Solar Physics最新文献

{"title":"Direct Observational Evidence of Solar Wind Density Controlling the Evolution of the Ring Current During the 2024 October Major Storm","authors":"Ming-Xian Zhao,&nbsp;Gui-Ming Le","doi":"10.1007/s11207-025-02539-4","DOIUrl":"10.1007/s11207-025-02539-4","url":null,"abstract":"<div><p>We investigated the interplanetary source of the October 2024 major storm and determined that it was triggered by a sheath region and a magnetic cloud (MC), with the sheath region playing a decisive role. The MC has a larger and longer duration of southward interplanetary magnetic field (IMF) and solar wind electric field compared to the sheath, and the largest southward IMF and solar wind electric field were observed within the MC. As expect, the solar wind density in the sheath region is much larger than that in the MC. The results of this study not only provide direct evidence that solar wind density controls the evolution of the ring current, but also demonstrate that the correlation coefficients between the largest southward IMF and geomagnetic storm intensity, as well as between the largest solar wind electric field and geomagnetic storm intensity, lack physical meaning. The contribution of the sheath region to the intensity of the major storm, as estimated by the empirical formula developed by Burton, McPherron, and Russell (1975) (hereafter referred to as the BMR equation), was found to be smaller than that of the MC. However, actual observations indicate the opposite. This discrepancy suggests that the BMR equation is not capable of accurately estimating the ring current variation. The injection term in the BMR equation is merely a linear function of the solar wind electric field, without considering the solar wind density. This indicates that if we overlook the influence of solar wind density on the evolution of the ring current, estimating the intensity of a geomagnetic storm based solely on the integral of the solar wind electric field during the main phase of the storm would yield incorrect results. The October 2024 major storm also provides direct evidence that solar wind velocity, density, and the southward component of the IMF are all important parameters in the evolution of the ring current.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934652","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":"Recovery of the Solar Cycle from Maunder-Like Grand Minima Episodes: A Quantification of the Necessary Polar Flux Threshold Through Solar Dynamo Simulations","authors":"Chitradeep Saha,&nbsp;Sanghita Chandra,&nbsp;Dibyendu Nandy","doi":"10.1007/s11207-025-02538-5","DOIUrl":"10.1007/s11207-025-02538-5","url":null,"abstract":"<div><p>The 11-yr cycle of sunspots undergoes amplitude modulation over longer timescales. As a part of this long-term modulation in solar activity, the decennial rhythm occasionally breaks, with quiescent phases with very few sunspots observed over multiple decades. These episodes are termed as solar grand minima. Observation of solar magnetic activity proxies complemented by solar dynamo simulations suggests that the large-scale solar polar fields become very weak during these minima phases with a temporary halt in the polar field reversal. Eventually, with the accumulation of sufficient polar fluxes, the polarity reversal and regular cyclic activity is thought to resume, Using multi-millennial dynamo simulations with stochastic forcing, we quantify the polar flux threshold necessary to recover global solar polarity reversal and surmount grand minima phases. We find that the duration of a grand minimum is independent of the onset rate and does not affect the recovery rate. Our results suggest a method to forecast the Sun’s recovery from a grand minima phase. However, based on our approach, we could not identify specific precursors that signal entry in to a grand minima phase – implying that predicting the onset of grand minima remains an outstanding challenge.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934651","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":"Correlation of Coronal Hole Area Indices and Solar Wind Speed","authors":"Egor Illarionov,&nbsp;Andrey Tlatov,&nbsp;Ivan Berezin,&nbsp;Nadezhda Skorbezh","doi":"10.1007/s11207-025-02530-z","DOIUrl":"10.1007/s11207-025-02530-z","url":null,"abstract":"<div><p>Coronal holes (CHs) are widely considered as the main sources of high-speed solar wind streams. We validate this thesis comparing the smoothed time series of solar wind speed measured by the Advanced Composition Explorer (ACE) and various indices of CH areas constructed from the CH catalog compiled at the Kislovodsk Mountain Astronomical Station for the period 2010 – 2025. The main result is that we find specific indices of CH areas that give a strong correlation with smoothed solar wind speed variations. As an example, 