Solar Physics最新文献

{"title":"Long-term Evolution of Chromospheric Plage Areas from Kodaikanal Observatory Ca ii K Images and Their Relation to Solar Activity Indices","authors":"Partha Chowdhury,&nbsp;Jagdev Singh,&nbsp;V. Muthu Priyal,&nbsp;Belur Ravindra","doi":"10.1007/s11207-026-02733-y","DOIUrl":"10.1007/s11207-026-02733-y","url":null,"abstract":"<div><p>This study investigates the correlation and phase relationships between chromospheric Ca <span>ii</span> K plage areas and key solar activity indices—including sunspot number, sunspot area, and 10.7 cm radio flux—across Solar Cycles 14 – 22. Using homogenized data from the Kodaikanal Solar Observatory, we demonstrate robust correlations (r &gt; 0.85) across all parameters and confirm that plage areas adhere to the Gnevyshev-Ohl rule and exhibit Gnevyshev gaps during several cycle maxima. Through Morlet wavelet analysis and wavelet coherence (WTC), we identify significant intermediate-term quasi-periodicities, specifically Rieger-type periods (130 – 190 days) and quasi-biennial oscillations (QBOs; 1 – 4 years). While these signals show notable cycle-to-cycle variability and frequent phase asynchrony at intermediate scales, a stable phase synchrony persists within the fundamental 9 – 12 year periodicity belt, indicating a tightly coupled decadal evolution of chromospheric and photospheric magnetic manifestations. These results, which align with theories of tachocline instabilities and magnetic Rossby waves, provide critical empirical constraints for solar dynamo models and enhance our understanding of the long-term evolution of the Sun’s multi-layered magnetic environment.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 10","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149072445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Space-Weather Utilities for Research and Forecasting (SURF): A Tool for Investigating Hydrodynamic Aspects of Solar Wind and Coronal Mass Ejection Expansion and Evolution","authors":"Mathew J. Owens,&nbsp;Luke A. Barnard","doi":"10.1007/s11207-026-02738-7","DOIUrl":"10.1007/s11207-026-02738-7","url":null,"abstract":"<div><p>We introduce Space-weather Utilities for Research and Forecasting (SURF), a flexible modelling framework for reconstructing and forecasting large-scale solar wind structure. SURF incorporates both the reduced hydrodynamic “HUXt” model and a newly developed one-dimensional, hydrodynamic solver, “hydro.”. The new solver introduces more physically consistent compression effects, while retaining the computational efficiency required for ensemble forecasting, uncertainty quantification, and large parametric studies. SURF-hydro solves the 1D Euler equations in spherical geometry using finite-volume methods with Riemann solvers and second-order spatial reconstruction. It is shown to accurately reproduce an analytical solution to pressure-driven expansion of a uniform spherical solar wind. Using 30 years of near-Earth OMNI observations, we derive empirical relations between speed, density, and temperature at 1 AU and map these back to 0.1 AU to provide non-equilibrium inner-boundary conditions for SURF-hydro (and for use with other solar wind models). This approach produces more realistic solar wind speed, density and temperature values and variability at 1 AU than simulations based on equilibrium thermodynamic relations at 0.1 AU. While magnetic pressure and tension forces are not included, SURF-hydro is also shown to reproduce the key features of coronal mass ejection (CME) expansion and evolution. For one particular example of a structured solar wind, sensitivity tests demonstrate that CME density and temperature at 0.1 AU alter 1 AU transit times and arrival speeds by 15 – 20%, highlighting a potential under-explored source of forecast uncertainty. SURF-hydro therefore provides a computationally efficient bridge between idealised models and full 3D magnetohydrodynamic simulations, enabling systematic investigation of boundary condition assumptions and CME parameter sensitivity for both research and operational space-weather forecasting.