West African equatorial ionospheric parameters climatology based on Ouagadougou ionosonde station data from June 1966 to February 1998

Ouattara, Frédéric; Amory‐Mazaudier, Christine; Fleury, Rolland; Duchesne, Patrick Lassudrie; Vila, P.; Petitdidier, Monique

doi:10.5194/angeo-27-2503-2009

Cited by 34 publications

(34 citation statements)

References 28 publications

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“…During sunrise, the magnetic flux tubes again filled up because of their small volume, resulting in a sudden increase in ionization due to increasing thermospheric temperatures during sunrise (Oron et al, 2013). The observed nighttime GPS TEC enhancement could be attributed to the tidal winds, which blow the ionization across the geomagnetic field.…”

Section: Hourly Variation In Gps Tec Across Longitudesmentioning

confidence: 93%

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

et al. 2017

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Abstract. The study of diurnal and seasonal variations in total electron content (TEC) over Nigeria has been prompted by the recent increase in the number of GPS continuously operating reference stations (CORSs) across Nigeria as well as the reduced costs of microcomputing. The GPS data engaged in this study were recorded in the year 2012 at nine stations in Nigeria located between geomagnetic latitudes -4.33 and 0.72 • N. The GPS data were used to derive GPS TEC, which was analysed for diurnal and seasonal variations. The results obtained were used to produce local GPS TEC maps and bar charts. The derived GPS TEC across all the stations demonstrates consistent minimum diurnal variations during the pre-sunrise hours 04:00 to 06:00 LT, increases with sharp gradient during the sunrise period (∼ 07:00 to 09:00 LT), attains postnoon maximum at about 14:00 LT, and then falls to a minimum just before sunset. Generally, daytime variations are found to be greater than nighttime variations, which range between 0 and 5 TECU. The seasonal variation depicts a semi-annual distribution with higher values (∼ 25-30 TECU) around equinoxes and lower values (∼ 20-25 TECU) around solstices. The December Solstice magnitude is slightly higher than the June Solstice magnitude at all stations, while March Equinox magnitude is also slightly higher than September Equinox magnitude at all stations. Thus, the seasonal variation shows an asymmetry in equinoxes and solstices, with the month of October displaying the highest values of GPS TEC across the latitudes.

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Section: Hourly Variation In Gps Tec Across Longitudesmentioning

confidence: 93%

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

et al. 2017

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“…This is related to winter maximum of O atoms, implying the relative increase of light gases above the winter hemisphere (Scialom, 1974), due to dynamic influences in the thermosphere (Rishbeth and Müller-Wodarg, 2006). Ouattara et al (2009) propose to explain the absence of the winter anomaly during cycle 20 by the influence of fluctuating wind stream activity.…”

Section: Annual and Semiannual Variationsmentioning

confidence: 99%

“…The difference in the correlation coefficients from one sunspot cycle to another can be explained by changes in the solar cycle intensity (Balan et al, 1993). Ouattara et al (2009) found for Ouagadougou, located at the magnetic equator in the Northern Hemisphere, a good correlation between the sunspot number and foF2, foF1, and h F1, but no correlation for foE, h F2 and h E. The absence of correlation between the sunspot number and foE at the equator can be explained by the existence of the equatorial electrojet, which drives instabilities and generates strong plasma waves which strongly affect the electron density (Farley, 2009). …”

Section: Solar Cycle Variationsmentioning

confidence: 99%

“…We use hourly values at full hours of critical frequencies foF2, foF1, foE and foEs and virtual heights h F2, h F1, h E, h Es. The ionosonde data were continuously recorded by three different ionospheric vertical sounders: the IRX-Hungarian (1962-1966, the AIC-Russian (1967-1994, the IPS71-Australian (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002).…”

Section: Data Set and Data Analysismentioning

confidence: 99%

“…-The long term variations observed by ionosonde located in different regions were previously analyzed by Elias and Ortiz de Adler (2006), Bremer (2008) and Ouattara et al (2009). Three factors were proposed to explain the long term variation (Lastovicka et al, 2006;Elias, 2009): (1) green house gases (Bremer, 2008), (2) changes in the Earth's magnetic field (Elias and Ortiz de Adler, 2006;Cnossen and Richmond, 2008) and (3) geomagnetic activity.…”

Section: Introductionmentioning

confidence: 99%

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Time variations of the ionosphere at the northern tropical crest of ionization at Phu Thuy, Vietnam

Thu

Amory‐Mazaudier²

2011

Ann. Geophys.

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Abstract. This study is the first which gives the climatology of the ionosphere at the northern tropical crest of ionization in the Asian sector. We use the data from Phu Thuy station, in Vietnam, through three solar cycles (20, 21 and 22), showing the complete morphology of ionosphere parameters by analyzing long term variation, solar cycle variation and geomagnetic activity effects, seasonal evolution and diurnal development. Ionospheric critical frequencies, foF2, foF1 and foE, evolve according to the 11-year sunspot cycle. Seasonal variations show that foF2 exhibits a semiannual pattern with maxima at equinox, and winter and equinoctial anomalies depending on the phases of the sunspot solar cycle. foF2 exhibits a semiannual variation during the minimum phase of the sunspot solar cycle 20 and the increasing and decreasing phases of solar cycle 20, 21 and 22. foF1 exhibits an annual variation during the maximum phase of solar cycles 20, 21 and 22. h F2 shows a regular seasonal variation for the different solar cycles while h F1 exhibits a large magnitude dispersion from one sunspot cycle to another. The long term variations consist in an increase of 1.0 MHz for foF2 and of 0.36 MHz for foF1. foE increases 0.53 MHz from solar cycle 20 to solar cycle 21 and then decreases −0.23 MHz during the decreasing phase of cycle 21. The diurnal variation of the critical frequency foF2 shows minima at 05:00 LT and maxima around 14:00 LT. foF1 and foE have a maximum around noon. The diurnal variation of h F2 exhibits a maximum around noon. The main features of h F1 are a minimum near noon and the maximum near midnight. Other

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Solar cycle, seasonal, and diurnal variations of subauroral ion drifts: Statistical results

2014

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The solar cycle, seasonal, and diurnal variations of the subauroral ion drifts (SAIDs) are investigated for the first time to use such a large database of 18,226 SAID events observed by the DMSP satellites during 1987-2012. Statistical results show that SAIDs occur mostly at 60.1°invariant latitude and 2230 magnetic local time with a typical half width of 0.57°, move equatorward during high solar activities with large widths, and have two occurrence peaks in spring and fall equinoxes and two valleys in summer and winter solstices. The seasonal variation of SAID latitude has two valleys in spring and fall, and SAID width has a valley distribution with a minimum in summer. SAIDs exhibit a clear day-to-night difference in latitude. The diurnal variation of SAID width has a morning valley and an afternoon peak. The generation mechanism of SAID associated with the electron precipitation and the downward field-aligned current is also supported in this study.

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West African equatorial ionospheric parameters climatology based on Ouagadougou ionosonde station data from June 1966 to February 1998

Cited by 34 publications

References 28 publications

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

Time variations of the ionosphere at the northern tropical crest of ionization at Phu Thuy, Vietnam

Solar cycle, seasonal, and diurnal variations of subauroral ion drifts: Statistical results

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