Comparing IRI and a regional model with ionosonde measurements in Pakistan

Abstract We have used the technique of expansion in Empirical Orthogonal Functions (EOFs) to develop regional models of the critical frequencies of E and F 2 layers ( f o E,  f o F 2 ), peak height ( h m F 2 ), and semi-thickness of F 2 layer ( Y m F 2 ) over Pakistan. In the present study levels of solar activity specified by Smoothed Sunspot Number ( R ) from 10 to 200 are taken into account. The magnetic dip angle for the model ranges from 30° to 60°. We have compared the regional model and the International Reference Ionosphere (IRI) with measurements of three ionosondes in Pakistan. The model parameters f o E and f o F 2 are found overall comparable to the observed hourly median values during daytime at Karachi (geographic latitude = 24.95°N, longitude = 67.13°E, magnetic inclination = 37°), Multan (30.18°N, 71.48°E, 45°) and Islamabad (33.75°N, 73.13°E, 51.5°) during the years 1988, 1996 and 2000. For h m F 2 the computed values by regional and IRI model for the year 1995 are found close to each other. However, for Y m F 2 the results are better during daytime as compared to nighttime.