Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.05.002
Giovanni La Mura , Giacomo Mulas , Maria Antonia Iatì , Cesare Cecchi-Pestellini , Shadi Rezaei , Rosalba Saija
In spite of accounting for only a small fraction of the mass of the Interstellar Medium (ISM), dust plays a primary role in many physical and chemical processes in the Universe. It is the main driver of extinction of radiation in the UV/optical wavelength range and a primary source of thermal IR emission. Dust grains contain most of the refractory elements of the ISM and they host chemical processes that involve complex molecular compounds. However, observational evidence suggests that grain structure is highly non-trivial and that dust particles are characterized by granularity, asymmetry and stratification, which significantly affect their interaction with radiation fields. Accurate modeling of such interaction is fundamental to properly explain observational results, but it is a computationally demanding task. Here we present the possibility to investigate the effects of radiation/particle interactions in non-spherically symmetric conditions using a novel implementation of the Transition Matrix formalism, designed to run on scalable parallel hardware facilities.
{"title":"Interstellar dust as a dynamic environment","authors":"Giovanni La Mura , Giacomo Mulas , Maria Antonia Iatì , Cesare Cecchi-Pestellini , Shadi Rezaei , Rosalba Saija","doi":"10.1016/j.asr.2025.05.002","DOIUrl":"10.1016/j.asr.2025.05.002","url":null,"abstract":"<div><div>In spite of accounting for only a small fraction of the mass of the Interstellar Medium (ISM), dust plays a primary role in many physical and chemical processes in the Universe. It is the main driver of extinction of radiation in the UV/optical wavelength range and a primary source of thermal IR emission. Dust grains contain most of the refractory elements of the ISM and they host chemical processes that involve complex molecular compounds. However, observational evidence suggests that grain structure is highly non-trivial and that dust particles are characterized by granularity, asymmetry and stratification, which significantly affect their interaction with radiation fields. Accurate modeling of such interaction is fundamental to properly explain observational results, but it is a computationally demanding task. Here we present the possibility to investigate the effects of radiation/particle interactions in non-spherically symmetric conditions using a novel implementation of the Transition Matrix formalism, designed to run on scalable parallel hardware facilities.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 4072-4081"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.072
Akshay S. Patil , Rani P. Pawar , Aditi D. Yadav , Dada P. Nade , T. Dharmaraj , Sanjay V. Pore , Sambhaji M. Pawar , Sunil D. Pawar
This research investigates the effects of thunderstorms on the ionosphere at the Indian Institute of Science (IISc), Bangalore, utilizing both ground-based and satellite observations. This study has identified significant ionospheric perturbations associated with thunderstorms by concentrating on lightning events under quiet solar and geomagnetic conditions (Kp < 5). During two pivotal events, enhanced Total Electron Content (TEC) variations were recorded at the GPS station at IISc Bangalore. In Event 1, the Vertical TEC (VTEC) fluctuated from +0.32 to −0.41 TEC units, with a temporal shift of 120 min. In Event 2, the VTEC exhibited variations ranging from +1.21 to −1.12 TEC units, with a shift of 150 min. The SABER temperature profiles revealed dominant wave characteristics with 12 km and 21 km vertical wavelengths at ∼80 km altitude for Events 1 and 2, respectively. Corresponding TEC wave-like oscillations exhibited vertical wavelengths of 42 km and 32 km at ∼300 km altitude, consistent with gravity wave dispersion dynamics. A strong link was established between lightning activity and atmospheric gravity waves (AGWs) observed by the SABER instrument, underscoring the interaction between the ionosphere and the lower atmosphere. Both events demonstrated a wave-like structure in the VTEC data, indicative of AGWs. The analysis of eight thunderstorm events revealed consistently observed ionospheric variations, with temporal delays ranging from 38 to 150 min.
