Solar PhysicsPub Date : 2025-07-30DOI: 10.1007/s11207-025-02520-1
Shiwei Feng, Pietro Zucca
{"title":"Multiple Sources of a Type II Radio Burst Within a Coronal Mass Ejection","authors":"Shiwei Feng, Pietro Zucca","doi":"10.1007/s11207-025-02520-1","DOIUrl":"10.1007/s11207-025-02520-1","url":null,"abstract":"<div><p>Solar type II radio bursts are generated through plasma emission caused by energetic electrons that are accelerated by shock waves during solar eruptions. These bursts serve as tracers of shock waves in the corona. However, the complexity of solar eruptions and the lack of radio imaging observations have hampered our understanding of type II bursts. The newly built Daocheng Solar Radio Telescope (DSRT) detected a rare type II burst. Its harmonic shows an initial herringbone (HB), followed by three nearly parallel lanes. These lanes form a framed pattern: a central main lane (termed MAIN) with a higher brightness temperature and wider bandwidth, flanked by two well-defined fringes, F1 and F2. Radio and extreme ultraviolet imaging observations indicate that the sources of the HB are precisely located on the flank of the leading shock wave driven by a coronal mass ejection (CME). In contrast, the MAIN and F2 sources correlate in terms of time, location, electron number density, and propagation velocity with an ascending coronal loop. In contrast, the F1 sources are associated with a nearby but distinct coronal loop. These observations suggest that at least three sources of the type II burst accompany the CME. A scenario involving multiple shock waves within the CME is proposed to explain the presence of the different radio sources.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145171323","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":"Differential Rotation of Long-Lived Sunspot Groups in Solar Cycles 22 – 24 Determined by Watukosek Solar Observatory Data","authors":"Nanang Widodo, Johan Muhamad, Ayu Dyah Pangestu, Gerhana Puannandra Putri, Santi Sulistiani, Silmie Vidiya Fani, Tiar Dani, Dhani Herdiwijaya","doi":"10.1007/s11207-025-02516-x","DOIUrl":"10.1007/s11207-025-02516-x","url":null,"abstract":"<div><p>Solar differential rotation (SDR) profile can give an important clue on how the solar dynamo varies from one solar cycle to another. In order to investigate the variability of SDR across multiple solar cycles, we calculated rotation rates of sunspots observed in Solar Cycles 22 – 24 (1987 – 2019) by using sunspot data records from the Watukosek Solar Observatory (WKSO). WKSO has the longest continuous sunspot observation record in Indonesia. Its historical record of sunspot observations provides a unique and valuable dataset for solar physics research. In this paper, we introduced the repository of sunspot observations from WKSO for almost three solar cycles. Using these data, we calculated the rotation rate of each long-lived sunspot group during Solar Cycles 22 – 24 by measuring the linear least-square fitting of daily movements of the sunspot position in various latitudes. The results confirm the well-established pattern of SDR, with a faster rotation at the equator compared to higher latitudes. We also found that the rotation rates of long-lived sunspot groups are slower than the differential rotation rates derived from the entire sunspot data. Furthermore, our analysis of this dataset confirmed that the bipolar sunspot groups rotate faster than unipolar sunspots. These results suggest that unipolar and bipolar sunspots are anchored at different depths beneath the solar surface. These findings are consistent with prior results using older data from different observatories, suggesting the reliability and scientific importance of the sunspot observations from WKSO for understanding solar-dynamo processes and their variability.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145171321","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}
Solar PhysicsPub Date : 2025-07-29DOI: 10.1007/s11207-025-02517-w
Mariano Poisson, Pascal Démoulin, Marcelo López Fuentes, Cristina H. Mandrini