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13619770/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149079375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Supersonic Flows Observed by THEMIS Related to a Coronal Bright Point and Filament","authors":"Garima Karki,&nbsp;Brigitte Schmieder,&nbsp;Ramesh Chandra,&nbsp;Pooja Devi,&nbsp;Pascal Démoulin,&nbsp;Stefaan Poedts","doi":"10.1007/s11207-026-02744-9","DOIUrl":"10.1007/s11207-026-02744-9","url":null,"abstract":"<div><p>In this paper, we report on the dynamics of the fine structure of a solar quiescent filament observed on September 28, 2023, with the Télescope Héliographique pour l’Etude du Magnétisme et des Instabilités Solaires (THEMIS). The main aim is to understand the relationship between the supersonic downflows measured in H<span>(alpha )</span> at the filament end and an associated coronal bright point. We use a cloud-model method to derive the supersonic velocity of the falling, elongated cool blob. Besides, we use H<span>(alpha )</span> Global Oscillation Network Group (GONG) data to track the plasma along the filament. Repetitive plasma motions are observed along the northern end of the filament. During one event of plasma motion, the THEMIS field of view was centred on the filament end, where supersonic downflows of 89.8 km s⁻¹ were measured with a standard deviation of ± 0.25 km s⁻¹. We suggest that the plasma moving along the filament could be falling towards the chromosphere. A ballistic trajectory could confirm this first scenario. However, we could not rule out the second scenario, in which coronal rain forms due to the thermal instability of coronal plasma. In the hot AIA channels, we identify a bright point at the same location, with a temperature reaching about 6 MK. In addition, we confirm a counter-streaming flow pattern along the fine filament strands, with widths of less than an arc second, as measured by the high-spatial- and spectral-resolution spectra of THEMIS.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149133044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-Lane Type II Radio Bursts: Insights into Shock Propagation in the Corona","authors":"Nadiya K.,&nbsp;Divya Paliwal,&nbsp;Anshu Kumari","doi":"10.1007/s11207-026-02728-9","DOIUrl":"10.1007/s11207-026-02728-9","url":null,"abstract":"<div><p>Type II solar radio bursts are considered as the signatures of the coronal shocks. These bursts are generated from plasma waves excited by magnetohydrodynamic (MHD) shocks, and then converted into radio waves at the local plasma frequency and/or its harmonics. Hence, these bursts often have fundamental-harmonic (FH) and band-splitting (SB) structures, which provide insights into shock generation and propagation in the corona, hence, in turn, the corresponding coronal conditions. In the present study, we analysed an unusual multi-lane type II burst observed with ground-based solar radio spectrographs on May 29, 2024, between 14:24 and 14:43 UT. The start and end frequencies of the type II burst were 450 MHz and 25 MHz, respectively. By combining spectral information with radio imaging data, we found that radio waves were escaping from the corona via emissions from distinct shock regions. In addition, along with the traditional FH and SB, there were multi-lane structures in the type II bursts. Our analysis suggests complex, inhomogeneous shock dynamics near the leading edge (LE) of the coronal mass ejection (CME). This indicates that the plasma material compresses more strongly in these forefront regions. This was confirmed by radio imaging observations, which showed that the higher-frequency emission occurred at a higher altitude than the lower-frequency emission. Our results suggest that the shock geometry and plasma inhomogeneity play an important role in the generation of type II bursts, leading to traditional fundamental-harmonic split-band (FH-SB) pairs with additional splitting in the type II bands.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149034944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of X-ray Solar Flare Rates from 1976 to 2025","authors":"Owen Giersch","doi":"10.1007/s11207-026-02743-w","DOIUrl":"10.1007/s11207-026-02743-w","url":null,"abstract":"<div><p>A statistical analysis was performed on solar x-ray flares of M class and higher to determine the variation in flare intensity distribution and flare rates across solar cycles. Firstly, flares were binned into intensity categories and compared across sunspot cycles. Secondly, flare rates by the flaring region’s McIntosh class were compared across sunspot cycles. Generally, the flare intensity distribution between adjacent solar cycles can be considered similar at the 95% confidence interval, but all cycles show significant differences between the flare rates by sunspot group classification. It is unclear if the reason for this difference is due to observer bias or to a more fundamental physical reason.