{"title":"Investigating the signature of thunderstorm-generated gravity waves on low-latitude ionospheric dynamics","authors":"Akshay S. Patil , Rani P. Pawar , Aditi D. Yadav , Dada P. Nade , T. Dharmaraj , Sanjay V. Pore , Sambhaji M. Pawar , Sunil D. Pawar","doi":"10.1016/j.asr.2025.11.072","DOIUrl":"10.1016/j.asr.2025.11.072","url":null,"abstract":"<div><div>This research investigates the effects of thunderstorms on the ionosphere at the Indian Institute of Science (IISc), Bangalore, utilizing both ground-based and satellite observations. This study has identified significant ionospheric perturbations associated with thunderstorms by concentrating on lightning events under quiet solar and geomagnetic conditions (Kp < 5). During two pivotal events, enhanced Total Electron Content (TEC) variations were recorded at the GPS station at IISc Bangalore. In Event 1, the Vertical TEC (VTEC) fluctuated from +0.32 to −0.41 TEC units, with a temporal shift of 120 min. In Event 2, the VTEC exhibited variations ranging from +1.21 to −1.12 TEC units, with a shift of 150 min. The SABER temperature profiles revealed dominant wave characteristics with 12 km and 21 km vertical wavelengths at ∼80 km altitude for Events 1 and 2, respectively. Corresponding TEC wave-like oscillations exhibited vertical wavelengths of 42 km and 32 km at ∼300 km altitude, consistent with gravity wave dispersion dynamics. A strong link was established between lightning activity and atmospheric gravity waves (AGWs) observed by the SABER instrument, underscoring the interaction between the ionosphere and the lower atmosphere. Both events demonstrated a wave-like structure in the VTEC data, indicative of AGWs. The analysis of eight thunderstorm events revealed consistently observed ionospheric variations, with temporal delays ranging from 38 to 150 min.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 3508-3526"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.043
Xuan Peng , Fengli Dai
Focusing on inertia uncertainty and unwinding phenomenon in the quaternion-based attitude tracking control problem, this paper develops an anti-unwinding adaptive control algorithm based on the immersion and invariance (I&I) theory and a continuous hyperbolic sine function. To overcome the integrability obstacle inherent in I&I adaptive attitude control, an enhanced dynamic scaling technique is proposed. By ingeniously constructing the candidate Lyapunov function and scaling factor dynamics, constraints on control parameter values, as well as the requirements for the scaling factor and prior inertia information, are eliminated in the controller implementation, thereby reducing structural complexity and enhancing application flexibility. A continuous hyperbolic sine function is employed to construct a novel sliding mode surface, enabling the closed-loop adaptive system to have two stable equilibrium points, thus avoiding the unwinding without inducing switching chattering or initial attitude constraint. Finally, comparative simulations and analyses are conducted to demonstrate the features and efficacy of the proposed control strategy.
{"title":"Anti-unwinding immersion and invariance adaptive control for spacecraft attitude tracking","authors":"Xuan Peng , Fengli Dai","doi":"10.1016/j.asr.2025.11.043","DOIUrl":"10.1016/j.asr.2025.11.043","url":null,"abstract":"<div><div>Focusing on inertia uncertainty and unwinding phenomenon in the quaternion-based attitude tracking control problem, this paper develops an anti-unwinding adaptive control algorithm based on the immersion and invariance (I&I) theory and a continuous hyperbolic sine function. To overcome the integrability obstacle inherent in I&I adaptive attitude control, an enhanced dynamic scaling technique is proposed. By ingeniously constructing the candidate Lyapunov function and scaling factor dynamics, constraints on control parameter values, as well as the requirements for the scaling factor and prior inertia information, are eliminated in the controller implementation, thereby reducing structural complexity and enhancing application flexibility. A continuous hyperbolic sine function is employed to construct a novel sliding mode surface, enabling the closed-loop adaptive system to have two stable equilibrium points, thus avoiding the unwinding without inducing switching chattering or initial attitude constraint. Finally, comparative simulations and analyses are conducted to demonstrate the features and efficacy of the proposed control strategy.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 3872-3888"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.032
Shakir Ullah , Abdullah Alshehab , Muhammad Shohaib , Huda Alfannakh , Najeh Rekik
