Research Article

New formulation for the topside ionosphere and plasmasphere based on NeQuick

¹ Department of Navigation and Positioning, Finnish Geospatial Research Institute (FGI), Espoo 02150, Finland
² School of Technology and Innovations, University of Vaasa, Wolffintie 32, 65200 Vaasa, Finland
³ Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via di Vigna Murata 605, 00143 Rome, Italy
⁴ Department of Earth and Environmental Sciences, Ludwig Maximilian University of Munich (LMU), Theresienstraße 41, 80333 Munich, Germany
⁵ GFZ Helmholtz Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany

^* Corresponding author: fabricio.dossantosprol@nls.fi

Received: 8 April 2025
Accepted: 27 September 2025

Abstract

The total electron content (TEC) affecting signal propagation of Global Navigation Satellite Systems (GNSS) is strongly influenced by the topside ionosphere and plasmasphere. This study introduces a new approach to representing the two regions. The developed topside ionosphere and plasmasphere model has been evaluated using TEC data from the COSMIC/FORMOSAT-3 mission, the Swarm-A satellite, and Global Ionospheric Maps (GIMs), covering the period from 2008 to 2024. Van Allen Probes data have also been used as a benchmark for the plasmasphere. All results have been obtained on the basis of a modified version of the NeQuick 2 model, named IonoMAP (Ionospheric Mapping). Although the new formulation for the topside ionosphere and plasmasphere still slightly underestimates TEC, it reduces biases to approximately 1–3 TECU and improves accuracy by 28–40% compared to the NeQuick 2 model formulation. These results suggest that the proposed model is a viable solution to improve current modeling of the topside ionosphere and plasmasphere.