foF2 variability at the southern low latitude station and the performance of IRI-2016 model during ascending phase of solar cycle-24

Abstract In this research work, we have analyzed the data of critical frequency of the F2 region ionosphere over southern low latitude station COCO (Keeling) Island (Geog. Lat. 12.20⁰S; Geomag. Lat. 22.83⁰S; Geog. Long. 96.80⁰E) for the period 2009-2013 and result thereof have compared with the IRI-2016 model. Our analysis shows a good correlation between variations in foF2 and solar flux at F10.7 cm wavelength. With concern to geomagnetic activity during the period 2009-2013, it has found that the variability in the monthly mean Ap index remained below 20 nT throughout the period 2009-2013. Concerning quiet time F2 region variability, our results explicated the solar cycle, semiannual, and seasonal/annual variation in foF2. Similar oscillations in foF2 have been explored using the Lomb-Scargle Periodogram technique. We have also observed the fundamental mode (27 days) and its overtones (9 and 13-day) in the geomagnetic activity parameter (Ap). Analysis of foF2 showed the consistent presence of the semiannual anomaly and absence of the winter anomaly during the ascending phase of solar cycle-24. A presence of an annual component in normalized foF2 has been examined using regression analysis. A comparative study of ionosonde observed foF2 with IRI-2016 modeled foF2 showed that the general ionospheric trends in IRI predictions are consonant with the observations for the diurnal, seasonal, and solar cycle variation. However, a deviation in the amplitude of foF2 up to the order of 5 MHz depending upon local time, seasons, and phases of the solar cycle has observed.