Space and laboratory plasmas frequently exhibit nonlinear behaviors, which are defined by ion-acoustic solitary waves and shock wave phenomena. These structures play a vital role in particle acceleration, energy transport, and interactions between spacecraft and plasma. Furthermore, space exploration missions commonly face plasma nonlinearities as their probes and spacecraft navigate through areas such as the solar wind, ionospheres, and planetary magnetospheres. The recent discovery of ion-acoustic solitary waves (IASWs) and ion-acoustic shock waves (IAShWs) by missions such as Voyager, Parker Solar Probe, and the Magnetospheric Multiscale Mission (MMS) highlight their significance in particle acceleration, spacecraft charging, and wave-particle interactions. These discoveries provide the impetus for our investigation into the formation and evolution of IASWs and IAShWs in a plasma of inertial ions and superthermal electrons. Spherical and cylindrical non-planar geometries are used to study the viscous, cold, and unmagnetized plasma that is under investigation. The nonplanar Korteweg-de Vries-Burgers (NKdVB) equation with dissipation effects are derived using the reductive perturbation approach. Analytical solutions of NKdVB equation are obtained by employing the weight residual and Hirota bilinear methods. Based on our investigations, the solitary and shock profiles are strongly affected by geometrical curvature, viscosity (), and the superthermality indices ( ). Specifically, the shocks are transformed into parabolic nonlinear systems by geometric effects, and these systems evolve with regard to the stretched time coordinate (). We acquire a better theoretical grasp of nonlinear ion-acoustic profiles and a foundation for understanding in situ spacecraft measurements from missions like MMS, Parker Solar Probe, and Voyager. Our results provide physical insights relevant to the nonlinear profiles identified in the solar wind, laser-generated plasma, and ionospheric plasma layer environments. This offers a theoretical foundation for interpreting in situ spacecraft data and assists in guiding laboratory plasma diagnostics.
{"title":"Nonlinear shock and solitary wave structures in nonplanar non-Maxwellian plasmas","authors":"Shakir Ullah , Abdullah Alshehab , Muhammad Shohaib , Huda Alfannakh , Najeh Rekik","doi":"10.1016/j.asr.2025.11.032","DOIUrl":"10.1016/j.asr.2025.11.032","url":null,"abstract":"<div><div>Space and laboratory plasmas frequently exhibit nonlinear behaviors, which are defined by ion-acoustic solitary waves and shock wave phenomena. These structures play a vital role in particle acceleration, energy transport, and interactions between spacecraft and plasma. Furthermore, space exploration missions commonly face plasma nonlinearities as their probes and spacecraft navigate through areas such as the solar wind, ionospheres, and planetary magnetospheres. The recent discovery of ion-acoustic solitary waves (IASWs) and ion-acoustic shock waves (IAShWs) by missions such as Voyager, Parker Solar Probe, and the Magnetospheric Multiscale Mission (MMS) highlight their significance in particle acceleration, spacecraft charging, and wave-particle interactions. These discoveries provide the impetus for our investigation into the formation and evolution of IASWs and IAShWs in a plasma of inertial ions and superthermal electrons. Spherical and cylindrical non-planar geometries are used to study the viscous, cold, and unmagnetized plasma that is under investigation. The nonplanar Korteweg-de Vries-Burgers (NKdVB) equation with dissipation effects are derived using the reductive perturbation approach. Analytical solutions of NKdVB equation are obtained by employing the weight residual and Hirota bilinear methods. Based on our investigations, the solitary and shock profiles are strongly affected by geometrical curvature, viscosity (<span><math><mrow><msub><mrow><mi>η</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span>), and the superthermality indices ( <span><math><mrow><mi>r</mi><mo>,</mo><mi>q</mi></mrow></math></span>). Specifically, the shocks are transformed into parabolic nonlinear systems by geometric effects, and these systems evolve with regard to the stretched time coordinate (<span><math><mrow><mi>τ</mi></mrow></math></span>). We acquire a better theoretical grasp of nonlinear ion-acoustic profiles and a foundation for understanding in situ spacecraft measurements from missions like MMS, Parker Solar Probe, and Voyager. Our results provide physical insights relevant to the nonlinear profiles identified in the solar wind, laser-generated plasma, and ionospheric plasma layer environments. This offers a theoretical foundation for interpreting in situ spacecraft data and assists in guiding laboratory plasma diagnostics.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 3983-3999"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.12.032
Prajwol B. Subedi , Hamdi A. Zurqani
