Comparison between foF2 observations and IRI-2001 model predictions at Thailand equatorial latitude station

In this paper, the comparison between the F2-layer critical frequency (foF2) observations and International Reference Ionospheric (IRI) model predictions is presented. The data used for this study are obtained from bottomside ionogram recorded by the FM/CW ionosonde at Chumphon campus of King Mongkutpsilas Institute of Technology Ladkrabang (latitude 10.72degN and longitude 99.37degE), Thailand, located near the magnetic equator. The measurement data coverage from January to December of a low solar activity year (2006) is analyzed based on the diurnal, seasonal variation and then compared with IRI-2001 model predictions. Generally, the foF2 obtained from the IRI (URSI and CCIR) model closely follows observed foF2 values. Comparing the results of URSI and CCIR options for foF2, we find that for low solar activity, both the URSI and CCIR options of the IRI model give foF2 values close to the ones measured at Chumphon, but the CCIR results produce smaller range of deviation than the URSI results. All comparative studies give feedback for new improvements of CCIR and URSI IRI models.