The Influence of Solar X-ray Flares on SAR Meteorology: The Determination of the Wet Component of the Tropospheric Phase Delay and Precipitable Water Vapor

Abstract

In this work, we study the impact of high-energy radiation induced by solar X-ray flares on the determination of the temporal change in precipitable water vapor (ΔPWV) as estimated using the synthetic aperture radar (SAR) meteorology technique. As recent research shows, this radiation can significantly affect the ionospheric D-region and induces errors in the estimation of the total electron content (TEC) by the applied models. Consequently, these errors are reflected in the determination of the phase delay and in many different types of measurements and models, including calculations of meteorological parameters based on SAR observations. The goal of this study is to quantify the impact of solar X-ray flares on the estimation of ΔPWV and provide an estimate of errors induced if the vertical total electron content (VTEC) is obtained by single layer models (SLM) or multiple layer models (MLM) (these models do not include ionosphere properties below the altitude of 90 km as input parameters and cannot provide information about local disturbances in the D-region). The performed analysis is based on a known procedure for the determination of the D-region electron density (and, consequently, the vertical total electron content in the D-region (VTECD)) using ionospheric observations of very low frequency (VLF) radio waves. The main result indicates that if the D-region, perturbed by medium-sized and intense X-ray flares, is not modeled, errors occur in the determination of ΔPWV. This study emphasizes the need for improved MLMs for the estimation of the TEC, including observational data at D-region altitudes during medium-sized and intense X-ray flare events.

Modelling of the Electron Density and Total Electron Content in the Quiet and Solar X-ray Flare Perturbed Ionospheric D-Region Based on Remote Sensing by VLF/LF Signals

“…This receiver was a part of the Stanford/AWESOME Collaboration for Global VLF Research (http://waldo.world/narrowband-data/, accessed on 5 November 2021). As in many previous studies (see, for example, [7,8,17]), we analyse the DHO signal because of the best quality of the recorded data. Consequently, the analytical expressions obtained in this study refer to the D-region over the part of Europe included within the transmitter (Rhauderfehn, Lower Saxony, Germany) and receiver (Belgrade, Serbia) locations.…”

“…Knowledge of Wait's parameters allows us to calculate the D-region electron density at the times t Φ max and t TEC Dmax using Equation (8). The corresponding values at 65 km, 75 km, and 85 km are shown in Figure 10, where the left and right panels refer to the times t Φ max and t TEC Dmax , respectively.…”

“…Consequently, this modelling can have practical application in technologies based on the propagation of satellite and groundbased signals, such as space geodesy and telecommunications. Namely, during intense perturbations of the D-region, its influence on the satellite signal delay is not negligible [7], which is consequently reflected in the determination of the ionospheric influence in many measurements (see, for example, [8]). Due to lower frequencies of ground based signals, the importance of D-region modelling is more pronounced in the determination of the characteristics of their propagation, which is significant in, for example, telecommunications.…”

“…Knowledge of the time evolutions β(t) and H (t) allows us to calculate the D-region electron density time-altitude distribution using Equation (8). In some analyses, the electron density time evolution needs to be fitted.…”

An Optimized Framework for Precipitable Water Vapor Mapping Using TS-InSAR and GNSS

“…It can be generated by the condensation of water vapor per unit area of the atmospheric column from the ground to the top of the atmosphere. It has a great significance in monitoring and predicting weather and studying global climate change [1][2][3]. Interferometric Synthetic Aperture Radar (InSAR), as a rapidly developing geodetic technology, has the characteristics of all weather, large scale, and high resolution [4][5][6][7].…”