The 3D EDD version of the TaD Model

The TSM-assisted Digisonde (TaD) Profiler (TaD model) is a topside profiler for the electron density profile based on empirical equations derived from topside sounding data of the Alouette/ISIS database and ingests the Digisonde observations at the height of the maximum electron density and the TEC parameters to adjust the profiler with the actual conditions of the ionosphere. The model has three components: (a) the Topside Sounders Model (TSM) subroutine (Kutiev and Marinov 2007; Kutiev et al. 2006) that provides the empirical functions for the O+/H+ transition height (hT), the topside electron density scale height (HT) and their ratio RT = HT/hT, derived solely from the Alouette/ISIS data; (b) the Topside Sounders Model Profiler (TSMP) subroutine (Kutiev et al. 2009a, 2009b) that offers analytical formulas for obtaining the shape of the vertical plasma distribution in the topside ionosphere and plasmasphere based on TSM parameters and on the F layer maximum density (NmF2), its height (hmF2) and its scale height (Hm) at its lower boundary, derived from Digisondes. This profiler models separately the O+ and H+ density distributions in transition region between the topside F region and plasmasphere, extracted from the analysis of the electron density profiles from ISIS-1; (c) the final TaD subroutine that performs the necessary transformations to the Digisonde autoscaled scale height so that the integrated TSMP electron density from the F layer peak to GNSS orbits can be finally adjusted to the measured GNSS TEC at the Digisonde location (Belehaki et al. 2012; Kutiev et al. 2012). The 1-dimensional (1D) Electron Density Distribution (EDD) version of the TaD Model takes as input (a) the ionospheric characteristics at the hmF2 altitude, from a Digisonde sounder that can be retrieved from the SAO file and (b) the TEC parameter, which is the vertical electron content at the station location (i.e., the height integral of the electron density from 90 to 22000 km); the vertical TEC can be extracted from a TEC map such as the maps released by DLR or CODE, but it can also be calculated based on a single station solution code, with RINEX data received by a GNSS receiver co-located with the Digisonde. The topside profile is extrapolated with the TaD model as described above. This version does not provide the electron density profile (Ne) below hmF2 but calculates the bottomside TEC (bTEC) by approximating Ne distribution by the a-Chapman formula. The output of the code is the electron density profile over the ionosonde station. The 3-dimensional (3D) Electron Density Distribution (EDD) version of the TaD Model takes as input bottomside electron density grids up to the heights of the maximum density using fitting technique (Stanislawska et al. 2003) and the NeQuick 2 (Nava et al., 2008) as background model. The 1D version of the EDD of the TaD model is applied at each grid point for the topside extrapolation.