Seasonal and solar cycle variability in <i>F</i>‐region vertical plasma drifts over Ouagadougou

Oyekola, O. S.; Ojo, Akin; Akinrimisi, J.; Depaula, E. R.

doi:10.1029/2007ja012560

Cited by 16 publications

(12 citation statements)

References 53 publications

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“…Using h m F 2 method, Oyekola et al . [] have also studied the vertical drifts over African region by using ionosonde. They showed that their PRE drift variations are in good agreement with solar flux variations.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of the equatorial plasma drifts as obtained by using Canadian Doppler ionosonde over southern tip of India

et al. 2016

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We present here characteristics of the Doppler drift measurements over Tirunelveli (8.73°N, 77.70°E; dip 0.5°N), an equatorial site over Southern India using Doppler interferometry technique of Canadian ionosonde. Three‐dimensional bulk motions of the scatterers as reflected from the ionosphere are derived by using Doppler interferometry technique at selected frequencies using spaced receivers arranged in magnetic E‐W and N‐S directions. After having compared with Lowell's digisonde drifts at Trivandrum, we studied the temporal and seasonal variabilities of quiet time drifts for the year 2012. The observations showed higher vertical drifts during post sunset in the equinox followed by winter and summer seasons. The comparison of Doppler vertical drifts with the drifts obtained from (a) virtual height and (b) Fejer drift model suggests that Doppler vertical drifts are relatively higher as compared to the drifts obtained from model and virtual height methods. Further, it is seen that vertical drifts exhibited equinoctial asymmetry in prereversal enhancement quite similar to such asymmetry observed in the spread F in the ionograms and GPS L band scintillations. The zonal drifts, on the other hand, showed westward during daytime with mean drifts of ~150–200 m/s and correlated well with equatorial electrojet strength indicating the role of E region dynamo during daytime, while they are eastward during nighttime with mean drifts of ~100 m/s resembling F region dynamo process. Also, zonal drifts showed large westward prior to the spread F onset during autumn equinox than vernal equinox, suggesting strong zonal shears which might cause equinoctial asymmetry in spread F.

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Section: Discussionmentioning

confidence: 99%

Characteristics of the equatorial plasma drifts as obtained by using Canadian Doppler ionosonde over southern tip of India

et al. 2016

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“…A likely cause of substantial variability of F region vertical ion drifts may perhaps are due to the trans‐equatorial wind intensity effects since the two stations (Ibadan and Ouagadougou) are not located exactly at the dip equator. A number of theoretical, model calculations, and observational evidence have shown that transequatorial magnetic meridional wind intensity play a critical role in the variability of ion drifts, especially near the prereversal hours [e.g., Maruyama , 1988; Mendillo et al , 1992; Abdu et al , 2006; Su et al , 2007; Oyekola et al , 2007]. Moreover, Mendillo et al [2002] showed that the F 2 layer variability appears to be related more to variations in winds than to variations of thermospheric composition.…”

Section: Discussionmentioning

confidence: 99%

Solar and geomagnetic trends of equatorial evening and nighttime F region vertical ion drifts

Oyekola

Oluwafemi

2008

J. Geophys. Res.

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“…Thus in the post sunset hours F layer moves upward rapidly and then comes down due to decay of this PRE associated eastward electric field. It is noticed that PRE varies considerably from day‐to‐day and it also depends on season, solar flux and longitude [ Abdu et al , 1981; Batista et al , 1986; Hari and Krishna Murthy , 1995; Fejer and Scherliess , 2001; Oyekola et al , 2007]. As a result the post sunset height of F layer varies considerably from day to day for magnetically quiet periods, which gets reflected in the monthly quiet time pattern of apparent base height of F layer h ′ F .…”

Section: Data Used and Quantitative Estimate Of Magnetic Activitymentioning

confidence: 99%

Study of disturbance dynamo effects at nighttime equatorial F region in Indian longitude

2011

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[1] Post sunset height of F layer may significantly increase or decrease as compared to their monthly quiet time pattern due to superimposed disturbed time electric field associated with either disturbance dynamo (DD) or prompt penetration (PP) or combination of both DD and PP. In this paper, the effects associated with disturbed time eastward electric field causing upward movement of F layer in the post sunset hours are investigated. Ionosonde data recorded at dip equatorial station Trivandrum for the period of 1990-2003 are scaled to obtain the variation of h′F from 17-31LT. Effect of magnetic activity on h′F (DH) is obtained by subtracting monthly quiet time average of h′F from disturbed time h′F. The maximum enhancement seen in h′F i.e DH max provides the quantitative estimate of maximum effect of magnetic activity at equatorial F region. Here 97 magnetically disturbed days with DH max ≥ 80 km are studied. Geomagnetic activity index ap is used along with AE and attempt has been made to identify the effects associated with short and long term DD electric field. It is found that the duration of short and long term DD effects seen at equatorial F region decreases with increase in solar flux. However this dependence is not applicable close to early morning hours (≥ 05LT). Time delays required to produce maximum effect at equatorial F region during high solar flux are found to be 16-23 hrs (0.5-4 hrs) for long (short) term DD effects studied here.

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Seasonal and solar cycle variability in F‐region vertical plasma drifts over Ouagadougou

Cited by 16 publications

References 53 publications

Characteristics of the equatorial plasma drifts as obtained by using Canadian Doppler ionosonde over southern tip of India

Characteristics of the equatorial plasma drifts as obtained by using Canadian Doppler ionosonde over southern tip of India

Solar and geomagnetic trends of equatorial evening and nighttime F region vertical ion drifts

Study of disturbance dynamo effects at nighttime equatorial F region in Indian longitude

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