{"title":"Bayesian Modeling of Emerging Bipolar Active Regions from Solar Cycle 23","authors":"Mariano Poisson, Pascal Démoulin, Marcelo López Fuentes, Cristina H. Mandrini","doi":"10.1007/s11207-025-02517-w","DOIUrl":"10.1007/s11207-025-02517-w","url":null,"abstract":"<div><p>Active regions (ARs) are the photospheric manifestations of emerging magnetic flux ropes (FRs) formed in the solar interior. We analyze the emergence of 126 bipolar ARs during Solar Cycle 23 using a flux rope model, whose parameters are inferred through a Bayesian inference method. This approach allows us to estimate key sub-photospheric properties of FRs. We find that the Bayesian method effectively captures the global magnetic characteristics of ARs, with discrepancies primarily arising in the later stages of emergence. We examine the ability of a flux-balanced FR model with a symmetric circular cross-section to reproduce polarity shapes during these late stages. Additionally, we analyze how the inclination of the FR legs provides insight into the emergence stage. We propose an improved method for estimating the separation of polarities, which decreases projection effects and flux distribution biases. Furthermore, we confirm a strong correlation between the AR flux and the distance between the main polarities, as well as the evolution of their separation speed. Finally, we identify a characteristic ratio between the thickness of the FR and its curvature radius, suggesting an underlying physical mechanism governing this ratio.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145171163","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}
Solar PhysicsPub Date : 2025-07-24DOI: 10.1007/s11207-025-02514-z
Wei Liu, Haoxiang Wang, Zhe Zhang, Dengyi Chen, Yan Zhang, Yang Su, Wei Chen, Zhentong Li, Xiankai Jiang, Qiang Wan, Yiming Hu, Yu Huang
{"title":"On-Orbit Performance Analysis of the Hard X-ray Imager (HXI) on the Advanced Space-Based Solar Observatory (ASO-S)","authors":"Wei Liu, Haoxiang Wang, Zhe Zhang, Dengyi Chen, Yan Zhang, Yang Su, Wei Chen, Zhentong Li, Xiankai Jiang, Qiang Wan, Yiming Hu, Yu Huang","doi":"10.1007/s11207-025-02514-z","DOIUrl":"10.1007/s11207-025-02514-z","url":null,"abstract":"<div><p>This study presents a detailed on-orbit performance analysis of the Hard X-ray Imager (HXI) aboard the Advanced Space-based Solar Observatory (ASO-S), confirming its overall stability within design specifications for key parameters like detection efficiency and energy resolution. However, the analysis focuses primarily on characterizing temporal variations, including distinct periodic fluctuations linked to orbital (∼ 99 minutes) and annual cycles, as well as non-periodic events. Temperature variations highlight orbital/seasonal effects and suggest potential long-term thermal leakage around the Solar Aspect System (SAS) via a gradual rise on the front plate. High-voltage (HV) remains stable during nominal operations, but its management during South Atlantic Anomaly (SAA) passages is critical. Gain analysis identifies a generally stable trend punctuated by five significant abrupt decreases attributed to operational parameter reset errors and radiation exposure during SAA passages (influenced by geomagnetic storms or operational choices). Detection efficiency and energy resolution remained largely stable, with notable deviations primarily linked to the parameter reset error. These findings demonstrate the instrument’s general robustness while highlighting specific anomalies and underscoring the need for ongoing monitoring, optimized operational protocols (especially HV management), and time-dependent calibration to ensure the highest data quality for solar flare science.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145168043","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}
Solar PhysicsPub Date : 2025-07-22DOI: 10.1007/s11207-025-02506-z
Robin Colaninno, Arnaud Thernisien, Russell Howard, David Brechbiel, Hillary Dennison, Phillip Hess, Stephen Koss, Mario Noya, Wayne Simon, Alena Thompson, Donald McMullin, Sophie Laut, Tonia Hunt, Larry Gardner, Andrew Lanagan, Robert Hagood, Bruce Hohl, Andrew Uhl, Linda Smith, Dallas Zurcher, Eloise Stump, Miles Newman, Tai Ragan, James Caron
