Solar Physics最新文献

Stellar eruptive prominences are one of the key components shaping stellar space weather environments. Moreover, due to the association of eruptive prominences with coronal mass ejections and their degrading influence on planetary atmospheres, they play a crucial role in the habitability of exoplanets.

In this article, we used the insights from solar extreme-ultraviolet (EUV) observations to develop and test a technique for the detection of stellar eruptive prominences. We focused on the EUV imaging observations of the entire Sun provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) in the 304 Å channel. For this proof-of-concept study, we selected only a few examples of solar eruptive prominences and minor solar flares and analysed them in the Sun-as-a-star mode that mimics the stellar EUV photospheric observations. To validate the results obtained from the SDO/AIA Sun-as-a-star analysis, we used the SDO/Extreme Ultraviolet Variability Experiment (EVE) irradiance measurements.

Our analysis showed markable intensity enhancements in the SDO/AIA 304 Å light curves during the prominence eruptions, with intensity increasing gradually for tens of minutes to several hours with enhancements of up to 1.5%. Flares exhibited a significantly faster intensity increase phase (a few minutes long) leading to large enhancements in the 304 Å channel of up to 8%. The large difference in the duration of the 304 Å intensity rise phases suggests that EUV stellar photometry in the He ii 304 Å line can provide signatures clearly attributable to stellar prominence eruptions or flares. However, development of robust techniques for detection of stellar eruptive prominences using the insights from EUV solar observations will require significantly broader statistical analyses that are beyond the scope of this work.

Reconstructing fine-scale magnetic structure from legacy SOHO/MDI magnetograms is essential for extending reliable photospheric diagnostics to periods predating SDO/HMI. We introduce Resolution Enhancement of Solar Magnetogram (RESM), a novel deep-learning framework designed to enhance MDI magnetograms by integrating Feature Enhancement Blocks (FEB) with a Convolutional Block Attention Module (CBAM) to recover compact magnetic concentrations and polarity-inversion structure selectively. RESM achieves strong agreement with HMI, yielding PSNR of 55.6 dB, SSIM of 0.948, PCC of 0.929, and RMSE (G) of 0.071 G compared to state-of-the-art techniques. Physics-aware assessment further shows that RESM preserves multiscale spectral power, maintains signed and unsigned flux budgets, and reproduces coherent PIL contours with high spatial fidelity. A case study of NOAA AR 11131 confirms improved recovery of compact flux bundles and refined PIL topology relative to MDI, enhancing the interpretability of archived observations for active-region characterisation and pre-eruption analysis. These results demonstrate that RESM provides reliable, physically consistent reconstructions of historical magnetograms, expanding their scientific utility.

The successive type-II solar radio bursts observed on 31 July 2012 by the Bruny Island Radio Spectrometer (BIRS) in the frequency range between 62 – 6 MHz is reported and analyzed. The first type-II radio burst shows clear fundamental and harmonic band structures, while only one band is observed for the second type-II radio burst and is considered as the harmonic band. The first type-II radio burst is observed in the frequency range of 57 – 27 MHz between 00:03 – 00:09 UT at the harmonic band. The second type-II burst is observed between 00:18 – 00:27 UT in the frequency range of 43 – 17 MHz. The type-II radio bursts are associated with a C6 class flare located at the south–eastern limb (S24E87) and a CME observed from STEREO and LASCO observations. The EUVI signatures of the CME are observed in the ST–B EUVI FOV between 23:56 (on 30 July 2012) to 00:06 UT (on 31 July 2012), and in the ST-B COR1 FOV between 00:10 – 00:35 UT moving within an average speed of 725 ± 101 km s⁻¹. The CME is observed in the LASCO C2 FOV after 00:12 UT as a partial halo CME moving with an average speed of 486 km s⁻¹. The height-time plot shows that the first type-II radio burst was formed by the CME-shock along the shock front and the second type-II radio burst along the shock-dip structure, probably the dip structure results from the shock transiting across the high dense streamer structure. The successive type-II bursts are most likely produced by the single CME shock and their interactions with the streamer structures. The first type-II radio burst by the CME shock and the second type-II radio burst by the CME shock–streamer interactions.

The complex nature of sunspots presents a constant challenge in understanding their dynamics and how they interact with their surrounding environment. A new method to analyse sunspot rotations has been presented, by which the rotation of sunspots can be tracked using multiple ellipses fitted throughout the sunspot umbrae. The method is applied to sunspots in active regions of differing degrees of flaring, to determine a correlation between the rotation of the sunspot and the appearance of a flare. The study reveals that sunspots in active regions associated with flares present complex patterns of rotation within the umbral plasma, where multiple regions of rotation can be observed. Further implications of this study could help determine the link between sunspots and flares, which will contribute towards the betterment of flare forecasting.

Coronal holes (CHs) are the darkest regions observed on the Sun, serving as key sources of open magnetic fields and fast solar-wind streams. Accurate and consistent delineation of their boundaries is crucial for analyzing their physical properties, understanding solar dynamics, and ultimately improving space weather forecasts. However, developing precise and automated methods for their detection and tracking across extensive observational datasets remains a significant challenge. To address this, we developed the DEtection and Tracking Algorithm for Coronal Holes (DETACH), leveraging advanced machine-learning techniques. DETACH was specifically developed and rigorously validated using extreme ultraviolet (EUV) 193 Å wavelength images from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument. This novel algorithm significantly advances prior CH detection models, notably minimizing the erroneous identification of solar filaments as CHs and achieving superior accuracy across a comprehensive suite of evaluation metrics. Additionally, another key innovation of DETACH is its robust and precise CH tracking functionality across different observational times, a crucial capability largely absent in previous methodologies. DETACH offers a state-of-the-art, high-performance solution for accurate coronal hole identification and tracking, providing invaluable data and a powerful tool to enhance our understanding of solar activity and advance space-weather prediction capabilities.

The Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission is a NASA Small Explorer to determine the cross-scale processes that unify the solar corona and heliosphere. PUNCH has two science objectives: (1) understand how coronal structures become the ambient solar wind, and (2) understand the dynamic evolution of transient structures, such as coronal mass ejections, in the young solar wind. To address these objectives, PUNCH uses a constellation of four small spacecraft in Sun-synchronous low Earth orbit, to collect linearly polarized images of the K corona and young solar wind. The four spacecraft each carry one visible-light imager in a 1 + 3 configuration: a single Narrow Field Imager solar coronagraph captures images of the outer corona at all position angles, and at solar elongations from 1.5° (6 R_⊙) to 8° (32 R_⊙); and three separate Wide Field Imager heliospheric imagers together capture views of the entire inner solar system, at solar elongations from 3° (12 R_⊙) to 45° (180 R_⊙) from the Sun. PUNCH images include linear-polarization data, to enable inferring the three-dimensional structure of visible features without stereoscopy. The instruments are matched in wavelength passband, support overlapping instantaneous fields of view, and are operated synchronously, to act as a single “virtual instrument” with a 90^∘ wide field of view, centered on the Sun. PUNCH launched in March of 2025 and began science operations in June of 2025. PUNCH has an open data policy with no proprietary period, and PUNCH Science Team Meetings are open to all.

Using a recently suggested magneto-morphological classification (MMC, Abramenko (2021)) of solar active regions (ARs), we explored 3048 ARs, observed from 12 May 1996 to 27 December 2021. Magnetograms were acquired with the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) and with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). ARs were separated between three classes: class A - regular ARs (bipoles which follow the empirical rules compatible with the mean field dynamo theory); class B - irregular ARs (“wrong” bipoles and multipolars); class U - unipolar sunspots. An aim of the present study is to explore time variations of a typical unsigned magnetic flux of ARs of different classes. The typical flux was acquired as the mean flux over all ARs of a given class observed during one solar rotation. The time profiles of the mean fluxes for different classes were compared. We found that, except for periods of deep solar minima, the mean flux of B-class ARs always dominates that of A-class ARs, and, what is the most important, the time profile of B-class ARs is highly intermittent versus the rather smooth and quazi-constant A-class profile. Intermittency implies a direct involvement of turbulence. We conclude that, through the entire active phase, the Sun is capable of producing regular moderate ARs at a quazi-constant rate along with the production of large and complex irregular ARs in the very intermittent manner. The result is the first observational evidence for the long-standing speculative assumption on the involvement of the convection zone turbulence into the regular global dynamo-process on a stage of the active regions formation.

Recent spectroscopic analyses of observations from the EUV Variability Experiment (EVE) appear to show the presence of hot high-speed prograde flows in the solar atmosphere associated with solar active regions. However, the existence of these flows has not yet been confirmed in observations from other instruments or at other wavelengths. In this work we attempt to determine whether similar prograde flows can also be detected in soft X-ray spectroscopic data. To examine this, we analyze soft X-ray spectroscopic data from the Yohkoh Bragg Crystal Spectrometer (BCS). Since BCS was a whole-Sun instrument, in order to ensure clear spectroscopic results from a single active region, we restrict consideration to intervals when only a single active region moved across the Sun from limb to limb. We found three suitable intervals. Our analysis of the data for these intervals do not indicate the presence of prograde flows in soft X-rays, and we establish an upper limit of about 30 km s⁻¹ for such a pattern. Three possibilities may account for this difference with the EVE observations: (a) the hot prograde flows may not exist, and the EVE result is an artifact; (b) the hot prograde flows may not occur at the higher temperatures observed by soft X-rays; (c) Yohkoh BCS may only have been capable of observing flare emissions and lacked the sensitivity necessary to detect quiescent active regions, suggesting that the physics of flaring loops may differ from that of slowly-varying active-region loops. We favor explanation (a) but have not identified the exact nature of the artifact.

The Citizen CATE 2024 next-generation experiment placed 43 identical telescope and camera setups along the path of totality during the total solar eclipse (TSE) on 8 April 2024 to capture a 60-minute movie of the inner and middle solar corona in polarized visible light. The 2024 TSE path covered a large geographic swath of North America and we recruited and trained 36 teams of community participants (“citizen scientists”) representative of the various communities along the path of totality. Afterwards, these teams retained the equipment in their communities for on-going education and public engagement activities. Participants ranged from students (K12, undergraduate, and graduate), educators, and adult learners to amateur and professional astronomers. In addition to equipment for their communities, CATE 2024 teams received hands-on telescope training, educational and learning materials, and instruction on data analysis techniques. CATE 2024 used high-cadence, high-dynamic-range (HDR) polarimetric observations of the solar corona to characterize the physical processes that shape its heating, structure, and evolution at scales and sensitivities that cannot be studied outside of a TSE. Conventional eclipse observations do not span sufficient time to capture changing coronal topology, but the extended observation from CATE 2024 does. Analysis of the fully calibrated dataset will provide deeper insight and understanding into these critical physical processes. We present an overview of the CATE 2024 project, including how we engaged local communities along the path of totality, and the first look at CATE 2024 data products from the 2024 TSE.