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Wavelet coherence spectrum for five days centered on day 145, which is the date of the 2009 North Korean underground nuclear explosion. The dominant frequencies in a band from 0.0035 to 0.0078 Hz at the time of the detonation (reproduction of Figure 1 in Yang et al., 2012).
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The ionospheric response to explosions which occur at or below the Earth's surface has been noted since the first detonations of nuclear devices during the early period of aboveground testing. Acoustic gravity waves and traveling ionospheric disturbances were detected in association with test explosions carried out by the Union of Soviet Socialist...
Citations
... Phenomena such as earthquakes, meteor air bursts, nuclear blasts, tsunamis, and volcanic eruptions can trigger traveling disturbances in the atmosphere that can be detected around the world (Calais and Minster 1998;Astafyeva 2019;Afraimovich et al. 2001Afraimovich et al. , 2013Artru et al. 2005;Azeem et al. 2017;Huang et al. 2019). The Hunga Tonga-Hunga Ha'apai underwater volcano (20.53° S 175.38° W UT+13) erupted 5 times during the period corresponding to 15 January 2022 from 04:05 UT and 04:54 UT ). ...
The eruption of the Hunga Tonga Hunga Ha’apai volcano on 15 January 2022 significantly impacted the lower and upper atmosphere globally. Using multi-instrument observations, we described disturbances from the sea surface to the ionosphere associated with atmospheric waves generated by the volcanic eruption. Perturbations were detected in atmospheric pressure, horizontal magnetic field, equatorial electrojet (EEJ), ionospheric plasma drifts, total electron content (TEC), mesospheric and lower thermospheric (MLT) neutral winds, and ionospheric virtual height measured at low magnetic latitudes in the western South American sector (mainly in Peru). The eastward Lamb wave propagation was observed at the Jicamarca Radio Observatory on the day of the eruption at 13:50 UT and on its way back from the antipodal point (westward) on the next day at 07:05 UT. Perturbations in the horizontal component of the magnetic field (indicative of EEJ variations) were detected between 12:00 and 22:00 UT. During the same period, GNSS-TEC measurements of traveling ionospheric disturbances (TIDs) coincided approximately with the arrival time of Lamb and tsunami waves. On the other hand, a large westward variation of MLT winds occurred near 18:00 UT over Peru. However, MLT perturbations due to possible westward waves from the antipode have not been identified. In addition, daytime vertical plasma drifts showed an unusual downward behavior between 12:00 and 16:00 UT, followed by an upward enhancement between 16:00 and 19:00 UT. Untypical daytime eastward zonal plasma drifts were observed when westward drifts were expected. Variations in the EEJ are highly correlated with perturbations in the vertical plasma drift exhibiting a counter-equatorial electrojet (CEEJ) between 12:00 and 16:00 UT. These observations of plasma drifts and EEJ are, so far, the only ground-based radar measurements of these parameters in the western South American region after the eruption. We attributed the ion drift and EEJ perturbations to large-scale thermospheric wind variations produced by the eruption, which altered the dynamo electric field in the Hall and Pedersen regions. These types of multiple and simultaneous observations can contribute to advancing our understanding of the ionospheric processes associated with natural hazard events and the interaction with lower atmospheric layers.
Graphical Abstract
... Natural hazards such as volcanic eruptions, earthquakes, and tsunamis can perturb the ionosphere (Astafyeva 2019;Huang et al. 2019;Calais and Minster 1995;Peltier and Hines 1976;Hargreaves 1992;Occhipinti 2015;Rolland et al. 2010;Meng et al. 2019;Artru et al. 2005;Chou et al. 2017;Zettergren et al. 2017). In detail, these events can generate acoustic and gravity waves (AGWs), that are amplified as atmosphere density decreases and can reach the ionosphere. ...
