Estimation of $hmF2$ and $foF2$ Communication Parameters of Ionosphere $F2$-Layer Using GPS Data and IRI-Plas Model

F2-layer is the most important and characteristic layer of the ionosphere in the propagation of high frequency (HF) waves due to the highest level of conductivity in the propagation path. In this study, the relation of Total Electron Content (TEC) with the maximum ionization height (hmF2) and the critical frequency (foF2) of F2-layer are investigated within their defined parametric range using the IRI model extended towards the plasmasphere (IRI-Plas). These two parameters are optimized using daily observed GPS-TEC (IONOLAB-TEC) in an iterational loop through Non-Linear Least Squares (NLSQ) optimization while keeping the physical correlation between hmF2 and foF2 parameters. Optimization performance is examined for daily (24-hour) and hourly TEC optimizations separately. It is observed that hourly TEC optimization produces results with much smaller estimation errors. As a result of the hourly optimization, we obtain the hourly hmF2 and foF2 estimates as they are the optimization parameters. Obtained hmF2 and foF2 estimates are compared with the ionosonde estimates for various low, middle and high latitude locations for both quite and disturbed days of ionosphere. The results show that hmF2 and foF2 estimates obtained from IRI-Plas optimization (IRI-Plas-Opt) and ionosonde are very much in agreement with each other. These results also signify that IRI-Plas provides a reliable background model for ionosphere. With the proposed method, it is possible to build a virtual ionosonde via optimization of IRI-Plas model using the observed TEC values.