Traditional field-based methods for estimating forest aboveground biomass (AGB) are constrained by limited scalability and spatial coverage, prompting the need for advanced, cost-effective solutions. Recent advancements in machine learning (ML) and deep learning (DL), coupled with remote sensing technologies, particularly NASA’s Global Ecosystem Dynamics Investigation (GEDI) spaceborne LiDAR, enable large-scale AGB estimation by capturing vertical forest structure and integrating multi-source optical data. However, the comparative performance and transferability of ML/DL models, with and without GEDI integration, across varying sensor resolutions remain insufficiently explored. This study bridges this gap through a two-phase analytical framework: (1) evaluating six algorithms, including Random Forest (RF), Gradient Tree Boosting (GTB), Classification and Regression Trees (CART), Deep Neural Networks (DNN), Convolutional Neural Networks (CNN), and Recurrent Neural Networks (RNN), using high-resolution NAIP imagery (0.3 m) and diverse feature sets (spectral indices, texture metrics, and topography); and (2) integrating top-performing models with GEDI-derived metrics to assess AGB estimation efficiency across NAIP, Sentinel-2, Landsat-8, and MODIS data. Model performance was rigorously validated using R2, RMSE, and NRMSE metrics, supplemented by SHAP analysis for interpretability. Results identified RF as the most accurate algorithm (R2 = 0.77, RMSE = 34.85 tonne per hectare (t ha−1), NRMSE = 5 %), surpassing DL models (e.g., DNN: R2 = 0.65). Multi-feature integration (e.g., vegetation indices, texture) significantly improved predictions over single-feature approaches. GEDI integration revealed resolution-dependent efficacy, with NAIP achieving superior accuracy (R2 = 0.72, RMSE = 24.13 t ha−1), while coarser-resolution sensors (Sentinel-2: R2 = 0.52; Landsat-8: R2 = 0.47; MODIS: R2 = 0.16) exhibited progressive declines. SHAP analysis underscored elevation, vegetation indices, and texture metrics as critical predictors. This research establishes a scalable framework for AGB estimation that employs RF-driven workflows and high-resolution data fusion to improve global forest monitoring and carbon stock assessments.
{"title":"Multi-sensor forest aboveground biomass estimation using GEDI, machine learning, and deep learning techniques","authors":"Prajwol B. Subedi , Hamdi A. Zurqani","doi":"10.1016/j.asr.2025.12.032","DOIUrl":"10.1016/j.asr.2025.12.032","url":null,"abstract":"<div><div>Traditional field-based methods for estimating forest aboveground biomass (AGB) are constrained by limited scalability and spatial coverage, prompting the need for advanced, cost-effective solutions. Recent advancements in machine learning (ML) and deep learning (DL), coupled with remote sensing technologies, particularly NASA’s Global Ecosystem Dynamics Investigation (GEDI) spaceborne LiDAR, enable large-scale AGB estimation by capturing vertical forest structure and integrating multi-source optical data. However, the comparative performance and transferability of ML/DL models, with and without GEDI integration, across varying sensor resolutions remain insufficiently explored. This study bridges this gap through a two-phase analytical framework: (1) evaluating six algorithms, including Random Forest (RF), Gradient Tree Boosting (GTB), Classification and Regression Trees (CART), Deep Neural Networks (DNN), Convolutional Neural Networks (CNN), and Recurrent Neural Networks (RNN), using high-resolution NAIP imagery (0.3 m) and diverse feature sets (spectral indices, texture metrics, and topography); and (2) integrating top-performing models with GEDI-derived metrics to assess AGB estimation efficiency across NAIP, Sentinel-2, Landsat-8, and MODIS data. Model performance was rigorously validated using R<sup>2</sup>, RMSE, and NRMSE metrics, supplemented by SHAP analysis for interpretability. Results identified RF as the most accurate algorithm (R<sup>2</sup> = 0.77, RMSE = 34.85 tonne per hectare (t ha<sup>−1</sup>), NRMSE = 5 %), surpassing DL models (e.g., DNN: R<sup>2</sup> = 0.65). Multi-feature integration (e.g., vegetation indices, texture) significantly improved predictions over single-feature approaches. GEDI integration revealed resolution-dependent efficacy, with NAIP achieving superior accuracy (R<sup>2</sup> = 0.72, RMSE = 24.13 t ha<sup>−1</sup>), while coarser-resolution sensors (Sentinel-2: R<sup>2</sup> = 0.52; Landsat-8: R<sup>2</sup> = 0.47; MODIS: R<sup>2</sup> = 0.16) exhibited progressive declines. SHAP analysis underscored elevation, vegetation indices, and texture metrics as critical predictors. This research establishes a scalable framework for AGB estimation that employs RF-driven workflows and high-resolution data fusion to improve global forest monitoring and carbon stock assessments.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 2784-2806"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.078
Boris Yu. Yushkov
A method of fast calculation of geomagnetic cutoff rigidity is presented. This method employs basic tables of cutoff rigidity calculated in the IGRF model in combination with a system of equations that recalculates basic rigidities for arbitrary coordinates, geomagnetic conditions and local time. The system of equations was obtained via generalization of results of direct computations of particle trajectories in the magnetic field defined as a superposition of the IGRF and Tsyganenko89 models. The basic table for the 2025 Epoch is presented and can be used until the year of 2030. Accuracy of cutoff rigidity determination is discussed.
