Abstract
Geomagnetic activity is characterized by four solar wind conditions. Each condition has specific impact on ionosphere. This paper review on fluctuating activity effects on ionosphere F2 layer through its critical frequency foF2 variations. Under fluctuating wind conditions, we have investigated on annual, diurnal and seasonal variations of foF2 during solar cycles 21 and 22 phases covered by Ouagadougou ionosonde station data (Lat: 12.5°N; Long: 358.5°E; dip: 1.43°). Our investigations show that foF2 annual’ variability is in phase with solar cycle. The diurnal variation is “noon bite out” most of the time except for the solar maximum where we have a morning peak testifying to the fact that the vertical drift E × B is disturbed. The seasonal variations show that the fluctuating activity has no particular effect on certain characteristics of the equatorial ionosphere such as electrojet and vertical drift E × B. However, the increase of the electric field pre-reversal phenomenon in autumn is a characteristic effect observed during the fluctuating activity.
Highlights
IntroductionMany studies have reviewed on ionosphere variability in equatorial region; some of them have pointed out the fact that this variability depend on solar cycle, season and geomagnetic activity [1] [2]
The seasonal variations show that the fluctuating activity has no particular effect on certain characteristics of the equatorial ionosphere such as electrojet and vertical drift E × B
The increase of the electric field pre-reversal phenomenon in autumn is a characteristic effect observed during the fluctuating activity
Summary
Many studies have reviewed on ionosphere variability in equatorial region; some of them have pointed out the fact that this variability depend on solar cycle, season and geomagnetic activity [1] [2]. This variability is supposed to be linked with its electric current and electric field which have effect on the critical frequency foF2. Previous studies deal with 1) foF2 time variation during quiet solar activity over season for solar minimum, and high and moderate period 2) foF2 statistical variability over seasons and solar cycle phases and 3) foF2 variability during disturbed periods
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