Abstract
<p class="p0">This study aims to evaluate the performance of the global model of ionospheric slab thickness (GMIST) in terms of F2 layer critical frequency (foF2) estimation during geomagnetic disturbed conditions. Hourly values of foF2 as obtained from ionosonde stations located at equatorial, low- and mid-latitude regions are compared with the corresponding GMIST and IRI-STORM modeled values. For this purpose, the correlation coefficient, daily mean, root mean square error and improvement percentage are calculated at different regions and geomagnetic disturbance levels. The results show that GMIST is more accurate than IRI-STORM model in terms of foF2 estimation at low- and mid-latitude regions, while at equatorial areas GMIST is less accurate during geomagnetically disturbed and quiet conditions.</p>
Highlights
The total electron content (TEC), measured by means of navigation satellite systems such as GPS, GLONASS, GALILEO, has turned into a key parameter in the characterization and monitoring of ionosphere on a global scale
The global model of ionospheric slab thickness (GMIST) model underestimates the frequency of the F2 layer (foF2) observations and the IRI foF2 modeled values especially the foF2 minimum occurring before sunrise at the lowlatitude ionosphere (Figure 3b, right-lower panel) and mid-latitude Southern Hemisphere (Figure 3b, left-lower panel)
GMIST modeled foF2 values shows a good agreement with observational foF2 values during quiet and geomagnetic storm in the Northern Hemisphere mid-latitude region (Figure 3b, upper panel)
Summary
The total electron content (TEC), measured by means of navigation satellite systems such as GPS, GLONASS, GALILEO, has turned into a key parameter in the characterization and monitoring of ionosphere on a global scale. The spatial coverage of foF2 ionosonde observations is not globally uniform due to the high cost of acquiring and maintaining ionosondes. This limitation can be surpassed considering the abundance of GPS receiver networks that provide TEC observations which can be used jointly with ionospheric slab thickness models to improve the foF2 predictability and to provide support for various HF communication systems, radio amateurs and broadcaster operators. Houminer [1997] has reviewed the use of GPS data in relation to short-term foF2 prediction enhancement using one ionosonde station located in Cyprus and concluded that the high correlation between TEC GPS with foF2 (varying from 0.53 to 0.78) allows the use of GPS data for near real time foF2 map updating, both in temporal (short-term, medium and long-term) and in spatial (local, regional and global) terms. Houminer [1997] has reviewed the use of GPS data in relation to short-term foF2 prediction enhancement using one ionosonde station located in Cyprus and concluded that the high correlation between TEC GPS with foF2 (varying from 0.53 to 0.78) allows the use of GPS data for near real time foF2 map updating, both in temporal (short-term, medium and long-term) and in spatial (local, regional and global) terms. Kouris [2004] concluded that there is a high correlation between the TEC and the square of foF2 (around 0.8), ionospheric hysteresis is detected before and after noon time
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