Earthquakes and tsunamis can trigger acoustic and gravity waves that could reach the ionosphere, generating electron density disturbances, known as traveling ionospheric disturbances. These perturbations can be investigated as variations in ionospheric total electron content (TEC) estimated through global navigation satellite systems (GNSS) receivers. The VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithm is a well-known real-time tool for estimating TEC variations. In this context, the high amount of data allows the exploration of a VARION-based machine learning classification approach for TEC perturbation detection. For this purpose, we analyzed the 2015 Illapel earthquake and tsunami for its strength and high impact. We use the VARION-generated observations (i.e., dsTEC/dt) provided by 115 GNSS stations as input features for the machine learning algorithms, namely, Random Forest and XGBoost. We manually label time frames of TEC perturbations as the target variable. We consider two elevation cut-off time series, namely, 15° and 25°, to which we apply the classifier. XGBoost with a 15° elevation cut-off dsTEC/dt time series reaches the best performance, achieving an F1 score of 0.77, recall of 0.74, and precision of 0.80 on the test data. Furthermore, XGBoost presents an average difference between the labeled and predicted middle epochs of TEC perturbation of 75 s. Finally, the model could be seamlessly integrated into a real-time early warning system, due to its low computational time. This work demonstrates high-probability TEC signature detection by machine learning for earthquakes and tsunamis, that can be used to enhance tsunami early warning systems.
... They cannot propagate vertically but in the oblique direction with a much slower sound speed. The direction of the group velocity is perpendicular to that of the phase velocity in the vertical direction (Hines 1960;Huang et al. 2019). Because of the slow speed, the travel time of gravity waves with a period of 10-15 min and horizontal phase velocity of 200-310 m/s from the ground to the ionosphere is estimated as 45-60 min (Astafyeva 2019). ...
The Hunga Tonga–Hunga Ha’apai (HTHH) undersea volcanic eruption that occurred at 04:15 UT on 15 January 2022 is one of the most explosive events in the modern era, and a vertical plume reached approximately 55 km, corresponding to a height of the lower mesosphere. The intense explosion and subsequent plume generated acoustic and atmospheric gravity waves detected by ground-based instruments worldwide. Because a global-scale atmospheric and ionospheric response to the large volcanic eruption has not yet been observed, it provides a unique opportunity to promote interdisciplinary studies of coupling processes in lithosphere–atmosphere–ionosphere with ground-based and satellite observations and modeling. Further, this event allows us to elucidate the propagation and occurrence features of traveling ionospheric disturbances, the generation of equatorial plasma bubbles, the cause of electron density holes around the volcano, and the magnetic conjugacy of magnetic field perturbations. The most notable point among these studies is that the medium-scale travelling traveling ionospheric disturbances (MSTIDs) have magnetic conjugacy even in the daytime ionosphere and are generated by an external electric field, such as an E-region dynamo field, due to the motions of neutrals in the thermosphere. This advocates a new generation mechanism of MSTIDs other than the neutral oscillation associated with atmospheric gravity waves and electrified MSTIDs, which are frequently observed during daytime and nighttime, respectively. This paper reviews the recent studies of atmospheric and ionospheric disturbances after the HTHH volcanic eruption and summarizes what we know from this extreme event analysis. Further, we analyzed new datasets not shown in previous studies to give some new insights to understanding of some related phenomena. As a result, we also found that 4-min plasma flow oscillations caused by the acoustic resonance appeared with the amplitude of approximately 30 m/s in the northern hemisphere a few hours before the initial arrival of the air pressure waves. The propagation direction was westward, which is the same as that of the daytime MSTIDs with a magnetic conjugate feature. This result suggests that the 4-min oscillations are generated by an external electric field transmitted to the northern hemisphere along magnetic field lines.
Graphical Abstract
... The blast progression had also been analyzed using still frames and images from video surveillance footage overlooking the port (Diaz, 2021). With such approach, numerical fit for the size of the expanding fireball as a function of time provided an estimated energy yield of 0.6 kilotons of 20 TNT equivalent. Meanwhile, analysis of videos that were posted on social media produced an estimate of explosion strength between 0.5-1.12 ...
