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Statistical Investigation of the relationship between the occurrences of AGW, ESF and ESF types in the American sector
  • Emmanuel Olagunju,
  • Olayinka Olawepo,
  • Victoria Ajani
Emmanuel Olagunju
University of Ilorin

Corresponding Author:[email protected]

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Olayinka Olawepo
University of Ilorin
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Victoria Ajani
University of Ilorin
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Abstract

Equatorial Spread F (ESF), a manifestation of nighttime irregularities in the equatorial ionosphere has been linked to Atmospheric Gravity Waves (AGW) by different authors. However, there have not been much study to ascertain the extent of the relationship between the occurrence of AGW and the generation and occurrence of ESF. This study investigates the correlation between AGW and ESF occurrences during the year 2016, using data obtained with the aid of satellite borne Atmospheric Infrared Sounder (AIRS) and ionogram obtained with the aid of Digisonde Portable Sounder (DPS-4) located at Jicamarca, (geog. Lat. 11.95, Long. 76.87 and geomagnetic Lat. 9.28, Long.-7.92), an equatorial station in the Peruvian sector. During this period, 72.9% of AGW occurrence was observed between 18:00UT and 00:00UT (post-sunset period) while the remaining 27.1% occurrence was observed between 00:00 and 04:00UT (post-midnight period) coinciding with the period of occurrence of ESF. Results from the study reveal that the occurrences of ESF and AGW are independent of each other. An insignificant correlation (0.39) was found between the days of occurrence of the two phenomena. While ESF occurrence is a regular daily occurrence with local time dependence, AGW propagation is not dependent on local time. For Jicamarca, we found that ESF occurrence is greater during the solstice months than equinox. The probability of AGW reaching the bottomside F-layer depends on the properties of the wave. In this study, AGW was able to penetrate ionospheric heights on only six occasions. The results also show that AGW occurrence can only influence the conditions that trigger ESF rather than triggering ESF altogether. The occurrence of AGW tends to influence the occurrence of MSF type of ESF which is predominantly a post sunset phenomenon in preference to the other two types. Coefficient of correlation between AGW and MSF ranged between