Earth, Planets and Space最新文献

{"title":"Forecasting secular variation using physics-informed neural networks for IGRF-14.","authors":"N Shakespeare-Rees, P W Livermore, C J Davies, H F Rogers, C D Beggan, W J Brown, C C Finlay","doi":"10.1186/s40623-026-02427-6","DOIUrl":"10.1186/s40623-026-02427-6","url":null,"abstract":"<p><p>In response to the call for candidate models for the 14th generation of the International Geomagnetic Reference Field (IGRF) by the Geomagnetic Field Modeling Working Group (V-MOD) of the International Association of Geomagnetism and Aeronomy (IAGA), we present the University of Leeds candidate model for the forecast of the average Secular Variation (SV) for 2025-2030. Our approach consists of inverting the geomagnetic field model CHAOS-7.18 using Physics-Informed Neural Networks to produce two global mesh-free models from (i) a mosaic of independent regional flows and (ii) a single global flow representation. The magnetic field is then advected under the assumption of steady core flow over a 5-year period, and the average SV over 5 years is taken to construct the forecast. We validate our approach using hindcasts for the IGRF-13 time period (2020-2025) and benchmark our methodology against the inferred SV from CHAOS-7.18. Our field models constructed from regional flows show reduced RMS misfit relative to the field from the CHAOS-7.18 model at each yearly timestep, compared to the other candidate models from IGRF-13 in the hindcast, both at the Core Mantle Boundary and at the Earth's Surface. We then present our IGRF-14 candidate forecast for the period 2025-2030, derived from the regional method, and discuss possible improvements to this method for future IGRF submissions.</p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"98"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13149576/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147867205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"IGRF-14 secular variation prediction from core surface flow acceleration.","authors":"Frederik Dahl Madsen, Ciarán D Beggan, William J Brown, Richard Holme, Jonas Bregnhøj Lauridsen, Kathryn A Whaler","doi":"10.1186/s40623-025-02347-x","DOIUrl":"10.1186/s40623-025-02347-x","url":null,"abstract":"<p><strong>Abstract: </strong>The International Geomagnetic Reference Field (IGRF) has been regularly updated since its inception in 1965. Every recent iteration contains an estimate of the geomagnetic secular variation (SV), for the intermediate years between iterations. We submit a candidate model for the geomagnetic secular variation (SV) for the period 2025-2030 for the 14^th generation of the IGRF. Given the recent evidence in the geomagnetic SV record for core surface waves, we forecast SV based on the periodic behaviour of core surface flow acceleration. We obtain an advective core surface flow model, in terms of poloidal and toroidal flow coefficients, from spatial gradients of SV geomagnetic virtual observatory data from the low-Earth orbiting CHAMP and Swarm missions from January 2001 to January 2010, and April 2014 to January 2024, respectively. From these, we calculate the flow acceleration coefficients from the first time-derivative. This assumes the flow is spatio-temporally simple, without imposing any physical constraints on its geometry. We fit each acceleration coefficient with a sinusoidal function, which is used to extrapolate 6 years into the future. These sinusoidally varying acceleration time series are integrated over time to obtain the core flow coefficients, which are then used to predict the average advected SV over the 5-year IGRF period. We recreate previous IGRF predictions using our CHAMP-based flows to validate our methodology, which we find to outperform previous IGRF iterations, and use the Swarm-based flows to forecast the SV for IGRF-14. Our Swarm-based model predicts sudden changes in SV-also known as geomagnetic jerks-in 2024 in the Equatorial Pacific, and in 2028 in the region around central Africa. Although the IGRF SV is a snapshot over a 5-year period, allowing for periodic behaviour offers potential improvements over other methods of prediction.</p><p><strong>Graphical abstract: </strong></p><p><strong>Supplementary information: </strong>The online version contains supplementary material available at 10.1186/s40623-025-02347-x.