Ionospheric Detection of Natural Hazards

Abstract

Natural hazards (NH), such as earthquakes, tsunamis, volcanic eruptions, and severe tropospheric weather events, generate acoustic and gravity waves that propagate upward and cause perturbations in the atmosphere and ionosphere. The first NH-related ionospheric disturbances were detected after the great 1964 Alaskan earthquake by ionosondes and Doppler sounders. Since then, many other observations confirmed the responsiveness of the ionosphere to NH. Within the last two decades, outstanding progress has been made in this area owing to the development of networks of ground-based dual-frequency Global Navigation Satellite Systems (GNSS) receivers. The use of GNSS-sounding has substantially enlarged our knowledge about the solid earth/ocean/atmosphere/ionosphere coupling and NH-related ionospheric disturbances and their main features. Moreover, recent results have demonstrated that it is possible to localize NH from their ionospheric signatures and also, if/when applicable, to obtain the information about the NH source (i.e., the source location and extension and the source onset time). Although all these results were obtained in retrospective studies, they have opened an exciting possibility for future ionosphere-based detection and monitoring of NH in near-real time. This article reviews the recent developments in the area of ionospheric detection of earthquakes, tsunamis, and volcanic eruptions, and it discusses the future perspectives for this novel discipline. Plain Language SummaryThe ionosphere is the ionized region of the Earth's atmosphere that is located between~60 and~800 km of altitude. The ionosphere is largely impacted by the solar and magnetic activities, as well as by the neutral atmosphere. Besides these large-scale and global processes influencing from above, the ionosphere can be more "locally" perturbed from below by geophysical phenomena (e.g., earthquakes, tsunamis, volcanic eruptions, and severe tropospheric weather events) and by man-made events (e.g., explosions, rocket and missile launches, and mine blasts). From below, the disturbances arrive in the ionosphere as acoustic and gravity waves. Upon their upward propagation, these waves grow in amplitude up to a million times owing to the exponential decrease of the atmospheric density with height. Consequently, the acoustic and gravity waves generated at the Earth's surface may provoke significant perturbations in the upper atmosphere and ionosphere. In the ionosphere, the perturbations can be detected by ionospheric sounding tools, such as GNSS receivers, ionosondes, and airglow cameras.

Investigation of Ionospheric Response to June 2009 Sarychev Peak Volcano Eruption

“…The main theoretical aspects of GNSS application to ionosphere sounding are widely known and can be found in a number of publications (see, for example, papers [21][22][23] and references in them). In this work we adopted a classical approach to TEC data analysis, assuming that all TEC variations occur in a thin F2-layer of maximum ionization [24] (the shell model [1]).…”

“…According to special studies (see, for example, [1,29]) and a great number of researchworks investigating ionospheric response to different natural and man-made phenomena (see, for example, references in publication [22]) errors of differential TEC estimates obtained by using dual-frequency phase GNSS-measurements do not exceed 0.01-0.02 TECU. As can be seen from the following illustrations (see the next section) the typical noise level of our filtered TEC series do not exceed 0.02 TECU.…”

Large air pressure changes triggered by P-SV ground motion in a cave in northern Taiwan

“…Previous studies (Liu et al, 2006(Liu et al, , 2011a(Liu et al, , 2011b(Liu et al, , 2019Otsuka et al, 2009;Astafyeva et al, 2011;Sun et al, 2011Sun et al, , 2016Astafyeva, 2019;Chou et al, 2020) reported that acoustic wavs can propagate from the ground upward the atmosphere and drives changes in electron density in the ionosphere.…”

Meteorological Storm Influence on the Ionosphere Parameters

“…The sources of such waves in the lower atmosphere are diverse. For example, they include mesoscale turbulence and convection [32][33][34][35], mesoscale disturbances arising in the atmosphere when a stationary incoming stream flows around mountains (the so called orography effects) [36,37], earthquakes [38][39][40], the passage of the solar terminator and solar eclipse [41][42][43][44][45], meteorological disturbances, and typhoons [46][47][48][49][50][51][52][53][54][55]. In numerous theoretical studies, the generation, propagation, and influence of AGWs have been studied in sufficient detail [56][57][58].…”