Simulated GNSS Observation of Traveling Ionospheric Disturbance from Ground Receivers

摘要

Traveling Ionospheric Disturbances (TID) can be induced by acoustic waves in the neutral atmosphere, allowing such process to be observed as changes in the trans-ionospheric GNSS signal. Coherence between measurements from different stations within a large, dense GNSS network has been used to identify and characterize various TIDs. In order to evaluate the sensitivity, accuracy and possible biases of this technique, a simulator has been developed. The magneto-hydrodynamic (MHD) equations were simplified through assumptions about the time scales of various processes, and the interactions between ions and electrons in the ionosphere. A raytrace method was used propagate the acoustic wave from the surface and the problem was approximated as axially symmetric about the point source location, allowing a two-dimensional cylindrical coordinate system to be used. These model simplifications were necessary to produce a numerically efficient algorithm capable of simulating hundreds of GNSS ray paths, in order to represent the response over a large network. Ground motion observed during the 2011 Tohoku earthquake and tsunami was used to define the input signal. Synthetic waveforms produced from the model were found to agree well with the GNSS observations made in Japan during that event. Arrival time errors showed geographical correlation with the distance form the epicenter, indicating the limitations of the pointsource approxiamation.