A major explosion happened in Beirut on 4 August 2020, releasing a significant amount of energy into the atmosphere. The energy released may have reached the upper atmosphere and generated some traveling ionospheric disturbances (TIDs), which may affect radio wave propagation. In this study, we used data from the Defense Meteorological Satellite Program (DMSP) and ground-based ionosondes in the Mediterranean region to investigate the ionospheric response to this historic explosion event. Our DMSP data analysis revealed a noticeable increase in the ionospheric electron density near Beirut area following the explosion, accompanied by some wavelike disturbances. Some characteristic TID signatures were also identified in the shape of ionogram traces at several locations in the Mediterranean. This event occurred during a period of relatively quiet geomagnetic conditions, making the observed TIDs likely to originate from the Beirut explosion, and not from other sources such as auroral activities. These observational findings demonstrate that TIDs from the Beirut explosion were able to propagate over longer distance beyond the immediate areas of Lebanon and Israel/Palestine, reaching the Mediterranean and Eastern Europe.
... We performed a wavelet transform to analyze the spectrogram associated with the TEC time series in 4 nearfield GPS sites within the first 2 h after the eruption. As shown in Figure 4a-4d, considering PRN23 as an example, the spectrogram clearly shows the energy centered at 3-4 mHz, which is consistent with the fact that fluctuations in the atmosphere above the acoustic cutoff frequency (~3.3 mHz) are commonly coupled in the acoustic mode (Shults et al., 2016;Astafyeva, 2019;Huang et al., 2019;Lin et al., 2022). Synthesizing the characteristics of the arrival time and travel speed of the disturbance in the near-field, the spectrogram further verifies that the near-field ionospheric anomalies were mainly related to the acoustic shock wave caused by the volcanic explosion from the lower atmosphere to the ionosphere. ...
Hunga Tonga-Hunga Ha’apai climactic eruption on January 15, 2022, released enormous energy that affected the ionosphere over the Pacific Rim. We analyzed ionospheric disturbance following volcanic eruptions using near-field (<1000km), regional (1000–5000 km), and far-field (5000–12000 km) global positioning system (GPS) observations. The results indicate that the near-field ionospheric perturbation that occurred 8–15 min after the cataclysmic eruption was mainly derived from the shock wave (~1000 m/s) generated by the blast, while the low-frequency branch with long-distance propagation characteristics over the regional and the far-field was mainly associated with atmospheric Lamb waves (~330 m/s). Moreover, the amplitude of disturbance and background total electron content (TEC) are related proportionally. The intensity of the volcanic eruption and the background ionospheric conditions determine the magnitude of ionospheric responses. TEC perturbations were invisible on the reference days. Furthermore, the source location and onset time were calculated using the ray tracing technique, which confirms that the Tonga event triggered the ionospheric anomaly beyond the crater. Finally, the change in the frequency of the perturbations coincided with the arrival of the initial tsunami, implying the generation of a meteotsunami.
... Atmospheric waves, produced by energetic events at the Earth's surface, underground, or in the atmosphere, can propagate up to the thermosphere/ionosphere and couple with ionospheric plasma (Astafyeva, 2019;Huang et al., 2019;Meng et al., 2019). Propagation to these heights is advantageous as the free electrons in the ionosphere are an easy target for radio frequency (RF) remote sensing. ...
Earth's ionosphere has long been targeted as a medium for remote sensing of explosive terrestrial events such as earthquakes, volcanic eruptions, and nuclear/conventional weapon detonations. Until now, the only confirmed ionospheric detections have been of very large events that were easily detectable through other traditional global sensor systems (e.g., seismic). We present the first clear, confirmed detections of relatively low yield 1‐ton TNT‐equivalent chemical explosions using pulsed Doppler radar observations of isodensity layers in the ionospheric E region. The shape and spectra of the detected waveforms closely match predictions from the acoustic ray tracing and weakly nonlinear waveform propagation models. The explosions were roughly three orders of magnitude lower yield than any previous confirmed ionospheric detection and represent the first conclusive evidence that explosions of this size can have clear impacts on the ionosphere. This technique could improve the remote detection of both anthropogenic and natural explosive events.
