Improvement of Global Ionospheric TEC Derivation with Multi-Source Data in Modip Latitude

Abstract

Global ionospheric total electron content (TEC) is generally derived with ground-based Global Navigation Satellite System (GNSS) observations based on mathematical models in a solar-geomagnetic reference frame. However, ground-based observations are not well-distributed. There is a lack of observations over sparsely populated areas and vast oceans, where the accuracy of TEC derivation is reduced. Additionally, the modified dip (modip) latitude is more suitable than geomagnetic latitude for the ionosphere. This paper investigates the improvement of global TEC with multi-source data and modip latitude, and a simulation with International Reference Ionosphere (IRI) model is developed. Compared with using ground-based observations in geomagnetic latitude, the mean improvement was about 10.88% after the addition of space-based observations and the adoption of modip latitude. Nevertheless, the data from JASON-2 satellite altimetry and COSMIC occultation are sparsely-sampled, which makes the IRI TEC a reasonable estimation for the areas without observation. By using multi-source data from ground-based, satellite-based and IRI-produced observations, global TEC was derived in both geomagnetic and modip latitudes for 12 days of four seasons in 2014 under geomagnetic quiet conditions. The average root-mean-square error (RMSE) of the fitting was reduced by 7.02% in modip latitude. The improvement was largest in March and smallest in June.

Nighttime Midlatitude E‐F Coupling in Geomagnetic Conjugate Ionospheres: A Double Thin Shell Model and a Multi‐Source Data Investigation

“…Spaceborne GNSS radio occultation of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) have advantages of high accuracy and vertical resolution, which can complement the ground‐based GNSS observations with its global coverage (Fu, Ma, et al., 2021). Six satellites in COSMIC‐2 mission were operational after 25 June 2019, providing uniform global data coverage with several thousand electron density profiles daily, especially near the equatorial region (Cherniak et al., 2021).…”

Seasonal Features of the Ionospheric Total Electron Content Response at Low Latitudes during Three Selected Geomagnetic Storms

“…With the modified dip coordinate, the errors increase from midlatitude toward the auroral zone [22]. The use of the methodology is also included in the research and modeling of the global distribution of TEC from GPS observations using modip latitude [23][24][25].…”