to changes in the neutral air composition due to the large-scale thermospheric dynamics, changes in atmospheric turbulence, inputs from atmospheric waves, and variations in geomagnetic activities. Several authors, including Quattara et al (2009) and Adebesin et al (2015), have reported distinct seasonal variations, similar to our findings, in the equatorial ionosphere in the western African region using ionosonde measurements.…”

The interplanetary and magnetospheric causes of extreme dB/dt at equatorial locations

“…Ngwira et al [] did an extended global study on the work of Pulkkinen et al [] using 12 severe geomagnetic storms and investigating the influence of the equatorial electrojet (EEJ) on the enhanced induced geoelectric fields over ionospheric stations around the dip equator among other findings. The EEJ is a thin strip of enhanced eastward current flowing around 110 km height of the E region cutting across ±3 of the dip equator and subsequently leading to the F 2 region equatorial ionisation anomaly [ Adebesin et al, , ]. Ngwira et al [] reported higher enhanced induced geoelectric fields (or d B/ d t ) at stations within the EEJ strip than at stations outside the strip.…”

F2-layer height of the peak electron density (hmF2) dataset employed in Inferring Vertical Plasma Drift – Data of Best fit

“…The months were then classified into different seasons viz: March equinox (February, March April), June solstice (May, June, July), September equinox (August, September, October) and December solstice (November, December, January) (e.g. [4] ) for further drift analysis.…”