... Some other factors also result in ionospheric anomalies in the short term, for example, nuclear explosions [9][10][11][12] and rocket launching [13,14]. Thanks to an increasing number of continuous GNSS stations, the research stream that has been attractive to scientists for almost two decades is TEC anomalies associated with seismic activities [15][16][17][18][19]. Determination of the TEC disturbances related to seismic events applies different methods and monitoring instruments. ...
Total Electron Content (TEC) is the integral of the electron density along the path between receivers and satellites. TEC measured from Global Navigation Satellite Systems (GNSS) data is valuable to monitor space weather and correct ionospheric models. TEC noise detection is also an essential channel to forecast space weather and research the relationship between the atmosphere and natural phenomena like geomagnetic storms, earthquakes, volcanos, and tsunamis. In this study, we apply optimization machine learning techniques and integrated GNSS and solar activity data to determine GNSS-TEC noise at the International GNSS Service (IGS) stations in the Tonga volcanic region. We investigate 38 indices related to the geomagnetic field and solar wind plasma to select the essential parameters for forecast models. The findings show the best-suited parameters to predict vertical TEC time series: plasma temperature (or Plasma speed), proton density, Lyman alpha, R sunspot, Ap index (or Kp, Dst), and F10.7 index. Applying the Ensemble algorithm to build the TEC forecast models at the investigated IGS stations gets the accuracy from 1.01 to 3.17 TECU. The study also shows that machine learning combined with integrated data can provide a robust approach to detecting TEC noise caused by seismic activities.
... While planetary atmospheres naturally filter out high-frequency components, low-frequency acoustic waves (infrasound) and gravity waves are known to travel large distances without significant attenuation (Blackstock, 2000). These waves are now routinely detected from high vantage points on Earth, and even from orbit, in the aftermath of significant anthropogenic and seismic events (Huang et al., 2019). ...
Barometers floating on high‐altitude balloons in the relatively clement cloud layer on Venus could detect and characterize acoustic waves generated by seismic activity, avoiding the need for high‐temperature electronics required for surface seismology. Garcia et al. (2022, https://doi.org/10.1029/2022GL098844) recently demonstrated the detection of low‐frequency sound (infrasound) caused by earthquakes of magnitudes 7.3 and 7.5 from stratospheric balloons nearly 3,000 km away from the epicenter. They provided a preliminary demonstration of earthquake magnitude and location inversion, and the determination of S‐ and Rayleigh wave velocities using only their acoustic signature. Large earthquakes produce low‐frequency seismic waves that penetrate the interiors of planets; their detection at continental‐scale distances from a high‐vantage point demonstrates the feasibility of balloon‐based investigations of Venus' interior. We contextualize these results within the effort to perform seismology on Venus from balloons, discuss its limitations, and share perspectives on open research questions in this area.
... TID signatures were also observed after other explosive events (Huang et al., 2019). In particular nuclear tests have been known to cause ionospheric disturbances (e.g., Breitling & Kupferman, 1967;Hines, 1967;Kanellakos, 1967;Albee & Kanellakos, 1968;Park et al., 2013;Zhang & Tang, 2015). ...
... Some historic events, such as the industrial accident in Flixborough in 1974 (Jones & Spracklen, 1974;Krasnov et al., 2003) and the conventional bombing campaign during World War II (Scott & Major, 2018), have recently been reanalysed from this perspective. However, it has been shown both from observations and from theoretical considerations that the MSTIDs generated through different mechanisms can be very distinct from each other (Kirchengast, 1997;Huang et al., 2019). Clear differences have been observed when comparing disturbances generated from highly localised explosive events such as nuclear explosions and volcanic eruptions (Roberts et al., 1982;Huang et al., 2019). ...
