Ionosphere and Upper Atmosphere
Two-mode long-distance propagation of coseismic ionosphere disturbances
Article first published online: 15 OCT 2009
Copyright 2009 by the American Geophysical Union.
Journal of Geophysical Research: Space Physics (1978–2012)
Volume 114, Issue A10, October 2009
How to Cite
2009), Two-mode long-distance propagation of coseismic ionosphere disturbances, J. Geophys. Res., 114, A10307, doi:10.1029/2008JA013853., , , , and (
- Issue published online: 15 OCT 2009
- Article first published online: 15 OCT 2009
- Manuscript Accepted: 10 JUL 2009
- Manuscript Revised: 24 MAY 2009
- Manuscript Received: 27 OCT 2008
- ionosphere TEC;
 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 traveltime diagram for the CID and using an “array processing” technique within the approximation of a spherical CID wavefront, 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, which is equal to the sound speed at the height of the ionospheric F-layer. Starting from ∼600 to 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 wavefront of CID propagation.