Solar Physics最新文献

Solar filaments are well-known tracers of polarity inversion lines that separate two opposite magnetic polarities on the solar photosphere. Because observations of filaments began long before the systematic observations of solar magnetic fields, historical filament catalogs can facilitate the reconstruction of magnetic polarity maps at times when direct magnetic observations were not yet available. In practice, this reconstruction is often ambiguous and typically performed manually. We propose an automatic approach based on a machine-learning model that generates a variety of magnetic polarity maps consistent with filament observations. To evaluate the model and discuss the results, we use the catalog of solar filaments and polarity maps compiled by McIntosh. We realize that the process of manual compilation of polarity maps includes not only information on filaments, but also a large amount of prior information, which is difficult to formalize. To compensate for the lack of prior knowledge for the machine-learning model, we provide it with polarity information at several reference points. We demonstrate that this process, which can be considered as the user-guided reconstruction or superresolution, leads to polarity maps that are reasonably close to hand-drawn ones and additionally allows for uncertainty estimation.

Utilizing data from the Solar Magnetism and Activity Telescope (SMAT), analytical solutions of polarized radiative transfer equations, and in-orbit test data for the Full-disk Magnetograph (FMG) onboard the Advanced Space based Solar Observatory (ASO-S), this study reveals the magnetic-sensitivity spectral positions for the Fe i (lambda ) 5234.19 Å working line used by FMG. From the experimental data of SMAT, it is found that the most sensitive position is located at the line center for linear polarization (Stokes Q/U), while it is about −0.07 Å away from the line center for circular polarization (Stokes V). Moreover, both the theoretical analysis and the in-orbit test data analysis of FMG confirm the above results. Additionally, the theoretical analysis suggests the presence of distinct spectral pockets (centered at 0.08 – 0.15 Å) from the line, harboring intense magnetic sensitivity across all three Stokes parameters. Striking a balance between high sensitivity for both linear and circular polarization, while capturing additional valuable information, a spectral position of −0.08 Å emerges as the champion for routine FMG magnetic field observations.

The measurements of the Total Solar Irradiance (TSI) is a primary means to investigate solar activity and key measurement for understanding global climate change. The aperture diffraction is an error factor for the Solar Irradiance Absolute Radiometer (SIAR) on the Fengyun-3F (FY-3F) satellite. The diffraction effect correction factors can currently only be obtained by simulation, and they are obtained based on a series of approximate conditions that do not allow the accuracy of the diffraction correction results to be assessed. In this paper, we establish the diffraction effect measurement equipment based on the dark imaging technology and the theory of diffraction by Fraunhofer. The total light image and the aperture diffraction images of different angles were obtained by the CCD camera. The images were corrected by linearity, background, and continuity. Then, the diffraction effect curve of diffraction angle can be obtained. Finally, the diffraction correction factor of SIAR/FY-3F can be obtained by the accumulation of multiple apertures and combining the weighted integration of the solar spectrum. The results illustrated that the value of the diffraction correction factor of the SIAR aperture system on the FY-3F satellite is (2.85times 10^{-3}), and the uncertainty of diffraction effect experimental measurement is 4.62%, which reduces the measurement error of the diffraction effect on the total solar irradiance to (1.32times 10^{-4}). This result provides a technical basis for high-precision TSI measurement.

We compile the catalog of Hvar Observatory (HVAR) solar observations in the time period corresponding to regular digitally stored chromospheric and photospheric observations 2010 – 2019. We make basic characterization of observed phenomena and compare them to catalogs that are based on full-disk solar images. We compile a catalog of observed active regions (ARs) consisting of 1100 entries, where each AR is classified according to McIntosh and Mt Wilson classifications. We find that HVAR observations are biased towards more frequently observing more complex ARs and observing them in longer time periods, likely related to the small field of view not encompassing the whole solar disk. In H(alpha ) observations, we catalog conspicuous filaments/prominences and flares. We characterize filaments according to their location, chirality (if possible), and eruptive signatures. Analysis of the eruptive filaments reveals a slight bias in the HVAR catalog towards observation of partial eruptions, possibly related to the observers’ tendency to observe filaments that already showed some activity. In the flare catalog we focus on their observed eruptive signatures (loops or ribbons) and their shape. In addition, we associate them to GOES soft X-ray flares to determine their corresponding class. We find that HVAR observations seem biased towards more frequently observing stronger flares and observing them in longer time periods. We demonstrate the feasibility of the catalog on a case study of the flare detected on 2 August 2011 in HVAR H(alpha ) observations and related Sun-to-Earth phenomena. Through flare–CME–ICME association we demonstrate the agreement of remote and in situ properties. The data used for this study, as well as the catalog, are made publicly available.