{"title":"The Narrow Field Imager (NFI) for the Polarimeter to Unify the Corona and Heliosphere (PUNCH)","authors":"Robin Colaninno, Arnaud Thernisien, Russell Howard, David Brechbiel, Hillary Dennison, Phillip Hess, Stephen Koss, Mario Noya, Wayne Simon, Alena Thompson, Donald McMullin, Sophie Laut, Tonia Hunt, Larry Gardner, Andrew Lanagan, Robert Hagood, Bruce Hohl, Andrew Uhl, Linda Smith, Dallas Zurcher, Eloise Stump, Miles Newman, Tai Ragan, James Caron","doi":"10.1007/s11207-025-02506-z","DOIUrl":"10.1007/s11207-025-02506-z","url":null,"abstract":"<div><p>We present the design and pre-launch performance of the Narrow Field Imager (NFI), which is an instrument designed to provide the inner field of view of the NASA Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission. This paper provides details of the NFI instrument concept, design, and pre-flight performance to give the potential user of the data a better understanding of how the observations are collected and the sources that contribute to the signal. NFI will contribute significantly to the scientific success of the PUNCH mission. The paper discusses the NFI design concepts, which include the optics, mechanical, and thermal. The performance measurements of the various instrument parameters meet or exceed the requirements derived from the mission science objectives. NFI is poised to take its place as a vital contributor to the science success of the PUNCH mission.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-025-02506-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145168536","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}
Solar PhysicsPub Date : 2025-07-22DOI: 10.1007/s11207-025-02503-2
Sean G. Sellers, Juie Shetye, Damian J. Christian, David B. Jess, Peter H. Keys, Gordon A. MacDonald, R. T. James McAteer, Jason Jackiewicz, Colin Hancock, Michael S. Thompson, Jamey E. Eriksen, Sara Jeffreys
{"title":"The Sunspot Solar Observatory Data Archive: Continuing Operations at the Dunn Solar Telescope","authors":"Sean G. Sellers, Juie Shetye, Damian J. Christian, David B. Jess, Peter H. Keys, Gordon A. MacDonald, R. T. James McAteer, Jason Jackiewicz, Colin Hancock, Michael S. Thompson, Jamey E. Eriksen, Sara Jeffreys","doi":"10.1007/s11207-025-02503-2","DOIUrl":"10.1007/s11207-025-02503-2","url":null,"abstract":"<div><p>The Sunspot Solar Observatory Data Archive (SSODA) stores data acquired with the suite of instruments at the Richard B. Dunn Solar Telescope (DST) from February 2018 to the present. The instrumentation at the DST continues to provide high cadence imaging, spectroscopy, and polarimetry of the solar photosphere and chromosphere across a wavelength range from 3500 Å to 11,000 Å. At the time of writing, the archive contains approximately 374 TiB of data across more than 520 observing days (starting on February 1, 2018). These numbers are approximate as the DST remains operational, and is actively adding new data to the archive. The SSODA includes both raw and calibrated data. A subset of the archive contains the results of photospheric and chromospheric spectropolarimetric inversions using the Hazel-2.0 code to obtain maps of magnetic fields, temperatures, and velocity flows. The SSODA represents a unique resource for the investigation of plasma processes throughout the solar atmosphere, the origin of space weather events, and the properties of active regions throughout the rise of Solar Cycle 25.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12283800/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144706027","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}
Solar PhysicsPub Date : 2025-07-18DOI: 10.1007/s11207-025-02482-4
Arik Posner, Ian G. Richardson, Cary J. Zeitlin
{"title":"Mars Ground Level Enhancements in the Context of the Solar Energetic Particle Clock","authors":"Arik Posner, Ian G. Richardson, Cary J. Zeitlin","doi":"10.1007/s11207-025-02482-4","DOIUrl":"10.1007/s11207-025-02482-4","url":null,"abstract":"<div><p>In this work we discuss the growing ensemble of solar energetic particle events registered on the Martian surface, including their temporal appearance and solar sources. Solar energetic particle events have been observed from the surface of Mars since soon after the August 2012 landing of the Radiation Assessment Detector onboard Curiosity. The Martian atmosphere prevents protons and heavy