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Search Results: 1 - 10 of 193269 matches for " Frédéric Ouattara "
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Relationship between geomagnetic classes’ activity phases and their occurrence during the sunspot cycle
Frédéric Ouattara
Annals of Geophysics , 2009, DOI: 10.4401/ag-4634
Abstract: Four well known geomagnetic classes of activity such as quiet days activity, fluctuating activity, recurrent activity and shock activity time occurrences have been determined not only by using time profile of sunspot number Rz but also by using aa index values. We show that recurrent wind stream activity and fluctuating activity occur in opposite phase and slow solar wind activity during minimum phase and shock activity at the maximum phase. It emerges from this study that fluctuating activity precedes the sunspot cycle by π/2 and the latter also precedes recurrent activity by π/2. Thus in the majority the activities do not happen at random; the sunspot cycle starts with quiet days activity, continues with fluctuating activity and during its maximum phase arrives shock activity. The descending phase is characterized by the manifestation of recurrent wind stream activity.
foF2 Seasonal Asymmetry Time Variation at Korhogo Station from 1992 to 2002  [PDF]
Karim Guibula, Frédéric Ouattara, Doua Allain Gnabahou
International Journal of Geosciences (IJG) , 2018, DOI: 10.4236/ijg.2018.94013
foF2 seasonal asymmetry is investigated at Korhogo station from 1992 to 2002. We show that equinoctial asymmetry is less pronounced and somewhere 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.
Annual and Diurnal Variabilities in the Critical Frequency (foF2) during Geomagnetic Fluctuating Activity over Solar Cycles 21 and 22 at Ouagadougou  [PDF]
Abidina Diabaté, Frédéric Ouattara, Jean Louis Zerbo
Atmospheric and Climate Sciences (ACS) , 2018, DOI: 10.4236/acs.2018.84029
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.
The Effects of the Recurrent Storms on Fof2 at Ouagadougou Station during Solar Cycles 21-22  [PDF]
Wambi Emmanuel Sawadogo, Frédéric Ouattara, Mahammat Nour Ali
International Journal of Geosciences (IJG) , 2019, DOI: 10.4236/ijg.2019.101006
Abstract: The present paper deals with the effect of recurrent activity on the foF2 diurnal variation at Ouagadougou station for solar cycles 21 and 22. The recurrent activity produces at daytime positive storm for all solar cycle phases. For all seasons, the recurrent activity causes positive storm during nighttime and has no effect during daytime. From this study, it emerges that a positive effect of the storm at this station may be explained by the thermospheric composition changes. Recurrent activity more occurs during the solar decreasing phase and during spring month. The storm strength shows solar cycle phase and seasonal dependence. The storm strength is the highest during the solar increasing phase and during summer months.
The Geomagnetic Effects of Solar Activity as Measured at Ouagadougou Station  [PDF]
Aristide Marie Frédéric Gyébré, Doua Allain Gnabahou, Frédéric Ouattara
International Journal of Astronomy and Astrophysics (IJAA) , 2018, DOI: 10.4236/ijaa.2018.82013
Abstract: The coronal mass ejections (CMEs) produce by Sun poloidal magnetic fields contribute to geomagnetic storms. The geomagnetic storm effects produced by one-day-shock, two-days-shock and three-days-shock activities on Ouagadougou station F2 layer critical frequency time variation are analyzed. It is found that during the solar minimum and the increasing phases, the shock activity produces both positive and negative storms. The positive storm is observed during daytime. At the solar maximum and the decreasing phases only the positive storm is produced. At the solar minimum there is no three-days-shock activity. During the solar increasing phase the highest amplitude of the storm effect is due to the one-day-shock activity and the lowest is produced by the two-days-shock activity. At the solar maximum phase the ionosphere electric current system is not affected by the shock activity. Nevertheless, the highest amplitude of the storm effect is caused by the two-days-shock activity and the lowest by the one-day-shock activity. During the solar decreasing phase, the highest amplitude provoked by the storm is due to the three-days-shock activity and the lowest by the one-day-shock activity.
foF2 Diurnal Variability at African Equatorial Stations: Dip Equator Secular Displacement Effect  [PDF]
Doua A. Gnabahou, Frédéric Ouattara, Emmanuel Nanéma, Fran?ois Zougmoré
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.48108

The paper goal is to analyze the variability of foF2 at African equatorial stations and the effect of dip angle on this variability. The gap between the dip angle of Dakar and Ouagadougou is superior to that between Djibouti and Ouagadougou. The trend of the dip angle at Ouagadougou and Dakar decreases while that of Djibouti increases. The relative position of the station with respect to the equator and the trend sign explains the difference observed in foF2 variability at Dakar station and at the two other stations. At Djibouti and Ouagadougou, foF2 exhibits noon bite out profile during all solar cycle phases while at Dakar observed profile is dome or plateau during the maximum and the predominance afternoon peak for the other solar cycle phases.