... However, it has been shown both from observations and from theoretical considerations that the MSTIDs generated through different mechanisms can be very distinct from each other (Kirchengast, 1997;Huang et al., 2019). Clear differences have been observed when comparing disturbances generated from highly localised explosive events such as nuclear explosions and volcanic eruptions (Roberts et al., 1982;Huang et al., 2019). Ionospheric signatures of less localised phenomena such as tsunamis and seismic events are even more different (Astafyeva, 2019;Huang et al., 2019). ...
The 15 January 2022 eruption of the Hunga volcano provides a unique opportunity to study the reaction of the ionosphere to large explosive events. In particular, this event allows us to study the global propagation of travelling ionospheric disturbances using various instruments. We focus on the detection of the ionospheric disturbances caused by this eruption over Europe, where dense networks of both ionosondes and GNSS receivers are available. This event took place on the day of a geomagnetic storm. We show how data from different instruments and from different observatories can be combined to clearly distinguish the TIDs produced by the eruption from those caused by concurrent geomagnetic activity. The Lamb wave front was detected as the strongest disturbance in the ionosphere, travelling at between 300 and 340 m/s, consistent with the disturbances in the lower atmosphere. By comparing observations obtained from multiple types of instruments, we also show that TIDs produced by various mechanisms are present simultaneously, with different types of waves affecting different physical quantities. This illustrates the importance of analysing data from multiple independent instruments in order to obtain a full picture of an event like this one, as relying on only a single data source might result in some effects going unobserved.
... group velocities (Artru et al., 2004;Huang et al., 2019). The initial AGWs generated by these events can even reach ionospheric heights with exponentially increased amplitudes, modulating ionospheric electron density and leading to traveling ionospheric disturbances (TIDs) through ion-neutral collisional momentum transfer (e.g., Afraimovich et al., 2010;Cahyadi & Heki, 2013;Chou et al., 2020;Hao et al., 2006;Huba et al., 2015;Inchin et al., 2020;Komjathy et al., 2012;Liu et al., 2006;Nishioka et al., 2013;Rolland et al., 2011;Tsugawa et al., 2011;Zettergren et al., 2017). ...
This paper investigates the local and global ionospheric responses to the 2022 Tonga volcano eruption, using ground‐based Global Navigation Satellite System total electron content (TEC), Swarm in situ plasma density measurements, the Ionospheric Connection Explorer (ICON) Ion Velocity Meter (IVM) data, and ionosonde measurements. The main results are as follows: (a) A significant local ionospheric hole of more than 10 TECU depletion was observed near the epicenter ∼45 min after the eruption, comprising of several cascading TEC decreases and quasi‐periodic oscillations. Such a deep local plasma hole was also observed by space‐borne in situ measurements, with an estimated horizontal radius of 10–15° and persisted for more than 10 hr in ICON‐IVM ion density profiles until local sunrise. (b) Pronounced post‐volcanic evening equatorial plasma bubbles (EPBs) were continuously observed across the wide Asia‐Oceania area after the arrival of volcano‐induced waves; these caused a Ne decrease of 2–3 orders of magnitude at Swarm/ICON altitude between 450 and 575 km, covered wide longitudinal ranges of more than 140°, and lasted around 12 hr. (c) Various acoustic‐gravity wave modes due to volcano eruption were observed by accurate Beidou geostationary orbit (GEO) TEC, and the huge ionospheric hole was mainly caused by intense shock‐acoustic impulses. TEC rate of change index revealed globally propagating ionospheric disturbances at a prevailing Lamb‐wave mode of ∼315 m/s; the large‐scale EPBs could be seeded by acoustic‐gravity resonance and coupling to less‐damped Lamb waves, under a favorable condition of volcano‐induced enhancement of dusktime plasma upward E×B drift and postsunset rise of the equatorial ionospheric F‐layer.
