On 15 January 2022, the Hunga Tonga‐Hunga Ha’apai submarine volcano erupted violently and triggered a giant atmospheric shock wave and tsunami. The exact mechanism of this extraordinary eruptive ...event, its size and magnitude are not well understood yet. In this work, we analyze data from the nearest ground‐based receivers of Global Navigation Satellite System to explore the ionospheric total electron content (TEC) response to this event. We show that the ionospheric response consists of a giant TEC increase followed by a strong long‐lasting depletion. We observe that the explosive event of 15 January 2022 began at 04:05:54UT and consisted of at least five explosions. Based on the ionospheric TEC data, we estimate the energy released during the main major explosion to be between 9 and 37 Megatons in trinitrotoluene equivalent. This is the first detailed analysis of the eruption sequence scenario and the timeline from ionospheric TEC observations.
Plain Language Summary
On 15 January 2022, the giant explosion of the Hunga Tonga‐Hunga Ha’apai volcano shook the atmosphere of the Earth and generated a tsunami. The exact mechanism and timing of the eruption are not well understood yet, nor is the series of events that occurred directly following the first event. Many scientists are trying to understand the chronology of the eruption using different types of data. Here we investigate the signature of the eruption as recorded in Earth’s ionosphere, the electrically conductive layer of the atmosphere from about 85 to 800 km of altitude. We observe variations in the total electron content (TEC) of the ionosphere using Global Navigation Satellite System receivers (commonly known as GPS receivers). Variations in the TEC through time and space are caused by sound waves from the eruption traveling through the ionosphere. We use these variations to constrain the timing of the eruptive events, identifying at least five major explosions during this eruption. In addition, we use the amplitude of TEC variations to estimate that the largest explosion released energy of about 9–37 Megaton in trinitrotoluene equivalent. This is the first detailed analysis of the eruption scenario and the timeline from ionospheric TEC observations.
Key Points
Ionospheric total electron content (TEC) data reveal that the 15 January 2022 Hunga Tonga volcanic eruption involved at least five large explosions between 4 and 5UT
From TEC observations, we estimate the onset time to be 04:05:54UT and the main explosion energy release of 9–37 Megatons trinitrotoluene equivalent
The eruption‐driven shock wave caused an unprecedentedly strong and long‐lasting depletion in the ionosphere
We investigate the oceanic and ionospheric response in New Caledonia‐New Zealand and Chile‐Argentina to the 15 January 2022 Hunga‐Tonga volcanic eruption. For the first time, we highlight a reversed ...response in the oceans and in the ionosphere in terms of the amplitudes. The sea‐surface fluctuations due to the passage of the atmospheric Lamb wave (i.e., air‐sea wave) were not remarkable while the related ionospheric perturbation was considerable. Reversely, the eruption‐induced tsunami (“regular” tsunami) caused major variations in sea‐surface heights (∼1 m near the volcano and ∼2 m along the Chilean coastline), whereas the associated ionospheric perturbation was quite small. The observed large‐amplitude ionospheric response due to Lamb waves propagation is difficult to explain, and the coupling between the Lamb wave and the ionosphere is not well‐understood yet. For the first time, we estimate the delay between the Lamb waves and their signatures in the ionosphere to be ∼12–20 min.
Plain Language Summary
The eruption of Hunga‐Tonga volcano produced a variety of atmospheric and tsunami waves recorded all over the world. We study the impacts of the eruption together on the oceans and in the ionosphere in New Caledonia‐New Zealand (near the volcano) and Chile‐Argentina (far from the volcano). At the sea surface, we observe two phenomena causing sea‐height variations. The first is a small tsunami (air‐sea wave) created by the Lamb wave: the high‐pressure atmospheric wave triggered by the eruption. The second is the tsunami induced by the eruption itself. Spectacularly, at 300 km altitude, in the ionosphere, we observe perturbations in the electron content caused by the Lamb wave and by the regular tsunami. We are the first to report on the reversed amplitude of the two phenomena in the oceans and in the ionosphere. The sea‐surface perturbation caused by the Lamb wave was not significant, while ionospheric perturbation was considerable. In contrast, the regular tsunami wave produced major variations. For the first time, we estimate the time delay between the Lamb wave and its signature in the ionosphere.
