Equatorial vertical E×B drift velocities inferred from ionosonde measurements over Ouagadougou and the IRI-2007 vertical ion drift model

Oyekola, O. S.; Kolawole, L. B.

doi:10.1016/j.asr.2010.04.003

Cited by 17 publications

(4 citation statements)

References 40 publications

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“…These results highlight the fact that the elevated F region around midnight does lead to the development of postmidnight EFIs over Jicamarca. From the hourly averaged h m F 2 values obtained from Ouagadougou in Africa, Oyekola and Kolawole [2010] investigated the vertical E × B drifts during solar maximum year 1989, an evening PRE peak was found located around 1900 LT during the June solstice. The usual evening PRE in the vertical drift, which is a manifestation of the enhancement of eastward electric field, peaks around 1800 LT and reverses to westward by 1900 LT over Jicamarca [e.g., Fejer et al , 1999].…”

Section: Discussionmentioning

confidence: 99%

On the occurrence of postmidnight equatorialFregion irregularities during the June solstice

Ning

Abdu

et al. 2011

J. Geophys. Res.

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[1] Postmidnight equatorial F region irregularities (EFIs) are known to develop mainly during the solstitial months. However, it is not well understood whether they occur at all longitudes and what process causes their occurrence at different longitude sectors. In this study, we use the GPS total electron content (TEC) fluctuations obtained from a global GPS network and spread F in ionograms from Jicamarca (283°E, 12°S, Dip 1°N) in the American longitude sector and Kwajalein (167°E, 9°N, Dip 4°N), Bac Lieu (106°E, 9°N, Dip 2°N), and Chumphon (99°E, 11°N, Dip 3°N) in the Pacific and Asian longitude sectors during 2000-2009, to investigate the EFI characteristics during June solstice. Results from global TEC fluctuations show that at solar maximum, the occurrence rate of postmidnight EFIs is high in African and Pacific regions, moderate in the Southeast Asian region, and low in the Peruvian region and that most postmidnight EFIs are the continuation of postsunset EFIs. During solar minimum the postmidnight EFIs were rarely observed in TEC but were very frequent in ionograms. The latter had more frequent postmidnight onsets over Peru, whereas they were initiated during late postsunset hours in Pacific and Southeast Asian longitudes. In both longitudes the postsunset layer rise occurred with some delay. The layer rise was more prominent on spread F nights over Jicamarca and less so over Pacific longitudes. The results showing different degrees of association at the different longitudes between the postsunset/postmidnight EFIs and F layer heights highlight the influence of other factors in the late-night EFI development. Perturbation seeds and plasma drifts/neutral winds, in particular, are discussed as strong candidates for causing these irregularities in the June solstitial months of solar minimum years.

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Section: Discussionmentioning

confidence: 99%

On the occurrence of postmidnight equatorialFregion irregularities during the June solstice

Ning

Abdu

et al. 2011

J. Geophys. Res.

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“…Observations of vertical plasma drifts in the equatorial region of the African ionosphere have also been inferred from ionosonde observations mostly during nighttime solar maximum magnetospherically quiet conditions (e.g., Oluwafemi, 2007, 2008;Oyekola, 2009a, b;Oyekola and Kolawole, 2010). By and large, except for magnitude the characteristic features of equatorial electromagnetic drifts in the African ionosphere are in good agreement with those obtained for the equatorial region in the America sector using ISR observations (e.g., Fejer et al, 1979Fejer et al, , 1991.…”

Section: Introductionmentioning

confidence: 99%

Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

Oyekola¹

2012

Earth Planet Sp

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In this paper, hourly median value of ionosonde measurements: peak height F 2 -layer (h m F 2 ), F 2 -layer critical frequency ( f o F 2 ) and propagation factor M(3000)F 2 made at near-equatorial dip latitude, Ouagadougou, Burkina Faso (12• N, 1.5 • W; dip: 1.5• N) and relevant F 2 -layer parameters: thickness parameter (B o ), electron temperature (T e ), ion temperature (T i ), total electron content (TEC) and electron density (N e ) (at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial electrodynamics on the diurnal structure of F 2 -layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. It is demonstrated that the month-by-month morphological patterns between vertical E × B drifts and F 2 -layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F 2 -layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-B o , IRI-T e and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Examination of the association between measured f o F 2 , h m F 2 and M(3000)F 2 illustrates consistent much more smaller correlation coefficients with no systematic linkage.

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“…Although the Fejer-Scherliess drift model was developed for measurements at Jicamarca, we have extended the model to all longitudes since it is used as the vertical ion drift component of the IRI model (Fejer et al, 1999;Bilitza, 2018). However, previous work has compared vertical E Â B drifts in other longitude zones to the drifts in the Fejer-Scherliess drift model and found multiple differences between the vertical drift behavior of the model and observations (e.g., Oyekola & Kolawole, 2010;Saranya et al, 2014;Yizengaw et al, 2014;Dubazane et al, 2018). So although we expect there to be differences between the Fejer-Scherliess model drifts and the C/NOFS drifts, the key finding is the consistency between the C/NOFS drifts and the bubble occurrence frequency.…”

Section: Comparison To Fejer-scherliessmentioning

confidence: 99%

Growin: Modeling ionospheric instability growth rates

Smith

Klenzing²

2022

J. Space Weather Space Clim.

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Seasonal and zonal climatologies of Rayleigh-Taylor growth rates under geomagnetically quiet conditions during solar minimum and solar moderate conditions as a function of local time and altitude are calculated using open source data and software. It is under the action of the Rayleigh-Taylor instability that plumes of depleted plasma, or plasma bubbles, are understood to develop in the bottomside of the equatorial ionosphere. The growin python module utilizes other Heliophysics python modules to collate and process vertical plasma drift to drive the SAMI2 is Another Model of the Ionosphere (SAMI2) model and subsequently calculate the flux tube integrated Rayleigh-Taylor growth rate. The process is repeated for two different types of drift inputs: the Fejer-Scherliess model and measured drifts from the Communication/Navigation Outage Forecasting System (C/NOFS). These growth rates are compared to bubble occurrence frequencies obtained from a dataset of bubbles detected by the C/NOFS satellite. There is agreement between periods of strong positive instability growth and high frequencies of bubble occurrence in both low and moderate solar activity conditions when using C/NOFS drifts. Fejer-Scherliess drifts are only in agreement with bubble occurrence frequencies during moderate solar activity conditions. Bubble occurrence frequencies are often above 25% even when growth rates in the bottomside F region are negative. The climatological nature of the growth rates discussed here begs further study into the day-to-day variability of the growth rate and its drivers.

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Equatorial vertical E×B drift velocities inferred from ionosonde measurements over Ouagadougou and the IRI-2007 vertical ion drift model

Cited by 17 publications

References 40 publications

On the occurrence of postmidnight equatorialFregion irregularities during the June solstice

On the occurrence of postmidnight equatorialFregion irregularities during the June solstice

Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

Growin: Modeling ionospheric instability growth rates

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