</p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"29"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12891054/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146178568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preliminary tide gauge evidence for equilibrium and non-equilibrium pole tide variability after the 2015 Chandler Wobble amplitude reduction.","authors":"Taehwan Jeon, Ki-Weon Seo, Kookhyoun Youm, Jooyoung Eom, Jianli Chen, Clark R Wilson","doi":"10.1186/s40623-026-02461-4","DOIUrl":"10.1186/s40623-026-02461-4","url":null,"abstract":"<p><p>The pole tide has been defined as the oceanic response to polar motion, with a component due to the Chandler Wobble (CW), at a period near 14 months. The magnitude of the CW was greatly reduced after about 2015, and a corresponding global attenuation of the ocean pole tide amplitude is expected. We analyzed global tide gauge measurements using empirical orthogonal functions (EOF) methods to separate temporal and spatial patterns of regional pole tide signals. Our results show that tide gauge arrays in Japan and along the east coast of North America exhibit 14-month pole tide signals whose temporal variability is broadly consistent with the CW amplitude reduction after 2015. At stations in both regions, EOF-based mean pole tide amplitudes since 1980 fall in the range of approximately 0.5-1 cm, representing a more coherent signal than direct spectral estimates from individual stations. These amplitudes exceed the expected equilibrium response (less than 0.5 cm), suggesting that they reflect a mixture of equilibrium and moderate non-equilibrium contributions. Tide gauges in the North Sea and Baltic Sea show no detectable amplitude decrease after ~ 2015, consistent with previous studies documenting strong non-equilibrium pole tide variability in these regions. Together with the partial agreement with equilibrium expectations in Japan and along the North American east coast, these results suggest that regional pole tide signals likely reflect a combination of equilibrium response and additional forcing, potentially including long-period atmospheric variability.</p><p><strong>Graphical abstract: </strong></p><p><strong>Supplementary information: </strong>The online version contains supplementary material available at 10.1186/s40623-026-02461-4.</p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"139"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13350126/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148419674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How do core surface flow models vary when inverted from IGRF-14 candidate field models?","authors":"H F Rogers, M Mandea","doi":"10.1186/s40623-025-02307-5","DOIUrl":"10.1186/s40623-025-02307-5","url":null,"abstract":"<p><p>The International Geomagnetic Reference Field (IGRF) model is a series of models that describe the large scale magnetic field measured at the Earth's surface. It is used by a wide range of scientists and industries, including in navigation, space weather applications, and resource exploration. The 14th generation, IGRF-14, is the result of an international collaboration over 19 different lead research groups. This new generation provides a definitive model of the main magnetic field (MF) for the epoch 2020.0, a prediction of the MF for 2025.0, and a predicted average annual time variation of the magnetic field for 2025.0 <math><mo>-</mo></math> 2030.0. The first time derivative of the magnetic field, known as secular variation, (SV) is linked to the flow at the top of Earth's outer core. As such, the ensemble of IGRF-14 candidate models can be used to investigate predicted core flow variability between 2020.0 and 2030.0. We use the pygeodyn Python package using the AR-1 'dense' methodology, the 71% geodynamo prior, and keep all inversion parameters fixed to ensure that differences in inferred flow arise solely from variations from the IGRF candidate models. Our results demonstrate that while all candidates produce broadly similar flow spectra for all degrees, candidates that deviate most from the median IGRF model also show the largest differences in flow. In all cases, the flow speed difference remains below 25% of the maximum flow speed of the Huber-weighted mean model in space, with most discrepancies occurring at small spatial scales. The greatest flow uncertainty appears over the Pacific and in the polar regions, where constraints are weaker. Finally, we assess the impact of the maximum spherical harmonic degree truncation of the SV candidate models by comparing two SV candidates truncated at spherical harmonic degree 13 instead of 8. Increasing the truncation degree of SV alters the flow spectral energy at all degrees and increases the maximum flow speed by up to 31%, despite the flow maps remaining highly correlated. This study supports the idea of raising the spherical harmonic truncation degree to 13 for the SV prediction component of the IGRF.