Acoustic resonance and plasma depletion detected by GPS total electron content observation after the 2011 off the Pacific coast of Tohoku Earthquake

Abstract

Two-dimensional structures of the ionospheric variations generated by the acoustic resonance between the ground surface and the lower thermosphere was observed for the first time near the epicenter after the M 9.0 Tohoku earthquake on March 11, 2011. A short-period oscillation of total electron content was observed by a GPS receiver array after the earthquake for four hours in the vicinity of the epicenter. It was centered in the east of the epicenter where the tsunami was estimated to commence. The frequency of the dominant mode of the oscillation was 4.5 mHz, 222 seconds of period, while there were minor oscillations whose frequency were 3.7 mHz and 5.3 mHz. These periods are consistent with the periods of the acoustic resonance between the ground surface and the lower thermosphere, predicted by a numerical model. The amplitude of the TEC oscillation showed a gradual change of the amplitude. The two-dimensional distributions of TEC variations generated by this resonance had wave frontal structures that extended from northwest to southeast. The resonant oscillation of the TEC was accompanied by a depletion of TEC whose duration was about 60 minutes. The area of this depletion also centered on the epicenter.

Ionospheric disturbances detected by GPS total electron content observation after the 2011 off the Pacific coast of Tohoku Earthquake

“…Their mechanism, however, has not yet been clarified. The sudden TEC depletions in this event were investigated in detail by Saito et al (2011). Chen et al (2011) studied the detail characteristics of the zonally-extended TEC structures (II) which were also observed in Taiwan more than 2,500 km distance from the ionospheric epicenter in the southwest direction.…”

“…This paper and accompanying papers Maruyama et al, 2011;Matsumura et al, 2011;Saito et al, 2011) report all the details of the commencement and evolution of ionospheric disturbances following this earthquake. The ins and outs of post-seismic ionospheric disturbances were first observed by a high-resolution two-dimensional GPS-TEC observation.…”

“…In this paper, we will present an overview of all the ionospheric disturbances and clarify the characteristics of the concentric ionospheric disturbances propagating away from the epicenter. Saito et al (2011) discussed the ionospheric variations in the vicinity of the epicenter. The long-distance propagation of ionospheric waves are discussed by .…”

Localized field-aligned currents and 4-min TEC and ground magnetic oscillations during the 2015 eruption of Chile’s Calbuco volcano

“…After volcanic eruption (e.g., Heki 2006;Dautermann et al 2009) or massive tornado (e.g., Nishioka et al 2013), disturbances in total electron content (TEC) have been observed. After great earthquakes, short-period magnetic and atmospheric pressure oscillations (e.g., Iyemori et al 2005Iyemori et al , 2013 or TEC variations (e.g., Otsuka et al 2006;Saito et al 2011) were observed. As to the theoretical study, TEC oscillations observed after the 2011 off the Pacific coast of Tohoku Earthquake and FACs in the ionosphere generated by acoustic mode waves were well reproduced with numerical simulations by Matsumura et al (2011) and by Zettergren and Snively (2013), respectively.…”

Dynamics of vertical ionospheric inhomogeneities over Irkutsk during 06:00–06:20UT 11/03/2011 caused by Tohoku earthquake

“…Ionospheric effects of the Tohoku earthquake are currently the subject of many papers. Above all, it is papers analyzing data from dense networks of GPS-receivers, located on the Asian territory (Akhoondzadeh, 2012;Kakinami et al, 2011;Astafyeva et al, 2013;Hao et al, 2012;Komjathy et al, 2012;Liu, 2012;Occhipinti et al, 2011;Ogawa et al, 2012;Ouzounov et al, 2011;Saito et al, 2011;Tsugawa et al, 2011) and data from the SuperDARN radar, located on the Hokkaido island (Nishitani et al, 2011;Ogawa et al, 2012). These instruments have the best temporal resolution -from several seconds to 2 minutes, enabling to monitor the highly dynamic processes.…”