4:30 PM - 4:45 PM
[MTT37-10] Traveling Ionospheric Disturbances Following the 2024 Noto Peninsula Earthquake: Total Electron Content Observations by Ultra-Dense GNSS Receiver Networks
Keywords:GNSS, GPS, ionosphere, acoustic wave
Traveling Ionospheric Disturbances (TIDs), which are wavy structures of electron density perturbations in the ionosphere, have been observed following earthquakes and tsunamis. From Global Navigation Satellite System (GNSS) data, we can obtain Total Electron Content (TEC). The dense-GNSS receiver network is a power full tool to disclose horizontal two-dimensional structures of TIDs.
In this study, we applied a computerized ionospheric tomography (CIT) technique to TEC data collected from over 4,500 GNSS receivers operated in Japan by SoftBank Corp. and the Geospatial Information Authority of Japan. Our aim was to investigate the 3D structure of TIDs following the 2024 Noto Peninsula Earthquake, which occurred with a magnitude of 7.5 at 07:10 UT on January 1, 2024.
At 07:19 UT, an initial perturbation of TEC, possibly due to the earthquake, was observed. The time delay from the earthquake occurrence to the initial response in the ionosphere was 9 minutes, consistent with the idea that acoustic waves launched by the earthquake propagate upward at the speed of sound into the ionosphere. TEC perturbations propagated radially at a velocity of approximately 1000 m/s, corresponding to the sound velocity in the thermosphere.
The electron density perturbations reconstructed by the CIT technique revealed vertical structures possibly caused by acoustic waves. On a meridional and vertical cross-section of the electron density perturbations above the epicenter, an electron density enhancement with a phase front elongating from north-up to south-down was observed at 07:20 UT. This enhancement propagated southward, with the propagation velocity higher at higher altitudes than at lower altitudes, resulting in a change in the tilt angle of the phase-front of the electron density enhancement. Over time, the phase-front propagated southward and approached becoming vertical.
To understand this feature, we conducted model calculations of the ray paths of acoustic waves launched from the ground and propagating into the thermosphere/ionosphere. We found that the temporal variation of the phase-front of electron density perturbations can be interpreted in terms of the acoustic waves, whose velocity is higher at higher altitudes because the sound speed is proportional a square root of the ambient temperature.
The GNSS observation data from SoftBank used in this study were provided by SoftBank Corp. and ALES Corp. through the Consortium to utilize the SoftBank original reference sites for Earth and Space Science.
In this study, we applied a computerized ionospheric tomography (CIT) technique to TEC data collected from over 4,500 GNSS receivers operated in Japan by SoftBank Corp. and the Geospatial Information Authority of Japan. Our aim was to investigate the 3D structure of TIDs following the 2024 Noto Peninsula Earthquake, which occurred with a magnitude of 7.5 at 07:10 UT on January 1, 2024.
At 07:19 UT, an initial perturbation of TEC, possibly due to the earthquake, was observed. The time delay from the earthquake occurrence to the initial response in the ionosphere was 9 minutes, consistent with the idea that acoustic waves launched by the earthquake propagate upward at the speed of sound into the ionosphere. TEC perturbations propagated radially at a velocity of approximately 1000 m/s, corresponding to the sound velocity in the thermosphere.
The electron density perturbations reconstructed by the CIT technique revealed vertical structures possibly caused by acoustic waves. On a meridional and vertical cross-section of the electron density perturbations above the epicenter, an electron density enhancement with a phase front elongating from north-up to south-down was observed at 07:20 UT. This enhancement propagated southward, with the propagation velocity higher at higher altitudes than at lower altitudes, resulting in a change in the tilt angle of the phase-front of the electron density enhancement. Over time, the phase-front propagated southward and approached becoming vertical.
To understand this feature, we conducted model calculations of the ray paths of acoustic waves launched from the ground and propagating into the thermosphere/ionosphere. We found that the temporal variation of the phase-front of electron density perturbations can be interpreted in terms of the acoustic waves, whose velocity is higher at higher altitudes because the sound speed is proportional a square root of the ambient temperature.
The GNSS observation data from SoftBank used in this study were provided by SoftBank Corp. and ALES Corp. through the Consortium to utilize the SoftBank original reference sites for Earth and Space Science.