The Role of Meridional Neutral Winds On The Occurrence of Post-Sunset Equatorial Ionospheric Irregularities

Aderaw, Bantayehu

dc.contributor.author	Aderaw, Bantayehu
dc.date.accessioned	2024-11-20T07:38:12Z
dc.date.available	2024-11-20T07:38:12Z
dc.date.issued	2024-11
dc.identifier.uri	http://ir.bdu.edu.et/handle/123456789/16225
dc.description.abstract	Ground- and satellite-based radio communication and navigation systems are greatly impacted by the post-sunset equatorial ionospheric irregularities that exist in the Earth's ionosphere. Although post-sunset vertically upward plasma drift velocity and zonal neutral wind speed are thought to play the primary roles, the involvement of the meridional neutral wind speed in the formation of these irregularities is debatable. Using ground- and space-based measurements, the impact of the trans-equatorial wind's latitudinal gradient on the local post-sunset irregularities has not yet been studied. Furthermore, although the asymmetry of the equatorial ionization anomaly (EIA) is thought to be caused by the trans-meridional wind speed, which in turn in uences the occurrence of irregularities, the relationship between the global meridional wind speed and irregularity occurrence has not yet been studied using space and ground based observations. These problems are investigated using observations from space and the ground. F-region meridional neutral wind speeds from GOCE satellites and ground-based GNSS TEC have been used in the years 2012 and 2013. The rate of change of the TEC index (ROTI) is derived and employed as an indicator of post-sunset equatorial ionospheric irregularities. Using ground- and space-based data from three longitudinal sectors (Eastern Africa, Eastern South America, and Eastern Asia) the day-to-day variations of the local ionospheric irregularities due to the latitudinal gradient of the meridional wind speed are studied. In addition to the data from the ionospheric irregularity indicator, the variation in electron density from the Communication/Navigation Outage Forecasting System (CNOF/S) is also included. Correlational analysis is performed between the ROTI and the latitudinal gradient of the meridional neutral wind speed in each of the three longitudinal sectors. It is found that non-irregular ionospheric phenomena are observed when the gradient of the meridional neutral wind pro le with respect to geographic latitude is positive, whereas post-sunset ionospheric plasma irregularities are supported when the latitudinal gradient of the meridional wind is negative. In addition, a statistical analysis is conducted to examine viii the in uence of the global meridional neutral wind speed asymmetry on the occurrence of irregularities. To do this, the relationship between ionospheric irregularities and the meridional neutral wind speed di erence between the northern and southern positions of the EIA crests, which can lead to the asymmetry of the EIA and associated ionospheric conductivity, is investigated. The results show a strong relationship between ROTI values and the di erences in meridional neutral wind speeds at the EIA crests in the north and south. Moreover, we nd that the occurrence of post-sunset ionospheric irregularities is supported by lower wind speed di erence (less than 5 m/s) between the north and south EIA crests, but not by higher speed di erences (more than 5 m/s). The endings of this thesis study enrich our knowledge of the relationship between post-sunset equatorial ionospheric irregularities and meridional neutral wind speed.	en_US
dc.language.iso	en_US	en_US
dc.subject	Physics	en_US
dc.title	The Role of Meridional Neutral Winds On The Occurrence of Post-Sunset Equatorial Ionospheric Irregularities	en_US
dc.type	Thesis	en_US