Global median model of the F2-layer peak height based on ionospheric radio-occultation and ground-based Digisonde observations

Abstract

In this article, we present a global median model of the ionospheric F2-layer peak height (h m F2), which we named Satellite and Digisonde Model of the F2 layer (SDMF2). This model is based on the radio-occultation data of the satellite missions CHAMP (2001-2008), GRACE (2007-2011), COSMIC (2006-2012) as well as the ionospheric sounding data from the 62 Earth-based Digisonde sounders (1987-2012). As the input parameters, the model uses the year, month and time UT as well as the geographic coordinates and F 10.7 index averaged over the 3 Sun rotations (F 10.7A ). The SDMF2 model is based on the spherical functions decomposition with the 12 harmonics for the longitude and the 8 ones for the modified dip latitude (MODIP). For the diurnal variations, we used the 3 Fourier harmonics. We assumed that the dependency of h m F2 on F 10.7A index is logarithmic. The model accurately reproduces both the spatial and temporal behavior of the monthly h m F2 median. The root-mean-square (RMS) and the mean relative deviations (MRD) from the original data are MRD ∼ 3.7%, RMS ∼ 14.3 km and MRD ∼ 5.4%, RMS ∼ 23.4 km for the periods of low and high solar activity, respectively. The large initial dataset allows achieving the higher accuracy than International Reference Ionosphere model (IRI), and this is confirmed by comparing the SDMF2 model with independent data.