Solar Activity and Meteorological Fluctuations in West Africa: Temperatures and Pluviometry in Burkina Faso, 1970-2012  [PDF]
Jean-Louis Zerbo, Frédéric Ouattara, Emmanuel Nanéma
International Journal of Astronomy and Astrophysics (IJAA) , 2013, DOI: 10.4236/ijaa.2013.34048

In this paper we investigate the fluctuations of solar activity and their links with climatic parameters in West Africa. We achieve our research by investigating several data plotted using averages. Mean to our results we can assume that active solar is associated with weak incident cosmic ray consequently with low cloudiness which brings warming. Likewise, quiet solar is associated with important cloud cover and consequently brings important precipitations and chills terrestrial atmosphere. This implies the necessity to deal with space phenomenon by considering the severe interconnection between solar activity indices for interplanetary and earth environment weather forecasting.

Modeling the Ionosphere during Quiet Time Variation at Ouagadougou in West Africa  [PDF]
Emmanuel Nanema, Doua Allain Gnabahou, Christian Zoundi, Frédéric Ouattara
International Journal of Astronomy and Astrophysics (IJAA) , 2018, DOI: 10.4236/ijaa.2018.82011
Abstract: Ionosphere parameters determination is used to characterize its composition in particles. These results have been compared to data curried from Ouagadougou station. The present study deals with Total Electron Contents (TEC) results determined by Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) version 1.94 and International Reference Ionosphere (IRI) version 2012 during solar cycle 22. The minimum and maximum phases of solar cycle 22 are considered in this study for TEC determination. The station is located at Ouagadougou, in western Africa, characterized by its latitude (12.4°N) and longitude (358.5°E). The present study completes the two previous articles on hmF2 and foF2 parameters determination on the same station by comparison between TEC results carried out from TIEGCM and IRI models. So that, quiet time condition is determined by Aa (≤20 nT) for the five quietest days in each characteristic month of seasons. Rz values characterize minimum and maximum solar cycle phases.
Electron Bulk Surface Density Effect on Critical Frequency in the F2-Layer  [PDF]
Emmanuel Nanéma, Issaka Ouédraogo, Christian Zoundi, Frédéric Ouattara
International Journal of Geosciences (IJG) , 2018, DOI: 10.4236/ijg.2018.99033
Abstract: Ionosphere layer is the atmosphere region which reflects radio waves for telecommunication. The density in particles in this layer influences the quality of communication. This study deals with the effects of Total Electron Contents (TEC) on the critical frequency of radio waves in the F2-layer. Total Electron Contents parameter symbolizes electron bulk surface density in ionosphere layer. Above critical frequency value in F2 layer (foF2), radio waves pass through ionosphere. The knowledge of this value enables to calibrate transmission frequencies. In this study, we consider TEC effects on foF2 under quiet time conditions during the maximum and the minimum of solar cycle 22, at Ouagadougou station, in West Africa. The study also considers the effects of seasons and the hourly variability of TEC and foF2. This work shows winter anomaly on foF2 and TEC on minimum and maximum of solar cycle phase respectively. Running International Reference Ionosphere (IRI) model enables to carry out the effects of TEC on foF2 by use of their monthly average values. This leads to a new approach to calibrate radio transmitters.
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  [PDF]
Ali Mahamat Nour, Ouattara Frédéric, Zerbo Jean Louis, Gyébré Aristide Marie Frédéric, Nanéma Emmanuel, Zougmoré Fran?ois
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.63014
Abstract: The statistical study of F2 layer critical frequency at Dakar station from 1971 to 1996 is carried out. This paper shows foF2 statistical diurnal for all geomagnetic activities and all seasons and that during solar maximum and minimum phases. It emerges that foF2 diurnal variation graphs at Dakar station exhibits the different types of foF2 profiles in African EIA regions. The type of profile depends on solar activity, season and solar phase. During solar minimum and under quiet time condition, data showthe signature of a strength electrojet that is coupled with intense counter electrojet in the afternoon. Under disturbed conditions,mean intense electrojet is observed in winterduring fluctuating and recurrent activities. Intense counter electrojet is seen under fluctuating and shock activities in all seasons coupled with strength electrojet in autumn. In summerand spring under all geomagnetic activity condition, there is intense counter electrojet. During solar maximum, in summer and spring there is no electrojet under geomagnetic activity conditions.Winter shows a mean intense electrojet. Winter and autumn are marked by the signature of the reversal electric field.
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