The Earth’s ionosphere is susceptible to disturbances from terrestrial events, including tsunamis, which generate upward-propagating waves. Monitoring these disturbances using signals from global navigation satellites (GNSS) offers a novel way to detect these hazards. The GUARDIAN (GNSS Upper Atmospheric Real-time Disaster Information and Alert Network) System processes real-time satellite data to measure ionospheric changes. We introduce a machine learning-based extension, “Scout”, which implements automated detections for natural hazards. We demonstrate its effectiveness using the July 2025 Mw = 8.8 Kamchatka earthquake and subsequent Pacific-wide tsunami. Crucially, the system detected the ionospheric signature of the incoming tsunami 30 min before it reached the coast of Hawai’i (USA). This result highlights the potential for automated, satellite-based ionospheric monitoring to enhance existing early warning systems by providing crucial additional lead time for life-saving actions.

Abstract Low frequency sound can travel great distances in planetary atmospheres. When these waves reflect off the air/ground interface, energy may be absorbed or transferred to mechanical waves in the subsurface. This study describes the direct and reflected acoustic wave generated by the re‐entry of the OSIRIS‐REx Sample Return Capsule captured on a pair of balloon‐borne recorders. Reflection attenuation at high incidence angles on alluvium deposits are minimal below 10 Hz. Frequency‐dependent ground absorption between 10 and 50 Hz was evident on a low‐floating platform, but masked by atmospheric attenuation and nonlinear wave propagation at higher altitudes. These results bridge the gap between near‐lossless reflection assumed by infrasound studies and frequency‐dependent losses noted in the low audio range.

Sample return capsules (SRCs) entering Earth’s atmosphere at hypervelocity from interplanetary space are a valuable resource for studying meteor phenomena. The 2023 September 24 arrival of the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer SRC provided an unprecedented chance for geophysical observations of a well-characterized source with known parameters, including timing and trajectory. A collaborative effort involving researchers from 16 institutions executed a carefully planned geophysical observational campaign at strategically chosen locations, deploying over 400 ground-based sensors encompassing infrasound, seismic, distributed acoustic sensing, and Global Positioning System technologies. Additionally, balloons equipped with infrasound sensors were launched to capture signals at higher altitudes. This campaign (the largest of its kind so far) yielded a wealth of invaluable data anticipated to fuel scientific inquiry for years to come. The success of the observational campaign is evidenced by the near-universal detection of signals across instruments, both proximal and distal. This paper presents a comprehensive overview of the collective scientific effort, field deployment, and preliminary findings. The early findings have the potential to inform future space missions and terrestrial campaigns, contributing to our understanding of meteoroid interactions with planetary atmospheres. Furthermore, the data set collected during this campaign will improve entry and propagation models and augment the study of atmospheric dynamics and shock phenomena generated by meteoroids and similar sources.

Heliotropes are passive solar hot air balloons that are capable of achieving nearly level flight within the lower stratosphere for several hours. These inexpensive flight platforms enable stratospheric sensing with high-cadence enabled by the low cost to manufacture, but their performance has not yet been assessed systematically. During July to September of 2021, 29 heliotropes were successfully launched from Oklahoma and achieved float altitude as part of the Balloon-based Acoustic Seismology Study (BASS). All of the heliotrope envelopes were nearly identical with only minor variations to the flight line throughout the campaign. Flight data collected during this campaign comprise a large sample to characterize the typical heliotrope flight behavior during launch, ascent, float, and descent. Each flight stage is characterized, dependence on various parameters is quantified, and a discussion of nominal and anomalous flights is provided.

