The Tonga volcano eruption at 04:14:45 UT on 2022-01-15 released enormous amounts of energy into the atmosphere, triggering very significant geophysical variations not only in the immediate proximity of the epicenter but also globally across the whole atmosphere. This study provides a global picture of ionospheric disturbances over an extended period for at least 4 days. We find traveling ionospheric disturbances (TIDs) radially outbound and inbound along entire Great-Circle loci at primary speeds of ∼300–350 m/s (depending on the propagation direction) and 500–1,000 km horizontal wavelength for front shocks, going around the globe for three times, passing six times over the continental US in 100 h since the eruption. TIDs following the shock fronts developed for ∼8 h with 10–30 min predominant periods in near- and far- fields. TID global propagation is consistent with the effect of Lamb waves which travel at the speed of sound. Although these oscillations are often confined to the troposphere, Lamb wave energy is known to leak into the thermosphere through channels such as atmospheric resonance at acoustic and gravity wave frequencies, carrying substantial wave amplitudes at high altitudes. Prevailing Lamb waves have been reported in the literature as atmospheric responses to the gigantic Krakatoa eruption in 1883 and other geohazards. This study provides substantial first evidence of their long-duration imprints up in the global ionosphere. This study was enabled by ionospheric measurements from 5,000+ world-wide Global Navigation Satellite System (GNSS) ground receivers, demonstrating the broad implication of the ionosphere measurement as a sensitive detector for atmospheric waves and geophysical disturbances.

Natural geological disasters such as volcanic eruptions and intense earthquakes can create impulsive forcing near Earth's surface and cause considerable atmospheric pressure waves (e.g., Hines, 1960;Komjathy et al., 2016;Yeh & Liu, 1974). Depending on their velocities and/or frequencies, these atmospheric waves include supersonic shock waves along with acoustic and gravity waves (AGWs). Acoustic waves travel through adiabatic compression and decompression, with frequencies higher than the acoustic cutoff frequency (∼3.3 mHz), periods smaller than 5 min, and radially outward propagating velocity at the sound speed (Astafyeva, 2019;Blanc, 1985). By comparison, gravity waves are triggered by vertical displacement in the ocean surface and atmosphere, with gravity being the predominant restoring force. They are characterized by lower-than-buoyancy frequencies, periods of several to tens of minutes, and obliquely upward propagating pattern with oppositely directed phase and

This paper presents observations of postsunset super plasma bubbles over China and adjacent areas during the second main phase of a storm on 8 September 2017. The signatures of the plasma bubbles can be seen or deduced from (1) deep field‐aligned total electron content depletions embedded in regional ionospheric maps derived from dense Global Navigation Satellite System networks, (2) significant equatorial and midlatitudinal plasma bite‐outs in electron density measurements on board Swarm satellites, and (3) enhancements of ionosonde virtual height and scintillation in local evening associated with strong southward interplanetary magnetic field. The bubbles/depletions covered a broad area mainly within 20°–45°N and 80°–110°E with bifurcated structures and persisted for nearly 5 hr (∼13–18 UT). One prominent feature is that the bubbles extended remarkably along the magnetic field lines in the form of depleted flux tubes, reaching up to midlatitude of around 50°N (magnetic latitude: 45.5°N) that maps to an altitude of 6,600 km over the magnetic equator. The maximum upward drift speed of the bubbles over the magnetic equator was about 700 m/s and gradually decreased with altitude and time. The possible triggering mechanism of the plasma bubbles was estimated to be storm time eastward prompt penetration electric field, while the traveling ionospheric disturbance could play a role in facilitating the latitudinal extension of the depletions.

Postsunset midlatitude traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) were simultaneously observed over American sector during the geomagnetic storm on 8 September 2017. The characteristics of TIDs are analyzed by using a combination of the Millstone Hill incoherent scatter radar data and 2‐D detrended total electron content (TEC) from ground‐based Global Navigation Satellite System receivers. The main results associated with EPBs are as follows: (1) stream‐like structures of TEC depletion occurred simultaneously at geomagnetically conjugate points, (2) poleward extension of the TEC irregularities/depletions along the magnetic field lines, (3) severe equatorial and midlatitude electron density (Ne) bite outs observed by Defense Meteorological Satellite Program and Swarm satellites, and (4) enhancements of ionosphere F layer virtual height and vertical drifts observed by equatorial ionosondes near the EPBs initiation region. The stream‐like TEC depletions reached 46° magnetic latitudes that map to an apex altitude of 6,800 km over the magnetic equator using International Geomagnetic Reference Field. The formation of this extended density depletion structure is suggested to be due to the merging between the altitudinal/latitudinal extension of EPBs driven by strong prompt penetration electric field and midlatitude TIDs. Moreover, the poleward portion of the depletion/irregularity drifted westward and reached the equatorward boundary of the ionospheric main trough. This westward drift occurred at the same time as the sudden expansion of the convection pattern and could be attributed to the strong returning westward flow near the subauroral polarization stream region. Other possible mechanisms for the westward tilt are also discussed.

