Modeling Center-of-Mass of the Ionosphere From the Slab-Thickness

The present study explores the center-of-mass (Hc) of the ionosphere as the effective ionospheric varying shell height (VSH). We presents global ionospheric maps GIM-Hc produced with IRI-Plas model by assimilating the instant GIM-TEC maps provided by JPL from 1994 to present which allows obtaining global maps of the F2 layer critical frequency, GIM-foF2 (or NmF2) and peak height, GIM-hmF2. Ratio TEC/NmF2 represents the slab-thickness model of the ionosphere, GIM-tau, fitted to foF2, hmF2 peak at each cell of a map. The slab-thickness tau is for the first time tied to hmF2 peak height with its components tau bot below hmF2 and topside tau top. Equations for evaluating Hc with IRI-Plas and NeQuick models are derived from Ne(h) profile complemented with the total electron content-height profile TEC(h) from the bottom boundary of the ionosphere (65-80 km over the Earth) to varying altitude h up to 20,200 km (GPS orbit). The position of Hc depends on the altitude range selected at the ionosphere and plasmasphere. We determine Hc from Ne(h) and TEC(h) profile within the borders of tau from the bottom side (hmF2 - tau bot) to topside (hmF2 + tau top). Regression linear model of Hc variation with hmF2 is derived which allows estimate of Hc from the F2 layer peak height hmF2. Statistical characteristics of GIM-Hc maps can serve for validation and updating the effective shell height with Hc parameter varying over the globe for improved vertical TEC evaluation from the slant TEC observations.