Fluctuations on vertical profiles of the ionospheric electron density perturbed by the March 11, 2011 M9.0 Tohoku earthquake and tsunami
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The GPS radio occultation (RO) of FORMOSAT-3/COSMIC (F3/C) with 1–2.5-km-altitude resolution is used to scan fluctuations on vertical profiles of the ionospheric electron density induced by seismic and tsunami waves of the March 11, 2011 M9.0 Tohoku earthquake. The Hilbert–Huang transform is applied to derive the instantaneous wave number and amplitude of the fluctuations in 22 (7 before and 15 after) F3/C profiles within 3000 km in radius from the epicenter during the earthquake. Fluctuations of the vertical electron density profile induced by underneath Rayleigh and tsunami waves and their post-waves are examined. It is found that the right underneath Rayleigh wave can induce significant long-wavelength fluctuations of 50–105 km on the vertical profile of the electron density, while tsunami and their post-waves activate the prominent short-wavelength fluctuations less than 16 km on those profiles in the poleward side of the epicenter. Results show that RO is a powerful tool which is suitable to probe vertical fluctuations in the ionospheric electron density.
KeywordsGPS radio occultation Total electron content FORMOSAT-3/COSMIC Tsunami Rayleigh wave Tohoku earthquake Hilbert–Huang transform (HHT)
This work was finically supported by the Center for Astronautical Physics and Engineering (CAPE) from the Featured Area Research Center Program within the frame work of Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan. This study is supported by the grant of Ministry of Science and Technology to National Central University MOST 107-2119-M-008-018 and the ISSI-Bern International Team of Understanding Solid Earth/Ocean-Ionosphere Coupling (the team leader Makela J. (US) & Rolland L. (FR)). The support under the Grant 18-01969S by the Czech Science Foundation is also acknowledged. The authors acknowledge COSMIC Data Analysis and Archival Center (CDAAC, http://cosmic-io.cosmic.ucar.edu/cdaac/index.html) and Taiwan Analysis Center for COSMIC (TACC, http://tacc.cwb.gov.tw) for providing FORMOSAT-3/COSMIC radio occultation data. The authors wish to thank Ms. P. H. Lin for cartoon graphing, as well as reviewers’ useful comments and suggestions which significantly improve the presentation.
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