The Jet Propulsion Laboratory (JPL) develops JPL-GIM, a software for generating global ionospheric maps (GIMs) of total electron content (TEC) using measurements from multiple Global Navigation Satellite System (GNSS) constellations. Within this overview paper, we delve into the current state and the most recent enhancements of JPL-GIM. An adaptable Kalman filter provides maps with user-defined temporal and spatial resolutions, while concurrently delivering essential covariance data for uncertainty assessment. Furthermore, multiple shell models offer a versatile framework to balance accuracy and computational efficiency. We present the five operational JPL GIM products (JPLG, JPRG, JPLI, JPLD, JPRT), highlighting JPLG and JPRG, our products routinely delivered to the International GNSS Service (IGS), and introduce a new near-real-time product (JPRT). As an added demonstration of JPL-GIM’s capabilities, we present a very-high-resolution (2-minute, multi-GNSS, 1000-station) configuration to showcase JPL-GIM’s ability to resolve long-lasting effects of the 2022 Hunga Tonga-Hunga Ha’apai eruption. Validations using independent datasets confirm the accurate reproduction of ionospheric variations across all latitudinal bands.

Despite routine detection of coseismic acoustic-gravity waves (AGWs) in Global Navigation Satellite System (GNSS) total electron content (TEC) observations, models of the earthquake-atmosphere-ionosphere dynamics, essential for validating data-driven studies, remain limited. We present the results of three-dimensional numerical simulations encompassing the entire coupling from Earth's interior to the ionosphere during the Mw ${M}_{w}$ 7.8 2016 Kaikoura earthquake. Incorporating the impact of data/model uncertainties in estimating the ionospheric state, the results show a good agreement between observed and simulated slant TEC (sTEC) signals, assessed through a set of metrics. The signals exhibit intricate waveforms, resulting from the integrated nature of TEC and phase cancellation effects, emphasizing the significance of direct signal comparisons along realistic line-of-sight paths. By comparing simulation results initialized with kinematic and dynamic source models, the study demonstrates the quantifiable sensitivity of sTEC to AGW source specifications, pointing to their utility in the analysis of coupled dynamics.

This study explores the intricate relationship between spectral irradiance variations and polar cap mean vertical total electron content (MVTEC) climatology, using ground-based GNSS measure-ments from the Thule station in the Arctic. The analysis focuses on understanding how different solar and magnetospheric processes drive changes in MVTEC patterns over a 2-year period. Three primary factors are identified as key drivers of MVTEC variations: (1) Russell-McPherron Effect: During equinoxes, enhanced energy transfer from the solar wind to the magnetosphere, governed by the Russell-McPherron effect, leads to increased MVTEC variability. This phenomenon arises due to the changing orientation of the solar magnetospheric coordinate system relative to the solar equatorial system, which affects the efficiency of energy deposition in the magnetosphere. As a result, higher ionospheric disturbances are observed during these periods, highlighting the sea-sonal influence of geomagnetic activity on polar cap TEC patterns. (2) Solar Irradiance Variations: The study identifies a strong correlation between fluctuations in solar EUV and F10.7, both proxies for solar irradiance, and the 27-day oscillations in MVTEC, especially during the summer months. These periodic variations are closely tied to the rotational behavior of the sun, suggesting a direct link between solar activity and ionospheric dynamics. The findings emphasize how solar spectral irradiance influences the ionization levels in the polar cap region, with implications for under-standing seasonal and short-term changes in the high-latitude ionosphere. (3) E-Layer Conductivity: Seasonal changes in the E-layer's conductivity also play a crucial role in modulating MVTEC variability. During summer, the presence of a conductive E-layer enhances cross-field plasma diffusion, leading to faster plasma decay and reduced MVTEC fluctuations. In contrast, the winter months are characterized by an insulating E-layer, which slows down plasma decay and allows F-layer structures to persist longer, resulting in increased MVTEC variability. This seasonal dis-parity underscores the importance of the E-layer's physical properties in shaping high-latitude ionospheric behavior. The findings of this study underscore the complex interplay between solar wind activity, solar irradiance, and ionospheric dynamics in shaping the observed patterns of polar cap MVTEC. By revealing the combined effects of solar and geomagnetic processes, this research contributes to a more comprehensive understanding of high-latitude ionospheric variability. Further investigation is needed to fully elucidate the mechanisms behind these interactions, particularly in terms of their implications for space weather forecasting and the operation of navigation systems in polar regions. Enhanced models that incorporate these insights can improve the prediction and mitigation of space weather effects on satellite-based technologies and communication systems.