1-year averaged areas of CHs located within 30 degrees of the solar equator yield a correlation of 0.9 with 1-year averaged solar wind speed. This strong correlation is a feature of the particular CH catalog, and considering an alternative CH catalog obtained using the Spatial Possibilistic Clustering Algorithm (SPoCA) from the Heliophysics Event Knowledgebase (HEK), the same index provides a correlation of only 0.3. Although the fact that the correlation significantly depends on the catalog requires a separate discussion, we conclude that if some of the catalogs can be used to construct a reliable indicator of solar wind speed variations, then this methodology should be maintained further. Additionally, we present time-latitude diagrams of rolling correlation between CH areas and solar wind speed, which, in our opinion, can be used to reveal source CHs for high-speed solar wind streams.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144929226","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":"Statistical Analysis of Sunspot Area and Magnetic Flux on Solar Disc During 2011 – 2023","authors":"Avneesh Kumar,&nbsp;Nagendra Kumar,&nbsp;Hari Om Vats","doi":"10.1007/s11207-025-02537-6","DOIUrl":"10.1007/s11207-025-02537-6","url":null,"abstract":"<div><p>We investigate the temporal variations and distribution functions of daily sunspot area and magnetic flux data from 2011 to 2023. The yearly distribution of sunspot area on the solar full disc, southern hemisphere and northern hemisphere, and magnetic flux on the solar full disc are positively skewed for all the years from 2011 to 2023. We analyzed the variations of yearly maximum, median, first quartile, third quartile, interquartile range and mean of the daily sunspot area and magnetic flux on the solar full disc and found their maxima and minima for sunspot area and magnetic flux. Maxima occur in the years 2014 and 2015 for sunspot area and magnetic flux, respectively, whereas their minima occur in the years 2018 and 2019. We found the correlations between the descriptive statistical measures of sunspot area and magnetic flux, kernel density estimator, and lognormal functions to describe the distributions of daily sunspot area and magnetic flux. We found a positive correlation of 0.96 between the distribution functions of sunspot area and magnetic flux on the solar full disc during 2011 – 2023. We demonstrated that the distribution function for daily sunspot area correlates linearly well with the distribution function for magnetic flux during 2011 – 2023.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144923093","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":"Statistical Analysis of Solar Flare Properties from 1975 to 2017","authors":"L. Biasiotti,&nbsp;S. L. Ivanovski","doi":"10.1007/s11207-025-02532-x","DOIUrl":"10.1007/s11207-025-02532-x","url":null,"abstract":"<div><p>The statistical analysis of solar flares is essential for understanding their characteristics and properties, serving as a fundamental tool to interpret flare distributions and constrain the physical mechanisms driving their occurrence. In this paper, we investigated the statistical properties of these energetic phenomena over the last four solar cycles, spanning the period from September 1975 to June 2017. Specifically, we analysed the temporal (i.e., waiting time and duration) and energetic (i.e., peak intensity) aspects of soft X-ray (SXR) flares from the GOES catalogue in terms of flare occurrence rates and frequency distributions. We found that (i) the duration of most of the events increases with the increase of the intensity of a given flare, i.e. with its class. X-class flares exhibit a second peak centred around the 80th minute after its formation. (ii) Waiting times, i.e. the interval between the starting time of two consecutive flares, correlate with the solar activity variation within the solar cycle. (iii) In all solar cycles considered here, the flare and CME waiting-time distributions (WTDs) show similar power-law indices of the frequency event distribution and time variation, especially in the tail of the power-law distribution. (iv) Peak-intensity energy does not correlate with the waiting time, contrary to the idea that the more time elapses between two consecutive events the higher the intensity of the flare is.