</p><p><strong>Graphical abstract: </strong></p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"39"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12948799/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147324879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SSTAR: a user-friendly framework for detecting and monitoring subtle thermal precursors to volcanic eruptions-application to Shishaldin, Alaska.","authors":"Társilo Girona, Laure Brenot","doi":"10.1186/s40623-026-02497-6","DOIUrl":"10.1186/s40623-026-02497-6","url":null,"abstract":"<p><p>In recent decades, the monitoring of volcanoes has been revolutionized by the launch of Earth-observing satellites and advances in thermal infrared remote sensing. These developments have revealed a wide range of thermal responses of volcanic surfaces to subsurface processes, even demonstrating that eruptions are often preceded by measurable thermal anomalies. This recognition highlights the need for robust tools to systematically detect and track such anomalies, making full use of existing satellite datasets and maximizing the value of current instruments in orbit. To address this challenge, we present the <i>Subtle Surface Thermal Anomalies Recognizer</i> (SSTAR), a versatile and user-friendly application designed to analyze diffuse thermal anomalies, i.e., subtle thermal unrest (~ 1 K) across large areas (several km²). SSTAR leverages data from NASA's Terra and Aqua satellites, which host the Moderate Resolution Imaging Spectroradiometers (MODIS), and builds upon a robust statistical framework. By processing pixel-level data, SSTAR tracks the temporal evolution of diffuse thermal anomalies at specific target sites and maps their spatiotemporal distribution across extended areas. Key features include filtering tools that distinguish between long-term (years) and short-term (weeks) anomalies, as well as uncertainty quantification using bootstrapping. The application is standalone, features an interactive interface for streamlined analysis, and is accessible to newcomers to satellite-based thermal remote sensing. At the same time, specialized users can customize the underlying scripts for other specific research needs. As a demonstration, we apply SSTAR to Shishaldin volcano (Alaska), revealing the emergence of significant thermal anomalies around the summit crater and flanks prior to eruptions. We envision SSTAR as a valuable resource for studying subtle thermal unrest at active volcanoes and hydrothermal systems, where the detection of faint and spatially coherent anomalies may help identify subsurface fluid pathways. Its flexible design enables integration with additional satellite datasets, positioning SSTAR as a forward-looking tool for advancing space-based volcanic thermal monitoring. Building on this capability, daily updated diffuse thermal anomalies are provided for target volcanoes through an open web platform hosted at Geosciences Barcelona-CSIC (https://sstar.geo3bcn.csic.es/), to support surveillance agencies and expert committees in alert-level assessments.</p><p><strong>Graphical abstract: </strong></p><p><strong>Supplementary information: </strong>The online version contains supplementary material available at 10.1186/s40623-026-02497-6.</p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"166"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13391715/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148577513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A database of geomagnetic observatory monthly means: from historic to the satellite era.","authors":"William Brown, Susan Macmillan, Eleanor Maume, Eliot Eaton","doi":"10.1186/s40623-025-02316-4","DOIUrl":"10.1186/s40623-025-02316-4","url":null,"abstract":"<p><p>This work brings together the contents of previously disparate databases of absolute ground geomagnetic observations, both historic and ongoing, to process the data consistently into a coherent and accessible format for researchers. This includes converting reported time resolutions and coordinate systems into a uniform format, and applying all documented observatory baseline changes to the data records, to create a single unified vector time series of monthly mean values for each geomagnetic observatory. The data are made available freely and anonymously to researchers via a web service, updated on a monthly basis with the latest definitive and non-definitive observations reported to the World Data Centre for Geomagnetism (Edinburgh) and INTERMAGNET or Tromsø Geophysical Observatory, respectively. The current database covers 327 observatories worldwide, with observations from 1883 up until present. A separate effort involved digitising tables of monthly means in the 1841-1925 yearbooks of the Royal Observatory, Greenwich, United Kingdom and converting to homogeneous units. The resulting data represent some of the earliest magnetic data at monthly time resolution and may be of use to future studies. However, they cannot be incorporated into the monthly means database as the field vector information is incomplete; we publicise them here instead.