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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/angeo-2019-24
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-2019-24
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 27 Feb 2019

Regular paper | 27 Feb 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Annales Geophysicae (ANGEO).

Spread F occurrence features at different longitudinal regions during low and moderate solar activity

Abimbola O. Afolayan1, Singh J. Mandeep1,2, Mardina Abdullah1,2, Suhaila M. Buhari2,3, Tatsuhiro Yokoyama4, and Pornchai Supnithi5 Abimbola O. Afolayan et al.
  • 1Center of Advanced Electronic and Communication Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
  • 2Space Science Centre (ANGKASA), Institute of Climate Change, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
  • 3Geomatic Innovation Research Group, Faculty of Science, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia
  • 4Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan
  • 5Faculty of Engineering King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand

Abstract. A comparative study of the equatorial spread F occurrence was conducted at different longitudes during 2009 or 2010 and 2011 or 2013 which represents the low (LSA) and moderate (MSA) solar activity periods respectively. The ionogram data were recorded at low latitude stations including Jicamarca (JIC; 75.76° W, 8.17° S), Peru; Fortaleza (FZA; 38.52° W, 3.73° S), Brazil; Ilorin (ILR; 7.55° E, 9.93° N), Nigeria; Chumphon (CPN; 88.46° E, 11° N), Thailand and Kwajalein (KWA; 167.73° E, 8.72° N), Marshal Island. The range type spread F (RSF) occurrence was manually recorded at an hour interval between 18:00–06:00 LT and a monthly average of the RSF occurrence was estimated for each of the seasons. The observed features of the RSF occurrence and its longitudinal distribution at different seasons include the difference in the onset time, duration and peak of occurrence. The significant observations include the asymmetric RSF occurrence distribution during the equinoctial season at most of the longitudes, while during the solstice seasons there are cases of discrepancy in the RSF occurrence with respect to the sunset terminator-magnetic field alignment. The inconsistent pattern of the RSF occurrence percentage and the post-sunset rise of the F layer in relation to the sunset time lag were analyzed. While the possible role of the seed perturbation effect was discussed with respect to some of the peculiar features observed in the longitudinal/seasonal distribution of the spread F occurrence percentage.

Abimbola O. Afolayan et al.
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Short summary
The equatorial spread F (ESF) is a nighttime phenomenon which has the potential to have a deleterious effect on the radio communication system. We investigated the parameters influencing the seasonal morphology of the ESF using the ionosonde data taken at different longitudinal sectors. The ESF occurrence features including the onset time and seasonal asymmetry showed distinct patterns across these sectors. The gravity wave was identified as a significant factor to these seasonal distributions.
The equatorial spread F (ESF) is a nighttime phenomenon which has the potential to have a...
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