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

Guibula, Karim; Ouattara, Frédéric; Gnabahou, Doua Allain

doi:10.4236/ijg.2018.94013

Cited by 7 publications

(2 citation statements)

References 11 publications

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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: 67%

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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Section: Results and Discussion:-supporting

confidence: 67%

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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“…Phases. For the determination of solar phases, we have used the new sunspot number changes which are fully described in [5,6] following criteria adopted by [7][8][9][10]: (1) minimum phase: Rz < 20; (2) ascending phase: 20 ≤ ≤ 100 and higher than that of the previous year; (3) maximum phase:…”

Section: Criteria For Determining the Solar Cyclementioning

confidence: 99%

Critical Frequency foF2 Variations at Korhogo Station from 1992 to 2001 Prediction with IRI-2012

Guibula

Zerbo

Ouattara

2019

International Journal of Geophysics

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In this paper we report the foF2 data measured at Korhogo station (Lat. 9.3° N; Long. 354.6° E; dip. 0.6° S) compared to predictions with IRI-2012 subroutine URSI and CCIR for different solar cycle phases (minimum, ascending, maximum, descending) and different geomagnetic activity classes (quiet, fluctuating, recurrent, shock). According to our investigations, predictions with IRI are in agreement with the measured data during daytime and show significant differences between them at night-time and especially before sunrise. Except at solar minimum, the gap between predictions and measured data are more appreciable during recurrent and shock conditions compared to quiet and fluctuating conditions. Our results also show that only URSI model expresses the signature of EXB drift phenomenon at solar maximum phase during the recurrent days and at ascending phase for fluctuating activity.

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

Cited by 7 publications

References 11 publications

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

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

Critical Frequency foF2 Variations at Korhogo Station from 1992 to 2001 Prediction with IRI-2012

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

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