{"title":"Fast calculation of geomagnetic cutoff rigidity","authors":"Boris Yu. Yushkov","doi":"10.1016/j.asr.2025.11.078","DOIUrl":"10.1016/j.asr.2025.11.078","url":null,"abstract":"<div><div>A method of fast calculation of geomagnetic cutoff rigidity is presented. This method employs basic tables of cutoff rigidity calculated in the IGRF model in combination with a system of equations that recalculates basic rigidities for arbitrary coordinates, geomagnetic conditions and local time. The system of equations was obtained via generalization of results of direct computations of particle trajectories in the magnetic field defined as a superposition of the IGRF and Tsyganenko89 models. The basic table for the 2025 Epoch is presented and can be used until the year of 2030. Accuracy of cutoff rigidity determination is discussed.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 3549-3555"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.096
Ankit Gupta , Qadeer Ahmed , Anshul Singh , Aastha Rawat , Arti Bhardwaj , Puja Goel , A.K. Upadhayaya
We investigated the ionospheric response to four intense geomagnetic storms that occurred in 2023 and 2024, near the peak of Solar Cycle 25, which were powerful enough to trigger rare auroral displays at unusually low latitudes, including the high-altitude astronomy observatory located in Hanle, India. Among the events analyzed, the geomagnetic storm of 11 May 2024 (Sym-H = −520 nT) resulted in a radio blackout and a complete disappearance of ionograms for nearly five hours during its main phase due to enhanced D-region ionization (electron density up to ), and F layer uplift beyond 550 km — an extreme ionospheric disturbance not witnessed during the 23rd and 24th solar cycles at this station. The storms on 11 May 2024, 11 October 2024, and 24 April 2023 showed strong negative storm phases, followed by positive dayside enhancements, while the 05 November 2023 storm displayed a main-phase enhancement of electron density. These contrasting behaviours were primarily governed by the interplay of prompt penetration electric fields (PPEFs), local time dependent ionization and thermospheric density, with recombination rates varying by 54, 15.7, 2.4, and 0.68, respectively. While elevated interplanetary electric field (>2.5 mV/m) and solar wind dynamic pressure (SWDP > 15 nPa) drive storm intensity, sustained high independently triggers significant ionospheric responses. The IRI model reproduced variations well for most storm events, but showed significant deviations (up to ±5 MHz) during the intense 11 May 2024 storm, with a positive mean bias error and a reduced correlation coefficient of 0.65, underscoring its limitations under extreme geomagnetic conditions.