Balloon-based seismology through the study of low-frequency seismo-acoustic signals (infrasound) has gained acceptance as a viable way to study seismic activity on Venus. Balloon-based barometers have the potential to detect and characterize atmospheric waves launched by venusquakes and volcanic eruptions while offering substantially longer instrument lifetimes in the Venus middle atmosphere, where temperature and pressure are significantly more benign (0–100°C, ∼1 atm) as compared to the surface (>460 °C, ∼90 atm). One of the major challenges in performing balloon-based seismology on Venus is the absence of ground-truth data for event identification and discrimination. To address this challenge, our activities are aimed at building a catalog of terrestrial balloon-recorded infrasound signals of geophysical provenance, using which signal predictions can be extended to Venus and the detectability of events can be analyzed. We will highlight our recently concluded Balloon-based Acoustic Seismology Study (BASS) flight campaign, which served as Earth-analog experiments for Venus balloon-based seismology. Data collected were used to validate seismo-acoustic simulation tools, which are being expanded to include the Venus atmosphere. These tools will used to generate predictions of infrasound signals from geophysical events on Venus. We will also provide perspective on directions for future instrument development for Venus balloon flights.

We study, for the first time, the physical coupling and detectability of meteotsunamis in the earth’s atmosphere. We study the June 13, 2013 event off the US East Coast using Global Navigation Satellite System (GNSS) radio occultation (RO) measurements, Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures, and ground-based GNSS ionospheric total electron content (TEC) observations. Hypothesizing that meteotsunamis also generate gravity waves (GWs), similar to tsunamigenic earthquakes, we use linear GW theory to trace their dynamic coupling in the atmosphere by comparing theory with observations. We find that RO data exhibit distinct stratospheric GW activity at near-field that is captured by SABER data in the mesosphere with increased vertical wavelength. Ground-based GNSS-TEC data also detect a far-field ionospheric response 9 h later, as expected by GW theory. We conclude that RO measurements could increase understanding of meteotsunamis and how they couple with the earth’s atmosphere, augmenting ground-based GNSS TEC observations.

We introduce GUARDIAN, a near-real-time (NRT) ionospheric monitoring software for natural hazards warning. GUARDIAN's ultimate goal is to use NRT total electronic content (TEC) time series to (1) allow users to explore ionospheric TEC perturbations due to natural and anthropogenic events on earth, (2) automatically detect those perturbations, and (3) characterize potential natural hazards. The main goal of GUARDIAN is to provide an augmentation to existing natural hazards early warning systems (EWS). This contribution focuses mainly on objective (1): collecting GNSS measurements in NRT, computing TEC time series, and displaying them on a public website (https://guardian.jpl.nasa.gov). We validate the time series obtained in NRT using well-established post-processing methods. Furthermore, we present an inverse modeling proof of concept to obtain tsunami wave parameters from TEC time series, contributing significantly to objective (3). Note that objectives (2) and (3) are only introduced here as parts of the general architecture, and are not currently operational. In its current implementation, the GUARDIAN system uses more than 70 GNSS ground stations distributed around the Pacific Ring of Fire, and monitoring four GNSS constellations (GPS, Galileo, BDS, and GLONASS). As of today, and to the best of our knowledge, GUARDIAN is the only software available and capable of providing multi-GNSS NRT TEC time series over the Pacific region to the general public and scientific community.

The 15 January 2022 climactic eruption of Hunga volcano, Tonga, produced an explosion in the atmosphere of a size that has not been documented in the modern geophysical record. The event generated a broad range of atmospheric waves observed globally by various ground-based and spaceborne instrumentation networks. Most prominent was the surface-guided Lamb wave (≲0.01 hertz), which we observed propagating for four (plus three antipodal) passages around Earth over 6 days. As measured by the Lamb wave amplitudes, the climactic Hunga explosion was comparable in size to that of the 1883 Krakatau eruption. The Hunga eruption produced remarkable globally detected infrasound (0.01 to 20 hertz), long-range (~10,000 kilometers) audible sound, and ionospheric perturbations. Seismometers worldwide recorded pure seismic and air-to-ground coupled waves. Air-to-sea coupling likely contributed to fast-arriving tsunamis. Here, we highlight exceptional observations of the atmospheric waves.