Clouds in the sky can significantly affect full-disk observations of the Sun. In cloud-covered full-disk H(alpha ) images, certain solar features become obscured, posing challenges for further solar research. Obtaining both cloud-covered and corresponding cloud-free images is often challenging, resulting in poor alignment of image pairs in the dataset, which adversely affects the performance of cloud removal models. We use RPix2PixHD, a novel network designed to translate cloud-covered images into cloud-free ones while mitigating the effects of misaligned data on the model. RPix2PixHD comprises two main components, Pix2PixHD and RegNet. Pix2PixHD includes a multiresolution generator and a multiscale discriminator. The generator takes cloud-covered images as input to produce cloud-free images. RegNet computes a deformation field using the generated cloud-free images and the ground truth cloud-free images. This deformation field is then used to resample the generated cloud-free images, resulting in registered images. The correction loss is calculated based on these registered images and utilized for training the generator, thereby enhancing the model’s cloud removal effectiveness. We conducted cloud removal experiments on full-disk H(alpha ) images obtained from the Huairou Solar Observing Station (HSOS). The experimental results demonstrate that RPix2PixHD effectively removes clouds from cloud-covered solar H(alpha ) images, successfully restoring solar feature details and outperforming comparative methods.

Prominences are important features in the solar atmosphere. Their activities often develop into solar eruptions, such as flares and/or coronal mass ejections. We report here on observations of activities of two crossing prominences and the resulting oscillations observed with the Advanced Space-based Solar Observatory (ASO-S) and the Solar Dynamics Observatory. We observed the two crossing prominences rising simultaneously with a speed of about 100 km s⁻¹. The lower-lying prominence consists of threads that show increase of writhe during the rising process. We find evidence that the writhe of the lower-lying prominence is transferred into the overlying one. This transfer of writhe leads to a failure of the eruption of the lower-lying prominence and a shearing motion of the legs of the overlying prominence. The failed eruption of the lower-lying prominence also triggers kink oscillations of its threads, which show periods of about 300 s and amplitudes of less than 10 Mm. Such oscillations are considered to be intrinsic mode and can help to probe the magnetic field of the prominence. Our observations support the idea that the transfer and release of writhe play an important role in confining eruptions of a prominence, and interactions among prominences/filaments might be a crucial aspect of a solar eruption.

This paper presents a detailed study of the type II solar radio burst that occurred on 06 March 2014 using combined data analysis. It is a classical radio event consisting of type III radio burst and a following type II radio burst in the dynamic spectrum. The type II radio burst is observed between 235 – 130 MHz (120 – 60 MHz) in harmonic (fundamental) bands with the life time of 5 minutes between 09:26 – 09:31 UT. The estimated speed of type II burst by applying two-fold Saito model is ∼ 650 km s⁻¹. An extreme ultraviolet (EUV) wave is observed with Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The very close temporal onset association of the EUV wave and flare energy release indicates that the EUV wave is likely produced by a flare pressure pulse. The eruption is also accompanied by a weak coronal mass ejection (CME) observed with the coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) and the twin Solar Terrestrial Relations Observatory (STEREO). The plane of sky speed of the CME was ∼ 252 km s⁻¹ in the SOHO/LASCO-C2 and ∼ 280 km s⁻¹ in the STEREO-B/SECCHI-COR1 images. The EUV wave has two wave fronts, one expanding radially outward and the other one moving along the flare loop arcade. The source position of the type II burst imaged by the Nançay Radio Heliograph (NRH) shows that it was associated with the outward moving EUV wave. The CME is independent of the shock wave as confirmed by the location of NRH radio sources below the CME’s leading edge. Therefore the type II radio burst is probably ignited by the flare. This study shows the possibility of EUV wave and coronal shock triggered by flare pressure pulse, generating the observed type II radio burst.

The Ludendorff coronal flattening index is a quantitative parameter to analyze the global structure and shape of the corona. This index plays a crucial role in identifying solar magnetic activity and estimating the phase of the solar cycle. We observed a total solar eclipse on 20 April 2023 in Timor-Leste and obtained a Ludendorff coronal flattening index of (0.109pm 0.025) by analyzing isophotes in white-light coronal images. Based on the composite image of the corona, streamers and plumes were observed extending in various directions across the solar disk, indicating that the Sun was in the ascending phase of its cycle. To establish the relationship between the coronal flattening index and the solar cycle phase, historical total solar eclipse data (1893 – 2013) were analyzed, focusing on smoothed sunspot numbers and flattening indices during the ascending phase. Two datasets, designated as “full” and “conservative”, were constructed considering temporal constraints relative to solar maxima and minima. The coronal morphology observed during the 20 April 2023 total solar eclipse corresponded to a premaximum phase, with values of (0.673pm 0.172) and (0.613pm 0.171) for the full and conservative datasets, respectively. We also developed a multilinear correlation and polynomial regression of second order models to predict the peak amplitude of the current solar cycle using both datasets. The full dataset predicted a peak on 3 December 2024 with amplitudes of (173pm 23) and (163pm 21) for the respective models. Conversely, the conservative dataset predicted a peak on 30 May 2025 with amplitudes of (180pm 24) and (180pm 25) for the respective models. These findings suggest that Solar Cycle 25 will likely be stronger than Solar Cycle 24.