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-026-02743-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149034542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physics-Constrained Reconstructions of Sunspot Number from Millennial-Scale Annual Heliospheric Modulation Potential","authors":"Chitradeep Saha,&nbsp;Mathew Owens,&nbsp;Mike Lockwood,&nbsp;Luke Barnard,&nbsp;Nicolas Brehm,&nbsp;Silvia Dalla,&nbsp;Konstantin Herbst,&nbsp;Raimund Muscheler,&nbsp;Jian Wang","doi":"10.1007/s11207-026-02731-0","DOIUrl":"10.1007/s11207-026-02731-0","url":null,"abstract":"<div><p>Long-term solar magnetic variability governs the space climate conditions. These variations also modulate the galactic cosmic ray influx reaching Earth and subsequently regulate the production of cosmogenic isotopes in Earth’s atmosphere. By harnessing the multi-millennial records of the abundances of these radio-isotopes stored in natural terrestrial reservoirs, such as tree wood and ice sheets, it is possible to reconstruct past solar magnetic activity predating the telescopic era. However, existing regression-based reconstruction methods using isotope data from time series extracted from the reservoirs are often applied to conditions outside the valid parameter range. This can result in a number of problems, including negative sunspot numbers during low solar activity phases, which correspond to statistically permissible extrapolation artefacts but have no physical meaning. To address this, we developed a Monte-Carlo inversion framework consisting of a sequence of physics-based semi-empirical forward models, supplemented by an Approximate Bayesian Computation-based posterior selection, to infer the most plausible temporal evolution of solar magnetic parameters. Our approach produces physically consistent, uncertainty-quantified reconstructions of annually resolved parameters, including sunspot numbers. We apply the method to two modulation potential datasets, namely geomagnetic record from 1845 – 2020, and an annual ¹⁴C estimate over the period 971 – 1932. Our new reconstruction method is designed to yield strictly non-negative sunspot numbers and shows close agreement with direct observations within uncertainty during the telescopic era. These results offer valuable insights into long-term solar variability and provide improved constraints for long-term solar dynamo modelling. The annual-scale reconstructions are also directly usable for solar irradiance estimation, terrestrial climate modelling, and studies of long-term Sun-Earth coupling.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-026-02731-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-Driven Segmentation of Solar Filaments Based on Ground-Based Instrument Data","authors":"Oleg Stepanyuk,&nbsp;Werner Pötzi,&nbsp;Momchil Dechev,&nbsp;Rositsa Miteva,&nbsp;Kamen Kozarev","doi":"10.1007/s11207-026-02741-y","DOIUrl":"10.1007/s11207-026-02741-y","url":null,"abstract":"<div><p>The dynamic behavior of solar prominences and filaments is a precursor to coronal mass ejections (CMEs), which can disrupt Earth’s magnetosphere and affect satellite communications. Systematic ground-based solar observations, conducted with high temporal resolution, are instrumental in monitoring these structures. Analysis of the morphological changes and destabilization processes of filaments and prominences captured in datasets can help identify early warning signs of potential eruptions. This capability is vital for developing reliable space weather forecasting systems, thereby mitigating the adverse effects of solar disturbances on Earth’s technological infrastructure. Previously, we introduced hybrid algorithmic-data driven method which performance was shown on a set of Solar Dynamic Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument data performing segmentation of extreme ultraviolet (EUV) and shock waves. In this work, we extend certain aspects of this approach to image segmentation of solar features – filaments and prominences using H<span>(alpha )</span> Kanzelhöhe Observatory data. We describe a leakage-aware, sparse multi-year sampling strategy. We present image segmentation models pre-trained on synoptic and normalized image data, followed by a discussion of how model performance depends on training-set engineering, data preprocessing techniques, and the choice of loss metrics. We perform a limited study, both analytically and numerically, of the effect of external, fixed normalization versus native input for compact U-Net-based segmentation of solar H<span>(alpha )</span> filaments, also contributing to ongoing research on normalization in deep networks in general and compact models in particular.