Abstract
AbstractThe correct representation of global‐scale electron density is crucial for monitoring and exploring the space weather. This study investigates whether the ground‐based Global Navigation Satellite System (GNSS) tomography can be used to reflect the global spatial and temporal responses of the ionosphere under storm conditions. A global tomography of the ionosphere electron density is constructed based on data from over 2,700 GNSS stations. In comparison to previous techniques, advances are made in spatial and temporal resolution, and in the assessment of results. To demonstrate the capabilities of the approach, the developed method is applied to the March 17, 2015 geomagnetic storm. The tomographic reconstructions show good agreement with electron density observations from worldwide ionosondes, Millstone Hill incoherent scatter radar and in‐situ measurements from satellite missions. Also, the results show that the tomographic technique is capable of reproducing plasma variabilities during geomagnetically disturbed periods including features such as equatorial ionization anomaly enhancements and depletion. Validation results of this brief study period show that the accuracy of our tomography is better than the Neustrelitz Electron Density Model, which is the model used as background, and physics‐based thermosphere‐ionosphere‐electrodynamics general circulation model. The results show that our tomography approach allows us to specify the global electron density from ground to ∼900 km accurately. Given the demonstrated quality, this global electron density reconstruction has potential for improving applications such as assessment of the effects of the electron density on radio signals, GNSS positioning, computation of ray tracing for radio‐signal transmission, and space weather monitoring.
Highlights
Measuring the electron density in the ionosphere is an important step to improve our understanding of the solar-terrestrial environment impact on communication, surveillance, and navigation systems
In comparison to the background model Neustrelitz Electron Density Model (NEDM), it is clear that significant updates were performed by tomography, such as a more evident equatorial ionization anomaly (EIA) representation, as well as higher Vertical TEC (VTEC) values in the low-latitudes and lower VTEC values during the nighttime and at the high-latitudes
Maximum VTEC values during the quiet period are observed around 70 TECU (TEC Units), being 1 TECU = 1016 el/m2, and maximum VTEC values during the disturbed period are observed around 90–100 TECU at 18 UT
Summary
Measuring the electron density in the ionosphere is an important step to improve our understanding of the solar-terrestrial environment impact on communication, surveillance, and navigation systems. Several methods can be applied to estimate the three-dimensional (3D) electron density in the ionosphere (Bust & Mitchell, 2008). In this context, the computerized ionospheric tomography (CIT) gained attention in the last three decades since it provides accurate observations of the ionospheric electron density over large areas (Austen et al, 1988; Norberg et al, 2018). It has been demonstrated that these images can be used to describe the overall ionospheric plasma structure and its temporal evolution in the atmosphere They have been successfully used to represent important ionospheric dynamics, such as traveling ionospheric disturbances (Bolmgren et al, 2020; Chen et al, 2016), geomagnetic storm signatures
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