Key Points
Joint study of oceanic and ionospheric response in New Caledonia‐New Zealand and Chile‐Argentina to the 15 January 2022 volcanic eruption
Near‐surface propagating Lamb wave caused a small tsunami in the ocean (air‐sea wave) and unusually strong disturbances in the ionosphere
Inversely, the eruption‐generated tsunami showed significant wave heights in the ocean and much smaller response in the ionosphere
On the 21 August 2017 the eclipse shadow drastically changed the state of the ionosphere over the United States. This effect on the ionosphere is visible in the total electron content measured by ...Global Navigation Satellite Systems (GNSS). The shadow moved with the supersonic speed of ~1,000 m/s over Oregon to ~650 m/s over South Carolina. In order to exhaustively explore the ionospheric signature of the eclipse, we use data of total electron content from ~3,000 GNSS stations seeing multiple Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) satellites to visualize the phenomena. This tremendous dataset allows high‐resolution characterization of the frequency content and wavelengths—using an omega‐k analysis based on 3‐D fast Fourier transform—of the eclipse signature in the ionosphere in order to fully identify traveling ionospheric disturbances (TIDs). We confirm the generation of TIDs associated with the eclipse including TIDs interpreted as bow waves in previous studies. Additionally, we reveal, for the first time, short (50–100 km) and long (500–600 km) wavelength TIDs with periods between 30 and 65 min. The sources of the revealed short wavelength TIDs are co‐located with the regions of stronger gradient of the EUV related to sunspots. Our work confirms and describes physical properties of the waves observable in the ionosphere during the Great American Eclipse.
Plain Language Summary
A total solar eclipse occurred on 21 August 2017 over the United States with the eclipse shadow reaching supersonic speed. We calculate the differential total electron content to visualize the evolution of the phenomena with incredible high spatial and temporal resolution. Traveling ionospheric disturbances associated with the eclipse with a period of up to 1 hr and wavelengths of 40 to 600 km including bow waves with a period of ~25 min and wavelength of ~300 km are identified using an omega‐k analysis based on 3‐D fast Fourier transform. The additionally highlighted shortest (50–100 km) and longest (500–600 km) wavelength traveling ionospheric disturbances have not been observed before. The shortest waves seem to be related to sunspots.
Key Points
GNSS observations of solar eclipse show differential total electron content (dTEC) depletions reaching −0.4TECU in the path of totality
We observe longer wavelength TIDs that are related to the TEC depletion due to the Moon's shadow, as well as shorter wavelength TIDs
The omega‐k analysis using 3‐D FFT allows to highlight the characteristics of the main and more energetic generated TIDs and bow waves.
Although only centimeters in amplitude over the open ocean, tsunamis can generate appreciable wave amplitudes in the upper atmosphere, including the naturally occurring chemiluminescent airglow ...layers, due to the exponential decrease in density with altitude. Here, we present the first observation of the airglow tsunami signature, resulting from the 11 March 2011 Tohoku earthquake off the eastern coast of Japan. These images are taken using a wide‐angle camera system located at the top of the Haleakala Volcano on Maui, Hawaii. They are correlated with GPS measurements of the total electron content from Hawaii GPS stations and the Jason‐1 satellite. We find waves propagating in the airglow layer from the direction of the earthquake epicenter with a velocity that matches that of the ocean tsunami. The first ionospheric signature precedes the modeled ocean tsunami generated by the main shock by approximately one hour. These results demonstrate the utility of monitoring the Earth's airglow layers for tsunami detection and early warning.