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-025-02532-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144905255","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":"Synthetic Resonance and Thomson Scattering of a Chromospheric (text{Ly}alpha ) Profile Using the Bastille Day CME Model Corona: Part 1","authors":"Nelson Reginald,&nbsp;Lutz Rastaetter","doi":"10.1007/s11207-025-02529-6","DOIUrl":"10.1007/s11207-025-02529-6","url":null,"abstract":"<div><p>In this article, Part 1, we have synthetically resonance scattered and Thomson scattered a measured solar chromospheric <span>(mathrm{Ly}alpha )</span> spectral radiance (CLSR) spectrum off the neutral hydrogen [<span>(N_{1})</span>] atoms in ground state and free electrons [<span>(N_{mathrm{e}})</span>], respectively, contained in a 3D coronal model of the 14 July 2000 (“Bastille Day”) <i>Coronal Mass Ejection</i> (CME). From these two scatters, we have computed maps of the associated resonance scattered spectral radiance (RSSR) spectrum and the Thomson scattered spectral radiance (TSSR) spectrum in ultraviolet (UV) from 121.3 to 121.8 nm with a wavelength resolution of 0.1 nm, which encompasses the <span>(mathrm{Ly}alpha )</span> center line at 121.57 nm. We then integrated the maps over the above wavelength range and have created two 2D resonance scattered radiance (RSR) and Thomson scattered radiance (TSR) maps. As expected, the TSSR spectrum is <span>(approx 1000)</span> times dimmer than the RSSR spectrum, which we can deem for it to contribute towards noise in the center of the RSSR spectrum. In a follow up article, Part 2, we intend to do the following with these maps. First, we will use the computed RSSR spectra along each line of sight (LOS) to derive the proton temperature [<span>(T_{mathrm{p}})</span>] and speed [<span>(V_{mathrm{p}})</span>] using the Doppler Dimming technique (DDT). Second, we will compare these derived proton parameters along each LOS with the actual values contained within the Bastille Day CME model at the plane of the sky and compute the differences. If we find they are different we will then determine where along the LOS they closely match and their distances from the plane of the sky. Finally, we will quantify an estimate of the systematic error from using DDT to measure the proton parameters at the plane of the sky, which is different from the statistical error margins reported in the literature from real RSSR experiments conducted from space-based instruments.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144894024","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":"Multispacecraft Observations of the 2024 September 9 Backside Solar Eruption That Resulted in a Sustained Gamma Ray Emission Event","authors":"Nat Gopalswamy,&nbsp;Pertti Mäkelä,&nbsp;Sachiko Akiyama,&nbsp;Hong Xie,&nbsp;Seiji Yashiro,&nbsp;Stuart D. Bale,&nbsp;Robert F. Wimmer-Schweingruber,&nbsp;Patrick Kühl,&nbsp;Säm Krucker","doi":"10.1007/s11207-025-02526-9","DOIUrl":"10.1007/s11207-025-02526-9","url":null,"abstract":"<div><p>We report on the 2024 September 9 sustained gamma-ray emission (SGRE) event observed by the Large Area Telescope (LAT) on board the Fermi satellite. The hevent was associated with a backside solar eruption observed by multiple spacecraft such as the Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO), Parker Solar Probe (PSP), Solar Orbiter (SolO), Solar Dynamics Observatory (SDO), Wind, and GOES, and by ground-based radio telescopes. Fermi/LAT observed the SGRE after the EUV wave from the backside eruption crossed the limb to the frontside of the Sun. SolO’s Spectrometer Telescope for Imaging X-rays (STIX) imaged an intense (X3.3) flare, which occurred ≈ 41° behind the east limb, from heliographic coordinates S13E131. Forward modeling of the coronal mass ejection (CME) flux rope revealed that it impulsively accelerated (3.54 km s⁻²) to attain a peak speed of 2162 km s⁻¹. SolO’s energetic particle detectors (EPD) observed protons up to ≈ 1 GeV from the extended shock and electrons that produced a complex type II burst and possibly type III bursts. The durations of SGRE and type II burst are consistent with the linear relation between these quantities obtained from longer duration (&gt; 3 hours) SGRE events. All these observations are consistent with an extended shock surrounding the CME flux rope, which is the likely source of high-energy protons required for the SGRE event. We compare this event with six other behind-the-limb (BTL) SGRE eruptions and find that they are all consistent with energetic shock-driving CMEs. We also find a significant east-west asymmetry (3:1) in the BTL source locations.