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracking Solar Energetic Electrons from Corona to 1 AU: A Multi-Spacecraft Study of the 28 January 2025 Event","authors":"Shiwei Feng,&nbsp;Xinhua Zhao,&nbsp;Nanbin Xiang,&nbsp;Shiyang Qi,&nbsp;Wei Wang,&nbsp;Xingyao Chen,&nbsp;Linjie Chen,&nbsp;Zhichao Zhou,&nbsp;Alexey Kuznetsov,&nbsp;Yihua Yan","doi":"10.1007/s11207-026-02730-1","DOIUrl":"10.1007/s11207-026-02730-1","url":null,"abstract":"<div><p>We report and analyze a solar energetic electron (SEE) event on January 28, 2025, associated with an extreme ultraviolet (EUV) jet and accompanied by type III and type II radio bursts. Combining multi-viewpoint in situ and remote-sensing observations with modeling, we trace the propagation of energetic electrons from the corona to interplanetary space across time, space, and energy. Potential Field Source Surface (PFSS) reconstruction shows that coronal type III burst sources and the EUV jet ejection direction generally align with open magnetic field lines. Time Difference of Arrival (TDOA) localization indicates that the interplanetary type III burst source lies along the Parker spiral leading to Wind, with electron-beam velocities of 0.06c – 0.17c. Velocity Dispersion Analysis (VDA) of electrons detected by three spacecraft near 1 AU yields solar release times of 08:03 – 08:23 UT for Solar TErrestrial RElations Observatory-Ahead (STEREO-A) and 08:07 – 08:27 UT for Wind, with derived path lengths of <span>(1.2 pm 0.9)</span> AU and <span>(2.6 pm 1.6)</span> AU, respectively. The path length for Wind exceeds the nominal Parker spiral length, suggesting a complex, non-ideal interplanetary magnetic field topology. This study presents a methodology for tracking SEEs from their source to interplanetary observers, providing observational constraints for space weather forecasting models. We also infer that the locally observed SEEs and the electron beams that excite interplanetary type III bursts may not be the same population, based on differences in their release and arrival times.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cycle Variation in the Occurrence of Great Soft X-ray Solar Flares","authors":"V. N. Obridko,&nbsp;M. M. Katsova,&nbsp;D. D. Sokoloff","doi":"10.1007/s11207-026-02732-z","DOIUrl":"10.1007/s11207-026-02732-z","url":null,"abstract":"<div><p>Powerful nonstationary processes such as flares and coronal mass ejections are detected mainly near the solar cycle maxima. However, the analysis of the great flares since 1975, when the GOES monitoring started, leads us to more precise conclusions. We have traced the latitudinal distribution of X-class flares and their dependence on the phase of the cycle throughout four cycles. Besides, we compared directly their positions with the magnetic field structure. It was found that the relatively weak X4 to X7 class flares occur at relatively high latitudes (15 – 20 degrees), where two waves of activity converge, one moving toward the equator and the other, the wave of the following cycle, directed poleward. Such events are observed almost constantly 1 – 2 years before the cycle maximum. At the same time, the number of the powerful X-ray flares increases sharply during the maximum phase, but the greatest X10 class flares are observed at the beginning of the declining phase, where wave interactions still persist, and throughout the decline phase. Note that they are virtually absent during the cycle growth phase. Thus, we conclude that the greatest X-ray flares begin to appear 1 – 2 years before the maximum number of sunspots in the overlapping phase, when different kinds of activity waves coexist on the Sun at relatively high latitudes, and, then, continue to appear at the boundary, which separates the wave of local fields and the poleward wave of the following cycle.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cross-Helicity and Chaotic Dynamics of Full-Disc Solar Magnetic Field","authors":"Alexander Bershadskii","doi":"10.1007/s11207-026-02725-y","DOIUrl":"10.1007/s11207-026-02725-y","url":null,"abstract":"<div><p>Using the results of laboratory experiments and direct numerical simulations, as well as observations of the full-disc solar magnetic field and sunspot number dynamics, it is demonstrated that cross-helicity can dominate the decaying part of the frequency power spectra of the magnetic field generated by a magnetohydrodynamic (MHD) dynamo in chaotic/turbulent swirling flows for sufficiently strong MHD turbulence (including the solar dynamo). The theoretical consideration is based on a Kolmogorov-like phenomenology within the framework of the distributed chaos concept. It is also shown that the solar full-disc magnetic field for the last two solar cycles with weak magnetic activity exhibits deterministic chaotic behavior concentrated around the equator.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"301 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}