Investigation on equinoctial asymmetry observed in Niamey Station Center for Orbit Determination in Europe Total Electron Content (CODG TEC) variation during ~ solar cycle 23

Ouattara, Frédéric; Zerbo, Jean Louis; Fleury, Rolland

doi:10.5897/ijps2017.4684

Cited by 7 publications

(13 citation statements)

References 26 publications

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“…It emerges from this study that in general, the equinoctial asymmetry is less pronounced and somewhere is absent during all solar cycle phases. This is an agreement with the conclusion of [1] results. These authors found that an equinoctial asymmetry is principal due to Russell-McPherron mechanism for all seasons (spring and fall).…”

Section: Discussionsupporting

confidence: 93%

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foF2 Seasonal Asymmetry Time Variation at Korhogo Station from 1992 to 2002

Guibula¹,

Ouattara²,

Gnabahou³

2018

IJG

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foF2 seasonal asymmetry is investigated at Korhogo station from 1992 to 2002. We show that equinoctial asymmetry is less pronounced and somwhere is absent trough out solar cycle phase. In general, the absence of equinoctial asymmetry may be due to the fact that in equinox and for each solar cycle phase, the asymmetry is due to Russell-McPherron mechanism. The solstice anomaly or annual anomaly is always observed throughout solar cycle phase. The minimum value of ΔfoF2 is inferior than −60% seen during all solar cycle phase at 0700 LT. This annual asymmetry may be due to interplanetary corpuscular radiation.

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Section: Discussionsupporting

confidence: 93%

“…The asymmetry observed in F2 layer critical frequency (foF2) or in the peak electron density (NmF2) of F2 layer or in the Total Electron Content (TEC) values time variation has been investigated by several authors (e.g. [1]- [7]).…”

Section: Introductionmentioning

confidence: 99%

foF2 Seasonal Asymmetry Time Variation at Korhogo Station from 1992 to 2002

Guibula¹,

Ouattara²,

Gnabahou³

2018

IJG

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“…The panels "a", "b", "c" and "d" present the graph of the spring, summer, autumn and winter seasons respectively. For all geomagnetic activities, the absence of equinoctial asymmetry is clearly highlighted and the figures show this results as those founded by Ouattara et al, (2017) at Niamey station and Guibula et al, (2018) at Korogho station. Figure 4 shows that, during FA, both graphs show an "R" profile during all seasons but it shows a "M" profile for winter season.…”

Section: Results and Discussion:-supporting

confidence: 63%

Comparative Study of the Geomagnetic Activity Effect on Fof2 Variation as Defined by the Two Classification Methods at Dakar Station Over Seasons

Sandwidi¹,

Gnabahou²,

Ouattara³

2020

IJAR

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For the present paper, data involved are: (1) foF2 values carried out at Dakar station. This station operated from 1950 to December 1996. The involved data interval for our study is 1976-1995 and concerned Solar Cycle 21 (SC 21) and Solar Cycle 22 (SC 22); (2) Zurich sunspot number (Rz), from OMNI data set http://omniweb.gsfc.nasa.gov/form/dx1.html for the influence of solar cycle phase and (3) Mayaud (1971, 1972, 1973, 1980) geomagnetic index aa for geomagnetic activity impacts. For this study, foF2 diurnal variation are analyzed by considering seasonal impacts. The seasons considered here are: (1) spring (March, April and May); (2) summer (June, July and August); (3) autumn (September, October and November) and (4) winter (December, January and February). Methods:-Seasons determination: The seasons are considered here as: (1) spring (March, April and May); (2) summer (June, July and August); (3) autumn (September, October and November) and (4) winter (December, January and February). Description of the two geomagnetic activity classification methods: Based on the strong correlation between geomagnetic index Aa (obtained from the following website: http://isgi.unistra.fr/data_download.php) and solar wind velocity established by Svalgaard (1977), Legrand and Simon

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“…Many mechanisms have been suggested to explain this asymmetry such as ionospheric electric field variation, geomagnetic activity, solar wind change through the equinoxes, thermosphere chemical composition asymmetric variation, and Russell-McPherron mechanism. [13] at Niamey station and [8] at the one of Korhogo suggest that the equinoctial asymmetry is mainly due to the Russell-McPherron mechanism for all seasons (spring and autumn) at those African equatorial anomaly regions of the ionosphere. Then, one can expect to have "no equinoctial asymmetry" during the equinox months.…”

Section: Discussionmentioning

confidence: 99%

“…Since the success of transatlantic radio transmission of Marconi in 1901, several studies on ionosphere parameter variation have been undertaken. Many of them focused on seasonal asymmetry observed in F2 layer parameters such as the peak electron density (NmF2), the total electron content (TEC), or the critical F2 layer frequency (foF2) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The present paper is aimed at investigating the asymmetry observed during equinoctial and solstice time at Dakar station (Lat: 14.8°N; Long: 342.6°E), an African Equatorial Ionization Anomaly (EIA) region station, by using foF2 values computed in this ionosonde station.…”

Section: Introductionmentioning

confidence: 99%

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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Investigation on equinoctial asymmetry observed in Niamey Station Center for Orbit Determination in Europe Total Electron Content (CODG TEC) variation during ~ solar cycle 23

Cited by 7 publications

References 26 publications

foF2 Seasonal Asymmetry Time Variation at Korhogo Station from 1992 to 2002

foF2 Seasonal Asymmetry Time Variation at Korhogo Station from 1992 to 2002

Comparative Study of the Geomagnetic Activity Effect on Fof2 Variation as Defined by the Two Classification Methods at Dakar Station Over Seasons

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

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