Estimation of foF2 Using Global Model of Ionospheric Slab Thickness (GMIST) During January 15, 2022 Tonga Eruption

The performance of the global model of ionospheric slab thickness (GMIST) in terms of F2 layer critical frequency (foF2) estimation is evaluated during ionospheric disturbances caused by Hunga Tonga-Hunga Ha’apai (HTHH) eruption on January 15, 2022. Hourly values of foF2 estimation using GMIST with TEC input of global ionospheric map (GIM) are compared with foF2 observations from ionosonde stations. For this purpose, the correlation coefficient and deviation are calculated at different locations of ionosonde stations. The GMIST foF2 and ionosonde foF2 at the nearest HTHH have the largest at about 5MHz and the longest deviation during about 14 hours. The trend of the deviation decreases as the distance of ionosonde stations from HTHH increases. The trend indicates the effect of HTHH eruption on the ionosphere involves neutral wind that causes total electron content and foF2 are decrease in different levels. Meanwhile, the correlation coefficients between GMIST foF2 and ionosonde foF2 are not influenced by HTHH eruption. The results show that the HTHH eruption affects the GMIST foF2 performance, especially near the epicenter. Overall the daily mean absolute deviations vary from 0.3 MHz – 1.55 MHz. Hence the GMIST model is feasible to be used for HF communication prediction, especially during quiet ionospheric conditions, and necessary to be updated using real time ionosonde observation, especially after extreme vulcano eruption.