Variability of foF2 in the African equatorial ionosphere

Akala, A. O.; Oyeyemi, E. O.; Somoye, E.O.; Adeloye, A. B.; Adewale, A.O.

doi:10.1016/j.asr.2010.01.003

Cited by 36 publications

(36 citation statements)

References 15 publications

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“…2(a-c) shows the plots of monthly hourly median for 2009 until 2011. Bilitza et al (2004), Akala et al (2010) and Pietrella et al (2012) discovered that variability of foF2/NmF2, MUF and h'F2 are characterized by pre-sunrise and post-sunset peaks; this is due to the steep electron density gradients occasioned by the onset and turn-off of solar ionisation. From Fig.…”

Section: Resultsmentioning

confidence: 98%

Comparison of maximum usable frequency (MUF) variability over Peninsular Malaysia with IRI model during the rise of solar cycle 24

Malik

Abdullah

et al. 2016

Journal of Atmospheric and Solar-Terrestrial Physics

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Section: Resultsmentioning

confidence: 98%

Comparison of maximum usable frequency (MUF) variability over Peninsular Malaysia with IRI model during the rise of solar cycle 24

Malik

Abdullah

et al. 2016

Journal of Atmospheric and Solar-Terrestrial Physics

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“…The equatorial and low-latitude ionosphere manifests a number of unique phenomena, such as the equatorial electrojet (EEJ), equatorial spread F (ESF), equatorial plasma bubble (EPB), and equatorial ionization anomaly (EIA) among others, and is characterized by large transient variations (Bagiya et al, 2009;Mukherjee et al, 2010;Chauhan et al, 2011;Bolaji et al, 2012). The equatorial ionosphere is highly dynamic and consequently poses serious threats to communication and navigation systems (Akala et al, 2010(Akala et al, , 2011(Akala et al, , 2012.…”

Section: Introductionmentioning

confidence: 99%

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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“…Even in the early days of ionospheric research, it was noticed that geomagnetic activity is accompanied or quickly followed by marked changes in the F2-layer. The response of the ionospheric foF2 over equatorial region to storms events, during the night-time and post-midnight hours indicates negative responses of the ionospheric foF2, while that of the daytime hours indicates positive responses (Akala et al 2010). The ionosphere over equatorial latitudes is highly dynamic, and consequently poses serious threats to communication and navigation systems, especially during magnetically disturbed (geomagnetic storm) days (Kumar and Gwal 2000;Basu et al 2002).…”

Section: Introductionmentioning

confidence: 98%

“…Conventionally, the strength of a geomagnetic storm is represented by geomagnetic indices (the disturbance storm time (Dst), planetary K (Kp) index, etc.) (Akala et al 2010). It is possible to measure the strength of a geomagnetic storm by the Dst, because the strength of the surface magnetic field at low latitudes is inversely proportional to the energy content of the ring current, which increases during geomagnetic storms (Ratcliffe 1972).…”

Section: Introductionmentioning

confidence: 99%

On the effects of geomagnetic storms and pre storm phenomena on low and middle latitude ionospheric F2

Adekoya

Chukwuma

Bakare

et al. 2012

Astrophys Space Sci

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This paper presents some features of the ionospheric response observed in equatorial and mid-latitudes region to two strong geomagnetic storms, occurring during Oct. 19-23, 2001 and May 13-17, 2005 and to understand the phenomena of pre-storm that lead to very intense geomagnetic storms. The result point to the fact that pre-storm phenomena that leads to intense ionospheric storm are; large southward turning of interplanetary magnetic field Bz, high electric field, increase in flow speed stream, increase in proton number density, high pressure ram and high plasma beta. The magnitude of Bz turning into southward direction from northward highly depends upon the severity of the storm and the variation in F2 layer parameter at the time of geomagnetic storm are strongly dependent upon the storm intensity. A detailed analysis of the responses of the ionosphere shows that during the storm periods, foF2 values depleted simultaneously both in the equatorial and mid latitude. Observation also shows that low to moderate variations in ionospheric F2 at the pre-storm period may signal the upcoming of large ionospheric disturbances at the main phase. The ionospheric F2response for low and mid latitude does not show any significant differences during the storm main phase and the prestorm period. The ionospheric response during the pre-storm period is thought very puzzling. The period is observed to be depleted throughout with low-moderate effect across all the stations in the low and mid latitude.

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Variability of foF2 in the African equatorial ionosphere

Cited by 36 publications

References 15 publications

Comparison of maximum usable frequency (MUF) variability over Peninsular Malaysia with IRI model during the rise of solar cycle 24

Comparison of maximum usable frequency (MUF) variability over Peninsular Malaysia with IRI model during the rise of solar cycle 24

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

On the effects of geomagnetic storms and pre storm phenomena on low and middle latitude ionospheric F2

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