{"title":"Ionospheric response of intense geomagnetic storms near the peak phase of Solar Cycle 25 at low mid-latitude Indian station, New Delhi","authors":"Ankit Gupta , Qadeer Ahmed , Anshul Singh , Aastha Rawat , Arti Bhardwaj , Puja Goel , A.K. Upadhayaya","doi":"10.1016/j.asr.2025.11.096","DOIUrl":"10.1016/j.asr.2025.11.096","url":null,"abstract":"<div><div>We investigated the ionospheric response to four intense geomagnetic storms that occurred in 2023 and 2024, near the peak of Solar Cycle 25, which were powerful enough to trigger rare auroral displays at unusually low latitudes, including the high-altitude astronomy observatory located in Hanle, India. Among the events analyzed, the geomagnetic storm of 11 May 2024 (Sym-H = −520 nT) resulted in a radio blackout and a complete disappearance of ionograms for nearly five hours during its main phase due to enhanced D-region ionization (electron density up to <span><math><mrow><msup><mrow><mn>10</mn></mrow><mrow><mn>10</mn></mrow></msup><msup><mrow><mi>m</mi></mrow><mrow><mo>-</mo><mn>3</mn></mrow></msup></mrow></math></span>), and F layer uplift beyond 550 km — an extreme ionospheric disturbance not witnessed during the 23rd and 24th solar cycles at this station. The storms on 11 May 2024, 11 October 2024, and 24 April 2023 showed strong negative storm phases, followed by positive dayside enhancements, while the 05 November 2023 storm displayed a main-phase enhancement of electron density. These contrasting behaviours were primarily governed by the interplay of prompt penetration electric fields (PPEFs), local time dependent ionization and thermospheric density, with recombination rates varying by 54, 15.7, 2.4, and 0.68, respectively. While elevated interplanetary electric field <span><math><mrow><msub><mrow><mi>E</mi></mrow><mrow><mi>y</mi></mrow></msub></mrow></math></span> (>2.5 mV/m) and solar wind dynamic pressure (SWDP > 15 nPa) drive storm intensity, sustained high <span><math><mrow><msub><mrow><mi>E</mi></mrow><mrow><mi>y</mi></mrow></msub></mrow></math></span> independently triggers significant ionospheric responses. The IRI model reproduced <span><math><mrow><msub><mrow><mi>f</mi></mrow><mrow><mi>o</mi></mrow></msub><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> variations well for most storm events, but showed significant deviations (up to ±5 MHz) during the intense 11 May 2024 storm, with a positive mean bias error and a reduced correlation coefficient of 0.65, underscoring its limitations under extreme geomagnetic conditions.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 3594-3617"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.084
Dibyendu Ghosh, Somen Das
Flood susceptibility analysis and shelter suitability assessment are essential components of flood risk management. This study integrates machine learning (ML) models with multi-criteria decision-making to enhance preparedness in the Mahananda River Basin. A total of 16 flood-conditioning parameters, identified through principal component analysis, multicollinearity testing, and correlation attribute evaluation, were used to construct models. Fifteen ML and deep learning (DL) algorithms were applied to predict flood-prone zones, and their performances were assessed through multiple accuracy metrics. Among them, the stacking ensemble model achieved the highest predictive accuracy, providing a robust basis for susceptibility mapping. In parallel, the Analytical Hierarchy Process (AHP) was used to determine shelter suitability by incorporating criteria such as flood susceptibility, elevation, road accessibility, proximity to hospitals and fire stations, settlement concentration, and land use/land cover. The integrated results not only delineated high-risk flood zones but also identified suitable locations for flood shelters, particularly across settlement areas of Raiganj, Kaliaganj, Malda, Gazole, Dalkhola, and Rashidpur. The findings deliver both a reliable flood susceptibility framework and a prioritized shelter suitability plan, contributing to disaster mitigation, community safety, and long-term resilience in the Mahananda River Basin.