The Tonga volcano eruption at 04:14:45 UT on 2022-01-15 released enormous amounts of energy into the atmosphere, triggering very significant geophysical variations not only in the immediate proximity of the epicenter but also globally across the whole atmosphere. This study provides a global picture of ionospheric disturbances over an extended period for at least 4 days. We find traveling ionospheric disturbances (TIDs) radially outbound and inbound along entire Great-Circle loci at primary speeds of ~300-350 m/s (depending on the propagation direction) and 500-1,000 km horizontal wavelength for front shocks, going around the globe for three times, passing six times over the continental US in 100 h since the eruption. TIDs following the shock fronts developed for ~8 h with 10-30 min predominant periods in near-and far-fields. TID global propagation is consistent with the effect of Lamb waves which travel at the speed of sound. Although these oscillations are often confined to the troposphere, Lamb wave energy is known to leak into the thermosphere through channels such as atmospheric resonance at acoustic and gravity wave frequencies, carrying substantial wave amplitudes at high altitudes. Prevailing Lamb waves have been reported in the literature as atmospheric responses to the gigantic Krakatoa eruption in 1883 and other geohazards. This study provides substantial first evidence of their long-duration imprints up in the global ionosphere. This study was enabled by ionospheric measurements from 5,000+ world-wide Global Navigation Satellite System (GNSS) ground receivers, demonstrating the broad implication of the ionosphere measurement as a sensitive detector for atmospheric waves and geophysical disturbances.

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The Tonga volcano eruption at 04:14:45 UT on 2022-01-15 released enormous amounts of energy into the atmosphere, triggering very significant geophysical variations not only in the immediate proximity of the epicenter but also globally across the whole atmosphere. This study provides a global picture of ionospheric disturbances over an extended period for at least 4 days. We find traveling ionospheric disturbances (TIDs) radially outbound and inbound along entire Great-Circle loci at primary speeds of ~300-350 m/s (depending on the propagation direction) and 500-1,000 km horizontal wavelength for front shocks, going around the globe for three times, passing six times over the continental US in 100 h since the eruption. TIDs following the shock fronts developed for ~8 h with 10-30 min predominant periods in near-and far-fields. TID global propagation is consistent with the effect of Lamb waves which travel at the speed of sound. Although these oscillations are often confined to the troposphere, Lamb wave energy is known to leak into the thermosphere through channels such as atmospheric resonance at acoustic and gravity wave frequencies, carrying substantial wave amplitudes at high altitudes. Prevailing Lamb waves have been reported in the literature as atmospheric responses to the gigantic Krakatoa eruption in 1883 and other geohazards. This study provides substantial first evidence of their long-duration imprints up in the global ionosphere. This study was enabled by ionospheric measurements from 5,000+ world-wide Global Navigation Satellite System (GNSS) ground receivers, demonstrating the broad implication of the ionosphere measurement as a sensitive detector for atmospheric waves and geophysical disturbances.

This paper presents coordinated and fortuitous ground-based and spaceborne observations of equatorial plasma bubbles (EPBs) over the South American area on 24 October 2018, combining the following measurements: Global-scale Observations of Limb and Disk far ultraviolet emission images, Global Navigation Satellite System total electron content data, Swarm in situ plasma density observations, ionosonde virtual height and drift data, and cloud brightness temperature data. The new observations from the Global-scale Observations of Limb and Disk/ultraviolet imaging spectrograph taken at geostationary orbit provide a unique opportunity to image the evolution of plasma bubbles near the F peak height over a large geographic area from a fixed longitude location. The combined multi-instrument measurements provide a more integrated and comprehensive way to study the morphological structure, development, and seeding mechanism of EPBs. The main results of this study are as follows: (1) The bubbles developed a westward tilted structure with 10-15 • inclination relative to the local geomagnetic field lines, with eastward drift velocity of 80-120 m/s near the magnetic equator that gradually decreased with increasing altitude/latitude. (2) Wave-like oscillations in the bottomside F layer and detrended total electron content were observed, which are probably due to upward propagating atmospheric gravity waves. The wavelength based on the medium-scale traveling ionospheric disturbance signature was consistent with the interbubble distance of ∼500-800 km. (3) The atmospheric gravity waves that originated from tropospheric convective zone are likely to play an important role in seeding the development of this equatorial EPBs event.Plain Language Summary This study presents multi-instrument observations of equatorial plasma density depletions occurred on 24 October 2018 by using Global-scale Observations of Limb and Disk far ultraviolet images, Global Navigation Satellite System total electron content data, electron density measurements from Swarm satellite, ionosonde measurements, and cloud temperature data. This multi-instrument study generated an integrated and detailed image revealing both large-scale and mesoscale structures of the equatorial plasma depletion. Our results also suggest that atmospheric gravity waves originating from tropospheric convection activity could play a significant seeding role in the development of equatorial plasma bubbles. Key Points: • Combined GOLD/UV spectrograph images and ground-based TEC data revealed EPB features and development over a large geographic area • Bottomside F layer oscillations and traveling ionospheric disturbance were observed by ionosonde and detrended TEC results • Atmospheric gravity waves likely play an important role in seeding the R-T instability and the development of this EPB event Correspondence to: E. Aa,