Statistical characterisation of spread F over South Africa

Amabayo, Emirant B.; McKinnell, Lee-Anne; Cilliers, Pierre J.

doi:10.1016/j.asr.2011.08.029

Cited by 12 publications

(9 citation statements)

References 28 publications

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“…Our observations in solar activity variation at CMU, CPN and KTB show that the percentage of RSF occurrence increases with the level of solar activity, while the percentages of FSF occurrence, on the contrary, decreases with the level of solar activity. The spread-F observation as the solar activity varies at Grahamstown (33.32°S, 26.50°E) and Madimbo (22.38°S, 30.88°E), South Africa from 2001(Amabayo et al, 2011 shows that the MSF and FSF are the dominant types at these two stations and the probability of both types increases as the level of solar activity decreases, similarly to what this paper has shown for the FSF occurrence. These authors found also that the occurrence percentages of MSF and FSF are higher at Grahamstown than at Madimbo, and they attributed this fact both to the differences in the level of atmospheric GWs in the ionospheric mid-latitude F-region and to the latitudinal difference between these two stations.…”

Section: Resultssupporting

confidence: 86%

“…For instance, the issues in the equatorial ionosphere-thermosphere electrodynamics over American and Southeast Asia sectors (Abdu, 2001;Cabrera et al, 2010;Candido et al, 2011;Maruyama et al, 2007) or the investigations to find out the relation between the spread-F occurrence and the sporadic-E (Es) characteristics over the Brazilian conjugate point equatorial experiment (COPEX) (Batista et al, 2008). The statistics of spread-F occurrence over different regions confirm that at the different geomagnetic declinations, latitudinal and longitudinal regions, ESF occurrence and intensity have distinct annual or seasonal patterns (Abdu et al, 1981;Maruyama and Matuura, 1984;Sastri, 1999;Maruyama et al, 2002Maruyama et al, , 2007Saito and Maruyama, 2007;Wang et al, 2008Wang et al, , 2010Hoang et al, 2010;Amabayo et al, 2011;Pezzopane et al, 2013).…”

Section: Introductionmentioning

confidence: 68%

“…Besides, the variations of ESF were investigated as a function of geophysical indices such as the estimated planetary K-index (Kp), the disturbance storm time index (Dst), which indicate the level of magnetic activity or the geomagnetic storm, or the sunspot number (SSN), the F10.7 index, which indicate the level of solar activity. The characteristics and the occurrence rates of each ESF type differ according to the different levels of solar activity and seasonal variation (Abdu et al, 1998;Wang et al, 2008Wang et al, , 2010Amabayo et al, 2011). The spread-F occurrences are continuously investigated in various regions to ascertain the hypothesis of ESF characteristics and occurrences.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The occurrence of equatorial spread-F at conjugate stations in Southeast Asia

Klinngam

Supnithi

Rungraengwajiake

et al. 2015

Advances in Space Research

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The occurrence of equatorial spread-F at conjugate stations in Southeast Asia

Klinngam

Supnithi

Rungraengwajiake

et al. 2015

Advances in Space Research

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“…The seasonal variability of nighttime midlatitude spread F has been reported by several authors (Singleton, 1968;Bowman, 1998;Bhaneja et al, 2009;Deminov et al, 2009;Amabayo et al, 2011). Singleton (1968) suggested that FSF occurrence maximizes around 40°to 50°in latitude, whereas RSF dominates between 45°to 55°.…”

Section: Discussionmentioning

confidence: 60%

Multi-station investigation of spread F over Europe during low to high solar activity

Paul

Haralambous

Oikonomou

et al. 2018

J. Space Weather Space Clim.

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Spread F is an ionospheric phenomenon which has been reported and analyzed extensively over equatorial regions on the basis of the Rayleigh-Taylor (R-T) instability. It has also been investigated over midlatitude regions, mostly over the Southern Hemisphere with its generation attributed to the Perkins instability mechanism. Over midlatitudes it has also been correlated with geomagnetic storms through the excitation of travelling ionospheric disturbances (TIDs) and subsequent F region uplifts. The present study deals with the occurrence rate of nighttime spread F events and their diurnal, seasonal and solar cycle variation observed over three stations in the European longitude sector namely Nicosia (geographic Lat: 35.29 °N, Long: 33.38 °E geographic: geomagnetic Lat: 29.38 °N), Athens (geographic Lat: 37.98 °N, Long: 23.73 °E geographic: geomagnetic Lat: 34.61 °N) and Pruhonice (geographic Lat: 50.05 °N, Long: 14.41 °E geographic: geomagnetic Lat: 47.7 °N) during 2009, 2015 and 2016 encompassing periods of low, medium and high solar activity, respectively. The latitudinal and longitudinal variation of spread F occurrence was examined by considering different instability triggering mechanisms and precursors which past literature identified as critical to the generation of spread F events. The main findings of this investigation is an inverse solar cycle and annual temporal dependence of the spread F occurrence rate and a different dominant spread F type between low and high European midlatitudes.

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“…This conclusion is consistent with the statistical characterization of spread F over South Africa made by Amabayo et al . [].…”

Section: Filtering the Observations And Model Resultsmentioning

confidence: 99%

Assimilation procedures for updating ionospheric profiles below the F2 peak

et al. 2013

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[1] This paper describes and compares two real-time assimilative ionospheric models, with an emphasis on their ability to provide accurate profiles of the electron density below the peak of the F2 layer at a midlatitude location, given automatically processed vertical incidence ionograms at a single location. The two models are specifically oriented toward several important practical applications of high-frequency (HF) radio propagation: HF communications, single station location of HF transmitters, and coordinate registration for OTHR. Both models start with the International Reference Ionosphere (IRI) as a background ionosphere and assimilate digisonde observations (either the ionogram or the profile) and available GPS total electron content observations. The digisonde data from one site in the Republic of South Africa (RSA) provide the ionosonde assimilation data, while the other three digisondes in the RSA provide the ground-truth observations of foF2, hmF2, and the plasma frequency profile. Since the four RSA digisondes receive each other's transmissions, maximum observed frequencies have also been used as ground truth. The models tested have both been found to provide significant improvements over the IRI and to have similar accuracies for the study interval (September 2011). The errors of the models are very close to the minimum achievable errors for all the validation parameters, which seem to be set by the ubiquitous traveling ionospheric disturbances being different at the different locations. For the optimum ground-truth location~685 km from the digisonde providing the assimilation data, the RMS errors in foF2 were found to be 0.2 MHz (night) and 0.5 MHz (day).

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Statistical characterisation of spread F over South Africa

Cited by 12 publications

References 28 publications

The occurrence of equatorial spread-F at conjugate stations in Southeast Asia

The occurrence of equatorial spread-F at conjugate stations in Southeast Asia

Multi-station investigation of spread F over Europe during low to high solar activity

Assimilation procedures for updating ionospheric profiles below the F2 peak

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