Key Points
Coupling of the ocean surface to the upper atmosphere enables tsunami imaging
The first ionospheric signature precedes the modeled ocean tsunami by one hour
Summary
Tsunamis propagating along the ocean surface generate internal gravity waves which can be detected in the atmosphere and ionosphere using airglow or total electron content (TEC) measurements. ...Since the late 1960s, the summation of the seismic normal modes of the Earth allows to simulate the seismic ground motions measured by seismometers. We present a detailed case study of the same technique extended to the whole solid Earth–ocean–atmosphere system and show how the extended normal modes can be used to retrieve the tsunami signature not only in the ocean but also in the atmosphere and the ionosphere. On the example of the tsunami triggered by the 2012 M
w = 7.8 Haida Gwaii earthquake, we illustrate the coupling mechanisms under play and investigate in details the propagation properties of Lamb modes, atmospheric gravity modes and tsunami modes. The computed normal modes show a resonance between the tsunami modes and the atmospheric gravity modes at specific frequencies: 1.5, 2 and 2.5 mHz. We highlight that only the 1.5 mHz resonance of the tsunami modes can survive up to the ionospheric heights. Other remarkable features are also presented, such as the arrival of fundamental mode gravity waves prior to the (extended in the atmosphere) tsunami wave and the increased ocean/atmosphere coupling efficiency for larger ocean depths and during daytime. At last, for the purpose of validating the technique, we apply it to three real tsunami events and evaluate how well we quantitatively reconstruct the main features of the sea level anomaly measured by Deep-ocean Assessment and Reporting of Tsunamis buoys and the global positioning system (GPS)-derived TEC perturbation.
Following the first‐time ionospheric imaging of a seismic fault, here we perform a case study on retrieval of parameters of the extended seismic source ruptured during the great M9.0 Tohoku‐oki ...earthquake. Using 1 Hz ionospheric GPS data from the Japanese network of GPS receivers (GEONET) and several GPS satellites, we analyze spatiotemporal characteristics of coseismic ionospheric perturbations and we obtain information on the dimensions and location of the sea surface uplift (seismic source). We further assess the criterion for the successful determination of seismic parameters from the ionosphere: the detection is possible when the line of sights from satellites to receivers cross the ionosphere above the seismic fault region. Besides, we demonstrate that the multisegment structure of the seismic fault of the Tohoku‐oki earthquake can be seen in high‐rate ionospheric GPS data. Overall, our results show that, under certain conditions, ionospheric GPS‐derived TEC measurements could complement the currently working systems, or independent ionospherically based system might be developed in the future.
Key Points
Parameters of seismic source can be deduced from 1Hz ionospheric GPS data
Ionosphere can visualize a multi‐segment structure of a seismic fault
CID velocity ~1.4 km/s points on either shock waves, or acoustic waves in water
Following the first-time ionospheric imaging of a seismic fault, here we perform a case study on retrieval of parameters of the extended seismic source ruptured during the great M9.0 Tohoku-oki ...earthquake. Using 1Hz ionospheric GPS data from the Japanese network of GPS receivers (GEONET) and several GPS satellites, we analyze spatiotemporal characteristics of coseismic ionospheric perturbations and we obtain information on the dimensions and location of the sea surface uplift (seismic source). We further assess the criterion for the successful determination of seismic parameters from the ionosphere: the detection is possible when the line of sights from satellites to receivers cross the ionosphere above the seismic fault region. Besides, we demonstrate that the multisegment structure of the seismic fault of the Tohoku-oki earthquake can be seen in high-rate ionospheric GPS data. Overall, our results show that, under certain conditions, ionospheric GPS-derived TEC measurements could complement the currently working systems, or independent ionospherically based system might be developed in the future. Key Points Parameters of seismic source can be deduced from 1Hz ionospheric GPS data Ionosphere can visualize a multi-segment structure of a seismic fault CID velocity ~1.4 km/s points on either shock waves, or acoustic waves in water
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