Multi‐TID detection and characterization in a dense Global Navigation Satellite System receiver network

Abstract

The medium‐scale traveling ionospheric disturbances (MSTIDs) constitute the most frequent ionospheric wave signatures. We propose a method for detecting the number of simultaneous MSTIDs from a time series of high‐pass‐filtered Vertical Total Electron Content (VTEC) maps and their parameters. The method is tested on the VTEC map corresponding to a simulated realistic scenario and on actual data from dual‐frequency Global Positioning System (GPS) measurements gathered by +1200 GPS receivers of the GPS Earth Observation Network (GEONET) in Japan. The contribution consists of the detection of the number of independent MSTIDs from a nonuniform sampling of the ionospheric pierce points. The problem is set as a sparse decomposition on elements of a dictionary of atoms that span a linear space of possible MSTIDs. These atoms consist of plane waves characterized by a wavelength, direction, and phase on a surface defined, the part of the ionosphere sounded by the GEONET (i.e., 25°N to 50°N of latitude and 125°E to 155°E of longitude). The technique is related to the atomic decomposition and least absolute shrinkage and selection operator. The geophysical contribution of this paper is showing (a) the detection of several simultaneous MSTIDs of different characteristics, with a continuous change in the velocity; (b) detection of circular MSTID waves compatible by time and center with a specific earthquake; (c) simultaneous superposition of two distinct MSTIDs, with almost the same azimuth; and (d) the presence at nighttime of MSTIDs with velocities in the range 400–600 m/s.

ADDTID: An Alternative Tool for Studying Earthquake/Tsunami Signatures in the Ionosphere. Case of the 2011 Tohoku Earthquake

“…A further contribution of this work is that the ADDTID algorithm can estimate parameters of simultaneous perturbations in a given region, as was shown in Yang et al [1] and Yang et al [2]. This allows a clearer distinguishing of the properties of the overlapping gravity and acoustic waves.…”

“…Also, we provide diverse space weather indicators such as the geomagnetic and solar activities. These statistical results show that the these TIDs with very low intensity might not be related to the earthquake but the seasonal or diurnal characteristics, for instance the TIDs induced by the solar terminator during the spring equinox, see Yang et al [1], Kotake et al [37], Otsuka et al [38]. The low intensities of TIDs compared to the equatorward ones might show the weak effects of the solar terminator.…”

“…The ADDTID algorithm was designed to detect harmonic shapes (i.e., flat sine waves). Because perturbations appear suddenly (i.e., correspond to a transient), the current implementation detects correctly the direction, wavelength and intensity of propagation correctly, but the variability in the estimation of speed increases when the amplitude decreases, which is the case at hand, because of their low intensity of the initial high-speed TIDs, see Yang et al [1]. For clarity reasons, in the histograms the upper velocity was limited at 2400 m/s, while in the polar plots, the detected disturbances of higher speed, were represented at the border of the plot.…”

“…In this article, we will analyze the relationship between earthquake/tsunami signatures in the ionosphere, in the form of Traveling Ionospheric Disturbances (TIDs). We will do this using as a tool the Atomic Decomposition Detector of Traveling Ionospheric Disturbances (ADDTID) algorithm developed in Yang et al [1]. The article contribution is the use of a method for automatically characterizing the earthquake/tsunami interaction with the ionosphere from the GNSS signals.…”

“…Finally, with the ADDTID algorithm, the authors were able to determine tsunami-driven TIDs, see Yang et al [1]. The multi-TID characterization tool in contrast with other methods that require visual inspection, was able to automatically detect the partial circular fronts of TIDs whose center matched the epicenter of a small-scale earthquake/tsunami in Japan in 2011.…”