Validation of NeQuick 2 model over West African equatorial region using GNSS-derived Total Electron Content data

Abstract

The NeQuick 2 has been implemented as a climatological model with the goal to represent the typical median conditions of the ionosphere. Several investigations have been made to test its performances at global and regional scale. In order to provide a 3D specification of the electron density of the ionosphere at a given geographic location and time, specific data ingestion techniques, based on NeQuick 2 adaptation to Total Electron Content (TEC) data, have been introduced. In the present work, the performance of the NeQuick 2 model for climate prediction of TEC has been evaluated in the west African equatorial region. Several types of solar indexes such as the smoothed monthly mean sunspot number (R12), the daily solar radio flux at 10.7 cm wavelengths (F10.7) and the daily sunspot number (Rz) have been used as input parameters for the model. The monthly medians of the modeled vertical TEC (vTEC) have been compared to the corresponding monthly medians of the vTEC obtained from two Global Navigation Satellite System (GNSS) stations located in Côte d'Ivoire. Furthermore, to assess the “weather-like” capabilities of the model, a data ingestion technique has been implemented through the computation of an effective parameter Az at a single GNSS station in Côte d'Ivoire (Yamoussoukro). For geomagnetically disturbed and quiet days, this Az parameter has been used as input for NeQuick to estimate the vertical TEC values in another station (Abidjan) located at about 200 km from the previous one. Additional tests based on the evaluation of Az at the station of Cotonou in Benin allowed analysing the model capability of reconstructing TEC at different distances (up to 850 km from the reference station) according to the north-south and east-west directions of displacement. The statistical analysis has been based on relative frequencies distribution of the difference between reconstructed and the corresponding observed TEC.