The Mw8.3 Illapel earthquake on 16 September 2015 induced ionospheric disturbances detected by Global Positioning System ground‐based total electron content (TEC) observations, which display much stronger TEC perturbations above the northern region of the epicenter than above the southern region. To investigate the cause of the asymmetry, we extend the Wave Perturbation—Global Ionosphere‐Thermosphere Model from using a point source representing the epicentral crustal movement to using an extended source including the ground motion caused by propagating seismic waves. The modeling results reveal that on average, 31% of the north‐south asymmetry in the TEC perturbation magnitude is caused by the different ground motion strengths northward and southward of the epicenter, while the remaining 69% is attributed to the background ionospheric state including the magnetic field. In particular, the spatial variation of the background electron density and the magnetic field inclination angle contributes comparably to the north‐south asymmetry.

Introduction: Events on planetary surfaces and atmospheres can generate low frequency sound waves capable of traveling across regional to global scales. These waves carry information not only on the phenomenon that generated them but also the medium through which they passed. Sensitive microbarometers are used to capture these signals on Earth (e. g. the globe-spanning International Monitoring System) and Mars (the InSight lander). However, temperature and pressure conditions on the surface of Venus are inimical to long term sensor deployment, and oceans cover large regions of the Earth. In the last half decade, microbarometers on free flying balloons have emerged as an alternative to surfacebased deployments[1]. This has led to the possibility of monitoring seismic activity on Venus using acoustic waves induced by ground motion captured on balloons floating in the relatively clement cloud deck[2]. However, microbarometers deployed on a single balloon cannot determine signal direction-of-arrival; in particular, there is no practical way to ascertain the azimuth without multiple stations. We are developing the aeroseismometer, a sensor that measures the balloon acceleration induced by impinging sound waves, as an answer to this problem.

The Real-Time Working Group (RTWG) of the International GNSS Service (IGS) is dedicated to providing high-quality data and high-accuracy products for Global Navigation Satellite System (GNSS) positioning, navigation, timing and Earth observations. As one part of real-time products, the IGS combined Real-Time Global Ionosphere Map (RT-GIM) has been generated by the real-time weighting of the RT-GIMs from IGS real-time ionosphere centers including the Chinese Academy of Sciences (CAS), Centre National d'Etudes Spatiales (CNES), Universitat Politècnica de Catalunya (UPC) and Wuhan University (WHU). The performance of global vertical total electron content (VTEC) representation in all of the RT-GIMs has been assessed by VTEC from Jason-3 altimeter for 3 months over oceans and dSTEC-GPS technique with 2 d observations over continental regions. According to the Jason-3 VTEC and dSTEC-GPS assessment, the real-time weighting technique is sensitive to the accuracy of RT-GIMs. Compared with the performance of post-processed rapid global ionosphere maps (GIMs) and IGS combined final GIM (igsg) during the testing period, the accuracy of UPC RT-GIM (after the improvement of the interpolation technique) and IGS combined RT-GIM (IRTG) is equivalent to the rapid GIMs and reaches around 2.7 and 3.0 TECU (TEC unit, 1016 el m−2) over oceans and continental regions, respectively. The accuracy of CAS RT-GIM and CNES RT-GIM is slightly worse than the rapid GIMs, while WHU RT-GIM requires a further upgrade to obtain similar performance. In addition, a strong response to the recent geomagnetic storms has been found in the global electron content (GEC) of IGS RT-GIMs (especially UPC RT-GIM and IGS combined RT-GIM). The IGS RT-GIMs turn out to be reliable sources of real-time global VTEC information and have great potential for real-time applications including range error correction for transionospheric radio signals, the monitoring of space weather, and detection of natural hazards on a global scale. All the IGS combined RT-GIMs generated and analyzed during the testing period are available at https://doi.org/10.5281/zenodo.5042622 (Liu et al., 2021b).