</p><p><strong>Graphical abstract: </strong></p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"7"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12804219/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145997476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Model calculations for neutron-induced reactions in meteorites and planetary surfaces.","authors":"Ingo Leya","doi":"10.1186/s40623-025-02358-8","DOIUrl":"10.1186/s40623-025-02358-8","url":null,"abstract":"<p><p>This study investigates the capabilities of the GEANT4 Monte Carlo toolkit to quantitatively predict neutron production, neutron transport, and nuclide production by neutron capture reactions in cosmochemical relevant objects. The model reproduces neutron densities measured in the lunar surface within the experimental uncertainties, which is a major improvement compared to earlier studies. Since, for many applications in meteorites and planetary surfaces, nuclide production by neutron capture is of importance, the production of <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>41</mn></mmultiscripts> </math> Ca and <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>60</mn></mmultiscripts> </math> Co is studied as an example. In addition, shifts in the stable isotope ratios <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>157</mn></mmultiscripts> </math> Gd/ <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>160</mn></mmultiscripts> </math> Gd, <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>158</mn></mmultiscripts> </math> Gd/ <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>160</mn></mmultiscripts> </math> Gd, <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>149</mn></mmultiscripts> </math> Sm/ <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>152</mn></mmultiscripts> </math> Sm, and <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>150</mn></mmultiscripts> </math> Sm/ <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>152</mn></mmultiscripts> </math> Sm (and combinations thereof) are modeled and compared to experimental data. The model describes experimental <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>41</mn></mmultiscripts> </math> Ca activity concentrations in different types of meteorites and the lunar surface within the uncertainties. In contrast, it fails to describe <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>60</mn></mmultiscripts> </math> Co activity concentrations. In addition, it is difficult to consistently model the isotope shifts <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>157</mn></mmultiscripts> </math> Gd/ <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>160</mn></mmultiscripts> </math> Gd and <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>150</mn></mmultiscripts> </math> Sm/ <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>152</mn></mmultiscripts> </math> Sm in Apollo 15 drill core samples. The observed trends depend on the temperature of the irradiated object and are more pronounced for colder temperatures. Since the observed discrepancies are likely related to the shape of the neutron spectra, self-shielding effects by, e.g., <math><mmultiscripts><mrow></mrow> <mrow></mrow> <mn>56</mn></mmultiscripts> </math> Fe, might be of importance and some of the consequences are discussed.</p><p><strong>Graphical abstract: </strong></p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"27"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12891260/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146178695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global data-driven predictions of seasonal non-tectonic signals in vertical GNSS displacement time series from non-tidal surface loading data.","authors":"Kaan Çökerim, Henryk Dobslaw, Kyriakos Balidakis, Laura Jensen, Carlos Peña, Jonathan Bedford","doi":"10.1186/s40623-026-02385-z","DOIUrl":"10.1186/s40623-026-02385-z","url":null,"abstract":"<p><p>Daily displacement time series from Global Navigation Satellite Systems (GNSS) are frequently used to study deformations of the Earth's surface due to a wide range of different geophysical processes. The recorded deformations result from tectonic activity or non-tectonic processes like volcanism, groundwater fluctuations and atmospheric loading. In addition, local disturbances of the antenna (e.g., snow cover, thermoelastic effects of the monumentation) and artifacts from GNSS processing (e.g., draconitic signals) are sometimes prominently included in coordinate time series. We use a Temporal Convolution Network (TCN) to predict non-tectonic vertical GNSS displacements on a global scale from physics-based non-tidal loading products. We train our model on a global dataset with more than 11,000 GNSS stations from the Nevada Geodetic Laboratory, active from January 2002 until June 2024, and evaluate the performance against independent estimations. Across the hold-out dataset, our TCN derives non-tidal loading GNSS signatures that when compared to the non-tectonic GNSS signal results in a global average reduction in RMSE of 4.7 % with respect to the numerical non-tidal loading models. This approach presents an initial step towards a data-driven complement to physics-based numerical loading models, improving the isolation of non-tectonic signals in GNSS time series and validation of numerical non-tidal loading models.