The geoeffectiveness of TIE-GCM simulations of ionospheric critical frequency foF2 at the equatorial station of Thiruvananthapuram in the Indian sector

Abstract

An extensive intercomparison of ionospheric foF2 observations and NCAR Thermosphere-Ionosphere ElectrodynamicsGeneral Circulation Model(TIE-GCM)simulations has been carried out for the dip equatorial location of Thiruvananthapuram. Ionosonde measurements for geomagnetically quiet days of 2002, 2006 and 2008, representing solar maximum, solar minimum and deep solar minimum conditions have been used for the analysis.In general TIE-GCM simulations reproduced the temporal and seasonal characteristics of foF2 over Thiruvananthapuram reasonably well for all the three solar activity conditions. Seasonally the difference between the measured and the simulated foF2 tended to be higher during winter (maximum of 25%). Additionally, it is found that TIE-GCM is not reproducing the reduction in the foF2 values in the noon hours i.e. the bite out, which is very prominent in the foF2 observations predominantly during 2002. A detailed analysis revealed that, there is good agreement between the modeled and measured values for the whole observation period, with an R value of 0.81. From the comparison it is clear that the model underestimates the observations in general but for the periods when bite out is prominent, the model gives an over estimation.The comprehensive comparisons during different solar activity conditions have shown that the difference between modeled and measured ionospheric peak densities lies in the range of.10 to −25%. This study brings out the efficacy of the model in simulating the temporal seasonal and solar cycle variability of ionospheric foF2 over the equatorial Indian region.