- 1Istituto Nazionale di Geofisica e Vulcanologia, Roma, Rome, Italy (alessio.pignalberi@ingv.it)
- 2The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
- 3Department of Navigation and Positioning, Finnish Geospatial Research Institute (FGI), Espoo 02150, Finland
- 4Department of Electrical Engineering, Computer Engineering and Informatics, Frederick University, Nicosia, Cyprus
- 5School of Engineering, University of Birmingham, Birmingham, UK
- 6Department of Earth and Environmental Sciences, Ludwig Maximilian University of Munich (LMU), Munich, Germany
- 7Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, France
NeQuick is a global empirical model describing the median climatological behavior of the electron density in the ionosphere–plasmasphere system. NeQuick allows a fast calculation of total electron content (TEC) values up to GNSS heights by numerical integration of the modeled electron density profile, making the model valuable for use in many geodetic and space weather applications. To ensure the highest reliability in TEC predictions, an accurate description of the topside ionosphere region and of the overlying plasmasphere is fundamental since they contain the largest fraction of TEC.
NeQuick describes the topside ionosphere and its plasmaspheric extension with a single semi-Epstein layer anchored to the F2-layer peak with a height-dependent effective scale height H, which is empirically formulated based on three topside parameters: H0, g, and r. H0 is the scale height value at the F2-layer peak; g represents the scale height vertical gradient near the F2-layer peak; while r is the parameter controlling the H behavior very distant from the F2-layer peak, namely, in the plasmasphere. While the H0 and g parameters can be reliably estimated based on COSMIC/FORMOSAT-3 (COSMIC-1) radio occultation (RO) profiles, the r parameter requires a different approach due to the limited altitudinal extension of COSMIC-1 RO profiles. To constrain the r parameter, we complemented COSMIC-1 RO profiles with TEC values from precise orbit determination (POD) antennas from the same satellites. POD TEC values are representative of the electron content of the upper part of the topside ionosphere (above the COSMIC-1 satellites) and of the plasmasphere.
The r parameter optimization is based on a twofold procedure. First, given a specific RO profile, H0, g, and r parameters are obtained from the topside section of the RO profile; thereafter, H0 and g are kept fixed while r, starting from the first-guess value obtained from the RO profile, is varied until it matches the topside TEC value obtained by adding the TEC measured by the POD antenna to the TEC of the RO topside section. In this way, the optimized r parameter improves the description of H in the plasmasphere and then the NeQuick modelling of the electron density in this region.
The proposed procedure has been applied to RO profiles and POD TEC values from the whole dataset of COSMIC-1 observations recorded between the years 2006 and 2020. Spatial and time variations of the optimized r values have been studied and compared with previous values obtained by only RO profiles. The reliability of the optimized r values has been tested by calculating H values in the plasmasphere through the NeQuick formulation and comparing them with the corresponding values obtained by Van Allen probes observations. These advancements are presented and discussed in view of the development and implementation of a revised NeQuick topside ionosphere model.
How to cite: Pignalberi, A., Nava, B., Prol, F., Haralambous, H., Themens, D., Smirnov, A., Pezzopane, M., and Coïsson, P.: Enhancing the NeQuick model performance in the topside ionosphere and plasmasphere through radio occultation and POD TEC observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9588, https://doi.org/10.5194/egusphere-egu25-9588, 2025.
