Assessment of improvement of the IRI model for foF2 variability over three latitudes in different hemispheres during low and high solar activities. (March 2021)

• Record Type: Journal Article
• Authors: Timoçin, Erdinç; Temuçin, Hüseyin; Inyurt, Samed; Shah, Munawar; Jamjareegulgarn, Punyawi
• Is Part Of: Acta astronautica. Volume 180(2021)
• Page Start: 305
• Page End: 316
• Publication Date: 2021-03
• Subjects: International reference ionosphere (IRI-2016) -- Ionosphere -- F2 layer critical frequency -- Solar activity; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2020.12.042
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: This paper discusses the diurnal and seasonal variations of the F2 layer critical frequency (foF2) and the improvement of performance of the IRI-2016 model in predicting foF2 over three latitudes in different hemispheres during low and high solar activities. We extracted the foF2 data from six ionosonde stations which are Manila (14.7 o N, 121.1 o E), Yamagawa (31.2 o N, 130.6 o E), Yakutsk (62.0 o N, 129.6 o E), Townsville (19.6 o S, 146.8 o E), Hobart (42.9 o S, 147.3 o E) and Terre Adelie (66.6 o S, 140.0 o E). The data of both low solar activity (LSA) period and high solar activity (HSA) periods were divided into three seasons as Northern Summer (May, June, July and August), Equinoxes (March, April, September and October) and Northern Winter (November, December, January and February). The present study showed that the IRI-2016 performance is strongly dependent on the solar activity, latitude, season, local time and hemisphere. For both hemispheres, the foF2 values at low latitude station are larger than those at middle latitude station, whereas the foF2 values at middle latitude station are larger than those at high latitude station. The agreement between IRI2016-modelled foF2 and foF2 measurements on all stations selected in the northern hemisphere is best for North Summer and worst for North Winter. For northern hemisphere, the values of relative deviations during both solar activities are largest in high latitudes and smallest in middle latitudes. As for southern hemisphere, the values of relative deviations during LSA are largest in middle latitudes and smallest in high latitudes, whereas the values of relative deviations during HSA are largest in low latitudes and smallest in high latitudes. It is thought that the relative deviations in the observed foF2 values are caused by solar activity that strongly alter chemical and electromagnetic processes in the ionosphere. These results are important for future improvements depending on solar activity and seasons in the IRI model for foF2 values over three latitudes in different hemispheres. Highlights: The IRI-2016 performance is strongly dependent on solar activity, latitude, season and local time. Relative deviations in the observed foF2 for Northern Summer and Northern Winter are asymmetry between northern and southern hemispheres. The IRI-2016 model needs to be improved for different solar activity. IRI-2016 performance is better during Northern Summer as compared to other seasons for both hemispheres.