ions below 140 – 190 MeV/n kinetic energy from directly reaching the Martian surface. This cut-off is high enough to limit the number of solar energetic particle events measured on the surface to only 19 in ∼ 12 1/2 years. Yet we find in this analysis that proton acceleration that gives rise to Mars ground level enhancements takes place predominantly at or near the solar eruption site, while transport to Mars incurs a delay in onset, and, as we show here, peak intensity. These delays are a function of the longitudinal magnetic connection distance, defined here as the angular distance between the foot point of solar wind magnetic field lines that intersect the Mars environment and the source longitude of the solar magnetic eruption. A distinct clustering of solar source locations at or near the Mars foot points at the Sun’s western limb relative to Mars is apparent, indicating lower flux thresholds from such preferred locations. We have developed a simple peak flux prediction tool for the Martian surface that could be used to reduce radiation exposure during future human exploration missions.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11207-025-02482-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145167369","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}
Solar PhysicsPub Date : 2025-07-18DOI: 10.1007/s11207-025-02515-y
Qi Li, Gui-Ming Le
{"title":"Heliolatitudinal Distribution and Hemispheric Asymmetry of Source Locations for Super Geomagnetic Storms (Dst ≤−250 nT) During Different Phases of Solar Cycles","authors":"Qi Li, Gui-Ming Le","doi":"10.1007/s11207-025-02515-y","DOIUrl":"10.1007/s11207-025-02515-y","url":null,"abstract":"<div><p>We studied the heliolatitudinal distribution and hemispheric asymmetry of source locations for super geomagnetic storms (SGSs) (Dst <span>(leq -250)</span> nT) during the ascending phase, solar maximum, descending phase, and solar minimum. The proportions of SGSs during the ascending phase, solar maximum, descending phase, and solar minimum were 16.1%, 33.9%, 48.2% and 1.8%, respectively. For SGSs with source locations in the heliolatitude above 20° in both hemispheres, the proportions during the ascending phase, solar maximum, descending phase, and solar minimum were 50%, 26.3%, 31.2%, and 0%, respectively. For SGSs with source locations within the heliolatitude range of [11°, 20°] in both hemispheres, the proportions during these phases were 50%, 52.6%, 43.8%, and 100%, respectively. For SGSs with source locations within the heliolatitude range of [0°, 10°] in both hemispheres, the proportions during these phases were 0%, 21.1%, 25%, and 0%, respectively. For all SGSs, the N–S asymmetry was significant over the period from 1932 to 2024. Specifically, during the ascending phase, solar maximum, and descending phase, the N–S asymmetries were significant, marginally significant, and not significant, respectively. Throughout these periods, the source locations of the SGSs were consistently dominated by the northern hemisphere. For all SGSs, the E–W asymmetry was insignificant over the period from 1932 to 2024. Specifically, during the ascending phase, the E–W asymmetry remained insignificant. In contrast, during the solar maximum, the E–W asymmetry became significant, with SGS source locations predominantly in the western hemisphere and an anti-correlation observed between the number of SGSs in the two hemispheres. During the descending phase, the E–W asymmetry was significant once again, but this time with SGS source locations dominated in the eastern hemisphere, maintaining the anti-correlation between the two hemispheres. Only one SGS was observed during the solar minimum, with a source location at S11W21.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145167368","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}
Solar PhysicsPub Date : 2025-07-17DOI: 10.1007/s11207-025-02510-3
Aman Kumar, Vipin Kumar
