Adaptive modeling of equatorial ionization anomaly crest parameters by using multistation ionosonde data over the Indian region

The paper explores the new technique to study the temporal and spatial variation of equatorial ionization anomaly (EIA) by using the limited number of ground based observing stations. The technique involved the use of the Gaussian fitting over the latitudinal distribution of foF2. The multi-station F2-region critical frequency (foF2) data observed by ionosonde system during the 19^th (1954-1964) solar cycle is used for the present study. Results obtained by this analysis method suggest that the EIA crest exhibits the feature of latitudinal shifting and expansion in coverage area with increasing solar activity. The present results have been discussed in the light of relative contribution from transequatorial interhemispheric neutral wind and the strength of the equatorial fountain process. The study is further extended to derive the relationship between location and foF2 of the EIA crest by using the regression analysis which has been performed for the first time over the Indian sector. The results obtained by this analysis can be used to predict the latitudinal position and foF2 of the EIA crest for any given smoothed sunspot number. Results show that the predicted values by using this new approach is better as compared to the International Reference Ionosphere model-2001 predictions and hence the technique can be used for the adaptive modeling of EIA.