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Two-mode long-distance propagation of coseismic ionosphere disturbances

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Title: Two-mode long-distance propagation of coseismic ionosphere disturbances
Authors: Astafyeva, Elvira Browse this author
Heki, Kosuke Browse this author →KAKEN DB
Kiryushkin, Vladislav Browse this author
Afraimovich, Edward Browse this author
Shalimov, Sergey Browse this author
Issue Date: 15-Oct-2009
Publisher: American Geophysical Union
Journal Title: Journal of Geophysical Research. Space physics
Volume: 114
Issue: A10
Start Page: A10307
Publisher DOI: 10.1029/2008JA013853
Abstract: Using GPS total electron content (TEC) measurements, we analyzed ionosphere response to the great Kurile earthquake of 4 October 1994. High spatial resolution of the Japanese dense array of GPS receivers (GEONET) provided us the unique opportunity to observe the evolution of coseismic ionospheric disturbances (CID) which propagated for more than 1800 km away from the epicenter. Plotting a travel-time diagram for the CID and using an "array processing" technique within the approximation of a spherical CID wave front, we observed a phenomenon of CID separation into two modes and we found that characteristics of the CID depend on the distance from the epicenter. The maximum of the CID amplitude was observed at ~500 km from the epicenter. Within the first 600-700 km, the CID propagation velocity was about 1 km/s that is equal to the sound speed at the height of the ionospheric F-layer. Starting from ~600-700 km out from the epicenter, the disturbance seems to divide into two separate perturbations, with each propagating at a different velocity, about 3 km/s for the one and about 600 m/s for the other. Apparently, the TEC response in the far field of the CID source is a mixture of signals that further "splits" into two modes because of the difference in their velocities. Our observations are in good agreement with the results of space-time data processing in the approximation of a spherical wave front of CID propagation.
Rights: An edited version of this paper was published by AGU. Copyright 2009 American Geophysical Union.
Type: article (author version)
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 日置 幸介

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