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-025-02526-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144894025","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":"An Analysis of the Solar Differential Rotation in Solar Cycle No. 19 (1954 – 1964) Determined Using Kanzelhöhe Sunspot Group Positions","authors":"Ivana Poljančić Beljan,&nbsp;Luka Šibenik,&nbsp;Tomislav Jurkić,&nbsp;Klaudija Lončarić,&nbsp;Rajka Jurdana-Šepić,&nbsp;Damir Hržina,&nbsp;Werner Pötzi,&nbsp;Roman Brajša,&nbsp;Astrid M. Veronig,&nbsp;Arnold Hanslmeier","doi":"10.1007/s11207-025-02528-7","DOIUrl":"10.1007/s11207-025-02528-7","url":null,"abstract":"<div><p>We study solar differential rotation for solar cycle No. 19 (1954 – 1964) by tracing sunspot groups on the sunspot drawings of Kanzelhöhe Observatory for Solar and Environmental Research (KSO). Our aim is to extend previous differential rotation (DR) analysis from the KSO data (1964 – 2016) to the years prior to 1964 to create a catalog of sunspot group positions and photospheric DR parameters from KSO sunspot drawings and white light images. Synodic angular rotation velocities were first determined using the daily shift (DS) and robust linear least-squares fit (rLSQ) methods, then converted to sidereal velocities, and subsequently used to derive solar DR parameters. We compare the DR parameters obtained from different sources and analyse the north–south asymmetry of rotation for solar cycle No. 19. It has been shown that our results for the equatorial rotation velocity (parameter <span>(A)</span>) and the gradient of DR (parameter <span>(B)</span>) coincide with earlier results from the KSO data (performed with a different method), as well as with results from the Kodaikanal Solar Observatory (KoSO) and the Yunnan Observatories (YNAO). In contrast, the values of parameter <span>(A)</span> from three different earlier studies based on the Greenwich Photoheliographic Results (GPR) exhibit statistically significant differences when compared to the values of parameter <span>(A)</span> derived from KSO, KoSO and YNAO. These findings suggest that the GPR data have the largest inconsistency compared to the other three data sources, highlighting the need for further analysis to identify the causes of these discrepancies. The analysis of the north-south asymmetry in the solar rotation profile using two different methods shows that the DR parameters of the hemispheres coincide, indicating a rotational symmetry around the equator. This is consistent with previous results from KSO and YNAO data. However, all sources indicate slightly higher equatorial rotation velocities in the southern hemisphere.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144888106","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":"Data-Driven Reconstruction of a Low-Order Dynamo Model from Sunspot Data","authors":"Alfio Bonanno,&nbsp;Rainer Arlt","doi":"10.1007/s11207-025-02531-y","DOIUrl":"10.1007/s11207-025-02531-y","url":null,"abstract":"<div><p>Understanding the long-term variability of the solar dynamo remains a key challenge in solar physics. In this work, we apply the Sparse Identification of Nonlinear Dynamical Systems (SINDy) framework to reconstruct a low-order dynamo model directly from 275 years of sunspot number data. Our data-driven approach for discovering governing equations from time series enables us to identify a minimal yet accurate dynamical system that captures the essential features of solar activity cycles. We demonstrate that, when interpreted as a low-order dynamo model, the solar dynamo is governed by an unstable saddle point, with nonlinear evolution leading to cyclic behavior. In particular we find that the underlying dynamics is described by a cubic nonlinearity driven by a <span>(B_{phi }dot{B}_{phi }^{2})</span> term, which results in a phase space not necessarily of the Van der Pol universality class. Additionally, we show that higher-order nonlinearities are disfavored, and we discuss how to interpret our findings in terms of a mean-field dynamo model with a novel quenching term.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-025-02531-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144868825","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":"Toward a Consensus for Multi-Sourced Photospheric Line-of-Sight Magnetic Field Cross-Calibration","authors":"Yang Liu,&nbsp;Jon Todd Hoeksema,&nbsp;Luca Bertello,&nbsp;Gordon Petrie,&nbsp;Alexei Pevtsov","doi":"10.1007/s11207-025-02523-y","DOIUrl":"10.1007/s11207-025-02523-y","url":null,"abstract":"<div><p>In this work we compare the full-disk line-of-sight magnetic field measurements of the Helioseismic and Magnetic Imager (HMI) with the magnetograms from multiple sources including the Global Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI), the Synoptic Optical Long-term Investigations of the Sun (SOLIS) instrument, the Mount Wilson Observatory (MWO), and the Wilcox Solar Observatory (WSO). A scaling factor is then derived that matches the magnetograms from these instruments to those of HMI. The scaling factors are <span>(1.438pm 0.000)</span> for GONG, <span>(0.701pm 0.001)</span> for MDI, <span>(1.038pm 0.001)</span> for SOLIS, <span>(2.795pm 0.002)</span> for MWO, and <span>({3.582pm 0.006})</span> for WSO. This scaling factor varies with the center-to-limb distance and field strength. Distortion maps for these instruments are also determined using the HMI data as a reference.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144868909","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}