</p><p><strong>Graphical abstract: </strong></p><p><strong>Supplementary information: </strong>The online version contains supplementary material available at 10.1186/s40623-026-02385-z.</p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"56"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13021762/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147572799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimation of auroral emission altitude in the region of the ISS magnetic footprint during a relativistic electron precipitation event observed by ISS-CALET.","authors":"Kyutaro Yanagisawa, Ryuho Kataoka, Kanako Seki, Daniel Whiter, Yoshizumi Miyoshi, Kazuo Shiokawa, Martin Connors, Shoji Torii, Satoshi Nakahira, Takeshi Sakanoi, Raju Aryal, Alessandro Bruno, Lauren W Blum","doi":"10.1186/s40623-026-02507-7","DOIUrl":"10.1186/s40623-026-02507-7","url":null,"abstract":"<p><p>We report a multi-MeV relativistic electron precipitation (REP) event as observed by the CALorimetric Electron Telescope and the Monitor of All-sky X-ray Image aboard the International Space Station, together with low-cost twin all-sky auroral imagers installed at Athabasca, Canada. We find that visible auroral emissions near the ISS magnetic footprint during REP events are not frequent-observed in only two of 10 conjugate REP events during our survey period from September 2024 to September 2025-and that one case, on 3 May 2025, featured diffuse aurora near the ISS magnetic footprint. Using two independent stereoscopic methods, we estimate the auroral emission height to be ~90 km, which is typically produced by tens-of-keV electron precipitation. Combined with the MeV electron precipitation detected by CALET, such broadband electron precipitation from tens-of-keV to MeV is consistent with the hypothesis of chorus-driven REP events. The emission altitude shows no systematic latitudinal variation, which is not consistent with field-line curvature scattering type energy-dispersed precipitation. The combined space- and ground-based observations contribute to a better understanding of the spatial context of wave-particle interaction associated with the REP events.</p><p><strong>Graphical abstract: </strong></p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"205"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13588871/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149008107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The spatiotemporal development of the midlatitude troughs and subauroral ion drift during a geomagnetic storm observed by multiple DMSP satellites.","authors":"Heechan Cha, Jerry Goldstein, Dhirendra Kataria, Yukitoshi Nishimura, Keiichi Ogasawara","doi":"10.1186/s40623-025-02349-9","DOIUrl":"10.1186/s40623-025-02349-9","url":null,"abstract":"<p><strong>Abstract: </strong>Subauroral ion drift (SAID) is a narrow and rapid westward ion flow observed in the subauroral ionosphere during geomagnetic storms and substorms. It is more localized and intense than subauroral polarization streams (SAPS), typically appearing equatorward of auroral boundaries and often associated with midlatitude troughs. This study analyzes ion drifts and plasma density variations using DMSP F16, F17, and F18 data from June 1, 2013, in the Southern Hemisphere. Using multi-satellite observations from three DMSP spacecraft, we systematically examine the spatiotemporal evolution of a SAID event and its associated midlatitude troughs, focusing on their relation to geomagnetic storm phases and substorm activity. We develop an ad hoc empirical model that reproduces SAID spatial distribution and temporal evolution by establishing a quantitative relationship between SAID velocity and the AE index. From the results, we present two key findings: first, we identified a previously unreported two-stage development pattern of SAID: equatorward expansion with minimal width change and moderate potential drop in the early main phase, followed by latitudinal stabilization, width variation, and stronger electric fields in the late main phase. Second, we newly identified that the midlatitude trough developed through three distinct stages: mild density gradient associated with the initial AE increase, sharp density drop at the plasmapause boundary after the first AE decrease, and persistent deep trough after first AE peak and throughout the second AE peak lasted for three hours. These findings and our empirical modeling approach provide new quantitative insights into the distinct temporal evolution patterns of SAID and midlatitude troughs, advancing further understanding of the connection between ionospheric disturbances and geomagnetic storms.</p><p><strong>Graphical abstract: </strong></p>","PeriodicalId":11409,"journal":{"name":"Earth, Planets and Space","volume":"78 1","pages":"14"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12847133/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146084898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}