{"title":"Modeling flood susceptibility and identifying optimal flood shelters for effective flood management in the Mahananda River Basin","authors":"Dibyendu Ghosh, Somen Das","doi":"10.1016/j.asr.2025.11.084","DOIUrl":"10.1016/j.asr.2025.11.084","url":null,"abstract":"<div><div>Flood susceptibility analysis and shelter suitability assessment are essential components of flood risk management. This study integrates machine learning (ML) models with multi-criteria decision-making to enhance preparedness in the Mahananda River Basin. A total of 16 flood-conditioning parameters, identified through principal component analysis, multicollinearity testing, and correlation attribute evaluation, were used to construct models. Fifteen ML and deep learning (DL) algorithms were applied to predict flood-prone zones, and their performances were assessed through multiple accuracy metrics. Among them, the stacking ensemble model achieved the highest predictive accuracy, providing a robust basis for susceptibility mapping. In parallel, the Analytical Hierarchy Process (AHP) was used to determine shelter suitability by incorporating criteria such as flood susceptibility, elevation, road accessibility, proximity to hospitals and fire stations, settlement concentration, and land use/land cover. The integrated results not only delineated high-risk flood zones but also identified suitable locations for flood shelters, particularly across settlement areas of Raiganj, Kaliaganj, Malda, Gazole, Dalkhola, and Rashidpur. The findings deliver both a reliable flood susceptibility framework and a prioritized shelter suitability plan, contributing to disaster mitigation, community safety, and long-term resilience in the Mahananda River Basin.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 3258-3280"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.11.050
Ayşe Yadikar Habalı , Volkan Bakış
Young stellar objects (YSOs) are commonly classified based on their infrared spectral energy distributions (SEDs), but the reliability of large-scale photometric classification remains affected by extinction, sample contamination, and distance uncertainties. In this study, we compile a physically validated catalog of 17854 YSOs from 105 literature sources, spanning all major evolutionary stages. For 16472 sources with sufficient multi-band photometry, we determine the infrared spectral index via a simple log–log regression of the 2–24 μm SED. While this method does not involve physical model fitting, it provides an efficient statistical tool to distinguish between Class 0/I, Flat Spectrum, Class II, and Class III sources. We assess and quantify the impact of line-of-sight extinction using the Bayestar19 3D dust map and derive values for the full sample. Although most sources have mag, we identify a subset with significant extinction that may bias -based classifications. A weak but statistically significant correlation () is found between and , suggesting that extinction may systematically alter the observed slope of the infrared SED. Using mid-infrared WISE and near-infrared 2MASS photometry, calibrated with Gaia-based distances, we construct absolute color–magnitude and color–color diagrams that show clear evolutionary separability. We also derive an empirical relation to estimate from infrared colors alone, achieving a strong correlation (). This relation enables classification of 956 additional sources lacking full SED coverage. Our framework provides a reliable method for photometric classification of YSOs in large infrared surveys, with explicit consideration of extinction effects.
{"title":"A color–magnitude approach to YSO classification using SED slope and Gaia-distance-calibrated WISE/2MASS photometry","authors":"Ayşe Yadikar Habalı , Volkan Bakış","doi":"10.1016/j.asr.2025.11.050","DOIUrl":"10.1016/j.asr.2025.11.050","url":null,"abstract":"<div><div>Young stellar objects (YSOs) are commonly classified based on their infrared spectral energy distributions (SEDs), but the reliability of large-scale photometric classification remains affected by extinction, sample contamination, and distance uncertainties. In this study, we compile a physically validated catalog of 17854 YSOs from 105 literature sources, spanning all major evolutionary stages. For 16472 sources with sufficient multi-band photometry, we determine the infrared spectral index <span><math><mrow><mi>α</mi></mrow></math></span> via a simple log–log regression of the 2–24 μm SED. While this method does not involve physical model fitting, it provides an efficient statistical tool to distinguish between Class 0/I, Flat Spectrum, Class II, and Class III sources. We assess and quantify the impact of line-of-sight extinction using the Bayestar19 3D dust map and derive <span><math><mrow><msub><mrow><mi>A</mi></mrow><mrow><mi>V</mi></mrow></msub></mrow></math></span> values for the full sample. Although most sources have <span><math><mrow><msub><mrow><mi>A</mi></mrow><mrow><mi>V</mi></mrow></msub><mo><</mo><mn>2</mn></mrow></math></span> mag, we identify a subset with significant extinction that may bias <span><math><mrow><mi>α</mi></mrow></math></span>-based classifications. A weak but statistically significant correlation (<span><math><mrow><mi>r</mi><mo>=</mo><mn>0.32</mn><mo>,</mo><mi>p</mi><mo>≪</mo><mn>0.001</mn></mrow></math></span>) is found between <span><math><mrow><mi>α</mi></mrow></math></span> and <span><math><mrow><msub><mrow><mi>A</mi></mrow><mrow><mi>V</mi></mrow></msub></mrow></math></span>, suggesting that extinction may systematically alter the observed slope of the infrared SED. Using mid-infrared WISE and near-infrared 2MASS photometry, calibrated with Gaia-based distances, we construct absolute color–magnitude and color–color diagrams that show clear evolutionary separability. We also derive an empirical relation to estimate <span><math><mrow><mi>α</mi></mrow></math></span> from infrared colors alone, achieving a strong correlation (<span><math><mrow><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≈</mo><mn>0.98</mn></mrow></math></span>). This relation enables classification of 956 additional sources lacking full SED coverage. Our framework provides a reliable method for photometric classification of YSOs in large infrared surveys, with explicit consideration of extinction effects.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 4018-4039"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.asr.2025.04.058
S. Komossa , D. Grupe , P. Marziani , L.Č. Popović , S. Marčeta-Mandić , E. Bon , D. Ilić , A.B. Kovačević , A. Kraus , Z. Haiman , V. Petrecca , D. De Cicco , M.S. Dimitrijević , V.A. Srećković , J. Kovačević Dojčinović , M. Pannikkote , N. Bon , K.K. Gupta , F. Iacob
The extremes of Active Galactic Nuclei (AGN) variability offer valuable new insights into the drivers and physics of AGN. We discuss some of the most extreme cases of AGN variability; the highest amplitudes, deep minima states, extreme spectral states, Seyfert-type changes, and semi-periodic signals, including new X-ray observations. The properties of changing-look (CL) AGN are briefly reviewed and a classification scheme is proposed which encompasses the variety of CL phenomena; distinguishing slow and fast events, repeat events, and frozen-look AGN which do not show any emission-line response. Long-term light curves that are densely covered over multiple years, along with follow-up spectroscopy, are utilized to gain insight into the underlying variability mechanisms including accretion disk and broad-line region physics. Remarkable differences are seen, for instance, in the optical spectral response to extreme outbursts, implying distinct intrinsic variability mechanisms. Furthermore, we discuss methods for distinguishing between CL AGN and CL look-alike events (tidal disruption events or supernovae in dense media). Finally, semi-periodic light curve variability is addressed and the latest multiwavelength (MWL) light curve of the binary supermassive black hole (SMBH) candidate OJ 287 from the MOMO project is presented. Recent results from that project have clearly established the need for new binary SMBH modelling matching the tight new constraints from observations, including the measurement of a low (primary) SMBH mass of M⊙ which also implies that OJ 287 is no longer in the regime of near-future pulsar timing arrays.
{"title":"The extremes of AGN variability: Outbursts, deep fades, changing looks, exceptional spectral states, and semi-periodicities","authors":"S. Komossa , D. Grupe , P. Marziani , L.Č. Popović , S. Marčeta-Mandić , E. Bon , D. Ilić , A.B. Kovačević , A. Kraus , Z. Haiman , V. Petrecca , D. De Cicco , M.S. Dimitrijević , V.A. Srećković , J. Kovačević Dojčinović , M. Pannikkote , N. Bon , K.K. Gupta , F. Iacob","doi":"10.1016/j.asr.2025.04.058","DOIUrl":"10.1016/j.asr.2025.04.058","url":null,"abstract":"<div><div>The extremes of Active Galactic Nuclei (AGN) variability offer valuable new insights into the drivers and physics of AGN. We discuss some of the most extreme cases of AGN variability; the highest amplitudes, deep minima states, extreme spectral states, Seyfert-type changes, and semi-periodic signals, including new X-ray observations. The properties of changing-look (CL) AGN are briefly reviewed and a classification scheme is proposed which encompasses the variety of CL phenomena; distinguishing slow and fast events, repeat events, and frozen-look AGN which do not show any emission-line response. Long-term light curves that are densely covered over multiple years, along with follow-up spectroscopy, are utilized to gain insight into the underlying variability mechanisms including accretion disk and broad-line region physics. Remarkable differences are seen, for instance, in the optical spectral response to extreme outbursts, implying distinct intrinsic variability mechanisms. Furthermore, we discuss methods for distinguishing between CL AGN and CL look-alike events (tidal disruption events or supernovae in dense media). Finally, semi-periodic light curve variability is addressed and the latest multiwavelength (MWL) light curve of the binary supermassive black hole (SMBH) candidate OJ 287 from the MOMO project is presented. Recent results from that project have clearly established the need for new binary SMBH modelling matching the tight new constraints from observations, including the measurement of a low (primary) SMBH mass of <span><math><mrow><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup></mrow></math></span> M<sub>⊙</sub> which also implies that OJ 287 is no longer in the regime of near-future pulsar timing arrays.</div></div>","PeriodicalId":50850,"journal":{"name":"Advances in Space Research","volume":"77 3","pages":"Pages 4041-4058"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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