Traveling Ionospheric Disturbances Observed Over South America After Lithospheric Events: 2010–2020

摘要

Here, the ionospheric response to earthquakes, earthquakes inducing tsunamis, and volcanic eruptions are presented as a contribution to the so-called ionospheric seismology with the eventual development of real-time warning systems in mind. A thorough analysis of Traveling Ionospheric Disturbances (TIDs) observed after these lithospheric events in South America is presented. It is based on a decade of total electron content (TEC) anomaly maps constructed explicitly for this purpose, likely the most extensive survey ever for South America. Three disturbance types are identified: TIDs generated by shock-acoustic waves, by gravity waves, possibly induced by tsunami waves, and by Rayleigh surface waves. TIDs are observed after earthquakes with epicenters on the Pacific Ocean east coast, except one in the middle of the ocean. TIDsgenerating earthquake thresholds are found to be Mw ≥ 7.0 and depth ≤40, and TID amplitudes and ranges are proportional to earthquake magnitude. Fault mechanism and satellite-receiver pair geometry are also considered. TIDs after volcanic eruptions confirm that atmospheric resonances are already reported. TIDs propagation direction depends strongly on the geomagnetic field direction, propagation toward the geomagnetic equator being more efficient. It was only possible to add some kind of vertical disturbance-propagation evidence to TEC TIDs identification in some cases using ionograms from nearby ionosondes. A denser ionosonde network with greater sounding frequency would be necessary for further study.