{"title":"Hybrid-Ensemble Deep-Learning Models to Enhance the Sunspot Prediction and Forecasting of Solar Cycle 26","authors":"Aman Kumar, Vipin Kumar","doi":"10.1007/s11207-025-02510-3","DOIUrl":"10.1007/s11207-025-02510-3","url":null,"abstract":"<div><p>This study comprehensively evaluates deep-learning models across three types of sunspot data: 13-month smoothed Sunspot Number (SSN), yearly SSN, and mean monthly SSN data. Traditional models such as LSTM, GRU, CNN, RNN, and BiLSTM are compared against proposed hybrid models: Hybrid1 (CNN-DilatedLSTM-BiLSTM-GRU), Hybrid2 (CNN-GRU-RNN with Dropout Regularization), Hybrid3 (CNN-GRU), Hybrid4 (CNN-GRU-RNN without Dropout) (Hybrid2 and Hybrid4 both integrate CNN-GRU-RNN architectures, but Hybrid2 introduces Dropout layers to reduce overfitting, making it a regularized version of Hybrid4), and a Hybrid Ensemble model (Hybrid2 + Hybrid4). Key metrics like RMSE, MAE, MSE, and R<sup>2</sup> are used to assess model performance. The results indicate that hybrid models consistently outperform traditional models across all datasets. Specifically, the Hybrid Ensemble achieves enhanced predictive accuracy, recording an RMSE of 4.062 and R<sup>2</sup> of 0.9964 for 13-month smoothed SSN data, an RMSE of 22.11 and R<sup>2</sup> of 0.8920 for yearly SSN data, and an RMSE of 24.61 and R<sup>2</sup> of 0.8826 for mean monthly SSN data. These findings demonstrate the ability of hybrid models, especially the Hybrid Ensemble, to effectively capture complex patterns in sunspot time-series data.</p><p>In addition to model evaluation, this study provides forecasted SSN values for Solar Cycle 26, projecting a gradual increase in solar activity from 2025 (SSN: 112.39) to a peak in 2036 (SSN: 165.35), followed by a slight decline in 2037 (SSN: 155.25), with the lowest SSN occurring in 2032 (SSN: 10.41). These forecasts align well with known solar cycle variations and offer valuable insights into upcoming solar activity and its implications for space weather, climate, and technology. A Friedman non-parametric test was conducted to rank model performance, confirming the Hybrid Ensemble as the top performer. Holm-adjusted multiple comparisons showed negligible differences, reinforcing the robustness of the hybrid and ensemble approaches. This research highlights the value of combining different architectures to improve forecasting accuracy, especially for complex scientific time-series data such as solar activity.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 7","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145143788","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":"Counter-Streaming Velocities in a Quiescent Filament","authors":"Garima Karki, Brigitte Schmieder, Pascal Démoulin, Pooja Devi, Ramesh Chandra, Reetika Joshi","doi":"10.1007/s11207-025-02509-w","DOIUrl":"10.1007/s11207-025-02509-w","url":null,"abstract":"<div><p>Filaments/prominences are cold plasma (<span>(approx 10^{4})</span> K) embedded in the solar corona, two orders of magnitude hotter. Filament plasma is structured by the magnetic field in thin elongated threads. Counter-streaming flows have been observed. The aim of this paper is to characterize these flows. For that, we use high spatial resolution observations of spectral data obtained with THEMIS in H<span>(alpha )</span> and with IRIS in Mg II k lines on 29 September 2023. We best detect counter-streaming flows in both the blue and red wings of these spectral lines. They are forming long Doppler shifted strands slightly inclined on the filament axis. The blue/red shift alternates across the strands at the arc second scale. H<span>(alpha )</span> spectral profiles with large widths are interpreted as formed by multi-strands with opposite velocity directions. The absorption in the core of Mg II k line is also broader than in the chromosphere. This corresponds also to counter-streaming velocities. We derive that a fraction of the filament plasma is moving at supersonic speed (of the order of 20 km s<sup>−1</sup>) with the assumption that the filament is optically thick. We conclude that the counter-directed Doppler shifts might not be magnetic field aligned flows but rather correspond to kink transverse oscillations of the magnetic field with independent motions in nearby strands.</p></div>","PeriodicalId":777,"journal":{"name":"Solar Physics","volume":"300 7","pages":""},"PeriodicalIF":2.4,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145143742","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}