Ionospheric perturbation indices based on the low- and high-orbiting satellite radio tomography data

Methods are suggested for constructing ionospheric perturbation indices (IPIs) based on empirical radio tomographic (RT) electron density distributions taking into account spatiotemporal resolution, and coverage of low- and high-orbiting (LO and HO) RT data. The LORT-based IPIs are calculated as spatial root mean square values of electron density derivatives indicating the presence of local ionospheric structures on a spatial scale of dozens of kilometers. The HORT-based IPIs are based on the statistical characteristics, i.e., means and deviations from the means, of electron density or vertical TEC distributions with different normalizations and subsequent spatial averaging, which take into account the geomagnetic activity and seasonal behavior of ionospheric plasma. Various schemes of IPIs construction are considered, correlations between IPIs and geomagnetic Kp index are analyzed, the indices most sensitive to geomagnetic activity are identified, and additional modifications of computational algorithms enhancing this sensitivity are suggested.