Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data

Fabricio S Prol,M Mainul Hoque

doi:10.3390/rs13081559

Abstract

A 3D-model approach has been developed to describe the electron density of the topside ionosphere and plasmasphere based on Global Navigation Satellite System (GNSS) measurements onboard low Earth orbit satellites. Electron density profiles derived from ionospheric Radio Occultation (RO) data are extrapolated to the upper ionosphere and plasmasphere based on a linear Vary-Chap function and Total Electron Content (TEC) measurements. A final update is then obtained by applying tomographic algorithms to the slant TEC measurements. Since the background specification is created with RO data, the proposed approach does not require using any external ionospheric/plasmaspheric model to adapt to the most recent data distributions. We assessed the model accuracy in 2013 and 2018 using independent TEC data, in situ electron density measurements, and ionosondes. A systematic better specification was obtained in comparison to NeQuick, with improvements around 15% in terms of electron density at 800 km, 26% at the top-most region (above 10,000 km) and 26% to 55% in terms of TEC, depending on the solar activity level. Our investigation shows that the developed model follows a known variation of electron density with respect to geographic/geomagnetic latitude, altitude, solar activity level, season, and local time, revealing the approach as a practical and useful tool for describing topside ionosphere and plasmasphere using satellite-based GNSS data.

Highlights

It is important to mention that slant TEC (STEC) measurements are obtained above the low Earth orbit (LEO) satellite
At the peak of the ionosphere, the proposed method based on Radio Occultation (RO) has provided a similar level of accuracy as NeQuick, revealing that Global Navigation Satellite System (GNSS)-based RO inversion can present the peak of the ionosphere with a similar level of accuracy as the method recommended by ITU
Significant improvements were obtained in comparison to NeQuick when validated against external vertical TEC (VTEC) data from METOP and Ne data from DMSP and Van Allen Probes

Summary

Introduction

The assimilation of Ne profiles and TEC values into a unique solution has continued to be a relevant challenge to any ionospheric/plasmaspheric system Empirical models such as NeQuick [1] and the International Reference Ionosphere extended to Plasmasphere (IRI-Plas) [2] are often used to describe the electron density profiles from 60 km up to the GNSS orbit altitude around 20,000 km. Gulyaeva [5], for instance, has upgraded the IRI-Plas model using ground-based TEC observations from Global Ionospheric Maps (GIMs), but this approach deals with the difficulties of separating the bottomside TEC contribution from the topside TEC This makes the use of satellite-based TEC to estimate electron.

Methods

Results

Conclusion