Ionosonde tracking of infrasound wavefronts in the thermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake

Abstract

Ionospheric disturbances associated with the M8.8 Chile earthquake (35.91°S, 72.73°W) on 27 February 2010 were observed at Kazan, Russia (55.85°N, 48.81°E). Rapid‐run ionograms at 1 min intervals exhibited multiple‐cusp signatures (MCSs) for more than 30 min, which have been observed several times after large earthquakes. The ionospheric disturbances were caused by infrasound propagating upward in the atmosphere, which modified the electron density distribution through ion‐neutral collisions. The anomaly of the vertical electron density distribution responsible for the MCSs was analyzed by converting the ionogram traces into real height profiles. The density profiles at 1 min intervals allowed the tracking of the vertical propagation of infrasound and provided information on parameters of acoustic waves, which was not possible from the previous measurements such as standard ionograms at 5–15 min intervals, HF Doppler soundings, and total electron content using satellite beacon signals. The speed of acoustic waves in the thermosphere was evaluated from the consecutive ionograms with MCSs, and it was found that the thermospheric temperature was slightly higher than that calculated using the Mass Spectrometer and Incoherent Scatter Radar empirical model (NRLMSISE‐00).

Interpretation of deformed ionograms induced by vertical ground motion of seismic Rayleigh waves and infrasound in the thermosphere

“…(Maruyama et al, 2016). The difference between the epicentral distances for Obninsk and Kazan was approximately 773 km.…”

Ionospheric F2-layer Perturbations Observed After the M8.8 Chile Earthquake on February 27, 2010, at Long Distance from the Epicenter

“…Rayleigh wave signatures in the ionosphere following earthquakes have been measured by Doppler sounding (e.g., Yuen et al 1969;Tanaka et al 1984;Artru et al 2004;Chum et al 2016) using TEC measurements (e.g., Ducic et al 2003;Astafyeva et al 2009;Rolland et al 2011) and the inspection of ionograms (Maruyama et al 2012(Maruyama et al , 2016a(Maruyama et al , 2016b.…”

Automatic estimation of dynamics of ionospheric disturbances with 1–15 minute lifetimes as derived from ISTP SB RAS fast chirp ionosonde data

“…The increased temporal resolution of the ionosonde allows us to consider the background ionosphere at the averaging period to be stationary and to persistently find tracks of 1-15 min ionospheric irregularities on ionograms. Using the proposed method and data from the ISTP SB RAS fast chirp ionosonde, located near Irkutsk [Podlesny, 2017;Naumenko, Podlesny, 2017], we have obtained the statistics of the distribution of irregularities by observed velocities for a given region; we have shown that there is an appreciable number of 1-15 min irregularities moving downward with a characteristic observed vertical velocity of ~160 m/s, which in the first approximation does not depend on season.…”

“…These irregularities are sometimes associated with acoustic waves from various powerful sources and can propagate from a source both horizontally [Berngardt et al, 2015a] and vertically [Maruyama et al, 2016a[Maruyama et al, , 2016bBerngardt et al, 2015bBerngardt et al, , 2017.…”

“…Regular 15-min modes of operation of the worldwide network of ionosondes have been put into operation; networks of ionosondes of different types both with pulsed [Reinisch et al, 2009] and with continuous transmitted signals (see, e.g., [Ponyatov et al, 1999;Uryadov et al, 2004] and references therein) have been created. Long-term ionosonde measurements form a basis for the development of modern ionospheric plasma models at heights below the F2-layer maximum and are used for constructing models, which are corrected in real time [Bilitza et al, 2017;Pignalberi et al, 2018], as well as for selective [Liu et al, 2011;Maruyama et al, 2011Maruyama et al, , 2016aMaruyama et al, , 2016bBerngardt et al, 2015b] and statistical studies of ionospheric irregularities [Kurkin et al, 2014;Berngardt et al, 2017;Givishvili, Leshchenko, 2017].…”