Statistical Study of foF2 Diurnal Variation at Dakar Station from 1971 to 1996: Effect  of Geomagnetic Classes of Activity  on Seasonal Variation at Solar  Minimum and Maximum

Nour, Ali Mahamat; Ouattara, Frédéric; Louis, Zerbo Jean; Frédéric, Gyébré Aristide Marie; Nanéma, Emmanuel; Zougmoré, François

doi:10.4236/ijg.2015.63014

Cited by 6 publications

(2 citation statements)

References 16 publications

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“…At nighttime (from 0.00 LT to 04.00 LT and from 20.00 LT to 24.00 LT), electron surface density is higher on winter than that on summer. This last result highlights winter anomaly phenomenon (Ouattara et al, 2012;Nour et al, 2015).…”

Section: Resultsmentioning

confidence: 55%

Electron Bulk Surface Density Variability in Ionosphere during Quiet Days at Low Latitudes

Drabo¹,

Nanéma²,

Zerbo³

et al. 2019

APR

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This work deals with electron surface density time variation in ionosphere region. The study uses international reference ionosphere (IRI) model for investigation. Total Electron Content (TEC) parameter is carried out at different levels in the F2-layer of ionosphere. The study takes place at Ouagadougou station (12,4°N and 358,5°E), in West Africa. Quiet time periods of solar cycle 22 are considered. This study considers only the maximum and minimum phases of solar cycle 22. The five quietest days of the characteristic months in each season are used in the study. Seasonal time profiles of ionosphere parameters highlight relation between Total Electron Content (TEC) and Height of F2-layer (hmF2) in ionosphere region. The results found in this study correlate closely with parameters behavior previously found in other works.

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Section: Resultsmentioning

confidence: 55%

Electron Bulk Surface Density Variability in Ionosphere during Quiet Days at Low Latitudes

Drabo¹,

Nanéma²,

Zerbo³

et al. 2019

APR

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“…. It emerges from this study that in general, equinoctial asymmetry is less pronounced at Dakar station [35] and somewhere is absent during day time for all solar cycle phases. Equinoctial asymmetry is due to an asymmetry of ionization during both equinoxes, despite the fact that solar zenithal angle kept the same characteristics during both equinoxes.…”

Section: Discussionmentioning

confidence: 64%

foF2 Seasonal Asymmetry Diurnal Variation Study during Very Quiet Geomagnetic Activity at Dakar Station

Sandwidi

Gnabahou

Ouattara

2020

International Journal of Geophysics

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This paper aims to study the foF2 seasonal asymmetry diurnal variation at Dakar station from 1976 to 1995. We show that equinoctial asymmetry is less pronounced and somewhere is absent throughout 21 and 22 solar cycles. The absence of equinoctial asymmetry may be due to Russell-McPherron mechanism and the vertical drift E × B . The solstice anomaly or annual anomaly is always observed throughout both 21 and 22 solar cycles as measured at Dakar ionosonde. The maximum negative value of σfoF2, fairly equal to -65%, is observed during the decreasing phase at solstice time; this value appeared usually at 0200 LT except during the maximum phase during which it is observed at 2300 LT. The maximum positive value, fairly equal to +94%, is observed at 0600 LT during solar minimum at solstice time. This annual asymmetry may be due to neutral composition asymmetric variation and solar radiation annual asymmetry with the solstice time. The semiannual asymmetry is also observed during all solar cycle phases. The maximum positive value (+73%) is observed at 2300 LT during solar maximum, and its maximum negative (-12%) is observed during the increasing phase. We established, as the case of annual asymmetry, that this asymmetry could not be explained by the asymmetry in vertical velocity E × B phenomenon but by the axial mechanism, the “thermospheric spoon” mechanism, and the seasonally varying eddy mixing phenomenon.

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Annual and Diurnal Variabilities in the Critical Frequency (foF2) during Geomagnetic Fluctuating Activity over Solar Cycles 21 and 22 at Ouagadougou

Diabaté¹,

Ouattara²,

Zerbo³

2018

ACS

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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.

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Statistical Study of foF2 Diurnal Variation at Dakar Station from 1971 to 1996: Effect of Geomagnetic Classes of Activity on Seasonal Variation at Solar Minimum and Maximum

Cited by 6 publications

References 16 publications

Electron Bulk Surface Density Variability in Ionosphere during Quiet Days at Low Latitudes

Electron Bulk Surface Density Variability in Ionosphere during Quiet Days at Low Latitudes

foF2 Seasonal Asymmetry Diurnal Variation Study during Very Quiet Geomagnetic Activity at Dakar Station

Annual and Diurnal Variabilities in the Critical Frequency (foF2) during Geomagnetic Fluctuating Activity over Solar Cycles 21 and 22 at Ouagadougou

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