We review observations on the coupling between Earth's surface disturbances and the upper atmosphere. In particular, we focus on the upper atmospheric responses to atmospheric acoustic-gravity waves generated during impulsive surface disturbance events including earthquakes, tsunamis, volcanic eruptions, and explosions. We review the theoretical background for the generation and propagation of atmospheric acoustic-gravity waves from surface disturbance events as well as of the ionospheric plasma response to such acoustic-gravity waves. We review a variety of observational techniques that have been successfully utilized to detect upper atmospheric perturbations induced by surface disturbances and summarize the state-of-the-art knowledge on the coupling processes learnt from these observations. Finally, we touch on some most recent advances in the field and propose directions for future research. Plain Language Summary Earthquakes, tsunamis, volcanic eruptions, and chemical and nuclear explosions on or under the ground create sudden and violent motions of the ground or ocean surface. While ground shakings during some massive earthquakes can be felt by people who live thousands of kilometers away from the epicenters, the shakings can also be detected from the atmosphere hundreds of kilometers above the ground (upper atmosphere). Similarly, tsunamis, volcanic eruptions, and explosions can have footprints in the upper atmosphere as well. These footprints have been successfully detected by a variety of observational techniques. This paper reviews the observational results and the current understanding of the physical mechanisms behind the coupling between the ground/ocean and the upper atmosphere. In addition, future research directions are proposed in order to address the open questions.

We assess the detection of the August 4, 2020 chemical explosion in Beirut, Lebanon (33°N, 35°E). We use ionospheric total electron content (TEC) observations from a regional network of ground‐based Global Positioning System (GPS) receivers to study the ionospheric variability and wave perturbations generated by the Beirut explosion. Our analysis reveals that the induced wave structures arrived in the ionosphere 10 ± 2 min after the explosion, which is a strong indication of acoustic gravity wave activity. These wave structures are characterized with ΔTEC of 0.06 TECU moving at ∼750 m/s in south‐east direction away from the explosion epicenter. The continuous wavelet analysis we applied shows a dominant wave periodicity of 1.5–2.5 min (6.78–11 mHz ) in the ionosphere. Furthermore, we use measurements from ERA‐interim analysis to establish the ambient neutral atmospheric conditions before the Beirut explosion event. Finally, the observed ionospheric wave perturbations appear to be in good agreement with the expected arrival of acoustic gravity waves generated following the explosion.

The Thalassa mission concept was developed in response to the 2019 NASA Planetary Mission Concept Studies call. Using a multi-platform mission architecture, Thalassa seeks to address a single science goal: to determine the extent to which water has played a role in the geological evolution of Venus.

AbstractPhysics‐based Data Assimilation (DA) has been shown to be a powerful technique for specifying and predicting space weather. However, it is also known that different data assimilation models simulating the same geophysical event can display different space weather features even if the same data are assimilated. In this study, we used our Multimodel Ensemble Prediction System (MEPS) of DA models to elucidate the similarities and differences in the individual DA model reconstructions of the mid‐low latitude ionosphere when the same data are assimilated. Ensemble model averages were also obtained. For this ensemble modeling study, we selected the quiet/storm period of 16 and 17 March 2013 (equinox, solar medium). Five data assimilation models and one physics‐based model were used to produce an ensemble mean output for Total Electron Content (TEC), ionospheric peak density (NmF2), and ionospheric peak height (hmF2) for latitudes less than 60° and all longitudes. The data assimilated included ground‐based Global Positioning Satellite TEC and topside plasma densities near 800 km altitude derived from the COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) satellites. Both a simple average and a weighted average of the models were used in the ensemble averaging in order to determine if there was an improvement of the ensemble averages over the individual models.