arXiv subjects

Feiyang Sha

Publications and source records attributed to Feiyang Sha.

7 recordsLinked to original sources

arXiv2026

Statistical Study of Solar Prominence Plumes Based on NVST H$\alpha$ Observations

Plumes are one of the most representative dynamic features observed in prominences and play a key role in mass and magnetic transport within them. However, their physical nature and triggering processes remain actively debated. Based on limb H$\alpha$ observations from the New Vacuum Solar Telescope (NVST) during 2013--2025, we statistically investigated 34 plumes with clear and complete evolutions by developing an automated image-processing pipeline. It is revealed that plume lifetimes mainly range from 300 s to 700 s, with vertical displacements between 3--7 Mm. The mean widths and velocities are concentrated in the range of 0.5--1.5 Mm and 10--20 km s$^{-1}$, respectively. Besides wide distribution ranges, plume parameters exhibit irregular evolution fluctuations, indicating that the formation and evolution of various plumes may exhibit different physical patterns. Correlation analysis among the parameters further reveals that: (1) Positive correlations were found among lifetime, vertical displacement, and mean width, indicating an intrinsic coupling between the temporal and spatial scales of plumes. (2) Trajectory curvature is negatively correlated with lifetime, vertical displacement, and velocity. Accelerating and width-contracting plumes typically have lower curvature, suggesting that curvature may reflect environmental influences and the stability of plumes. (3) Plumes with higher initial velocities were more likely to be accompanied by precursor brightening, suggesting that these plumes may be triggered by magnetic reconnection. Furthermore, we infer that some plumes in non-bubble regions may be inherently driven by mini-filament eruptions. These results establish a statistical framework for prominence plumes and reveal diversity in their dynamical evolution and triggering mechanisms.

astro-ph.SR↗

arXiv2026

Observational Technological Innovations and Future Development of the Lijiang Coronagraph

As a core ground-based coronal observation facility in China's low-latitude high-altitude regions, the Lijiang Coronagraph leverages the natural advantages of Lijiang Astronomical Observation Station, including its 3200 m altitude and low atmospheric turbulence. It has undergone a full development process, from introduction via Chinese-Japanese cooperation to independent innovation and iteration. This paper systematically summarizes its core technological innovations: upgrade of the automatic operating system, integration of the dual-band observation system, stray light suppression based on image differencing before and after cleaning, and high-precision image calibration and registration. These advances have significantly improved observation efficiency and data quality, laying a solid foundation for high-quality observations. Scientifically, the data reveal that 1.1 solar radii is a highly correlated region between coronal green line brightness and magnetic field intensity. The study also confirms a strong correlation between the coronal green line and the SDO/AIA 21.1 nm extreme ultraviolet band (correlation coefficient: 0.89-0.99), supporting early warning research on Coronal Mass Ejections (CMEs). These results provide key data for verifying coronal heating mechanisms and exploring the origin of the slow solar wind. The experience from the Lijiang Coronagraph not only lays a foundation for China's next-generation large-aperture coronagraphs, but also accelerates progress in low coronal observation capabilities, enabling the country to build internationally competitive capabilities in this field. The system is also an important part of the global coronal observation network.

astro-ph.SR↗

arXiv2026

Forward Modeling of Dust-Induced Stray Light in Ground-Based Coronagraphs: A Dual-Path Monitoring Approach for High-Precision Inner Corona Observations

High-precision ground-based observations of the inner corona (1.05-2.0 R_sun) are fundamentally constrained by instrumental stray light, particularly the additive background from dynamic dust accumulation on the objective lens. To address this issue, we propose a correction method for the Spectral Imaging Coronagraph (SICG) based on dual-path real-time monitoring and forward physical modeling. By simultaneously imaging the objective lens surface, we obtain deterministic prior information on dust distribution. We construct a physical point-spread function using optical defocus parameters and reconstruct the nonuniform scattering background via convolution. Model parameters are retrieved through data-driven inversion constrained by polar coronal holes. The method demonstrates excellent robustness under varying contamination conditions. After correction, the rms noise in the polar background is reduced by approximately 67% on average, and the signal-to-background ratio improves by a factor of up to 3.7 under heavy contamination conditions. Comparisons with space-based Solar Dynamics Observatory/Atmospheric Imaging Assembly observations indicate that the corrected images recover the morphological structures of streamers with high fidelity. Further radial intensity analysis reveals that the correction process successfully restores the hydrostatic exponential decay characteristic of inner coronal radiation. The fitted decay coefficient corresponds to a plasma temperature of approximately 2.0 MK, consistent with the characteristic formation temperature of the Fe XIV 530.3 nm line. These results demonstrate that the method effectively eliminates the dominant systematic bias in ground-based observations, providing a reliable data foundation for high-precision coronal thermodynamic and dynamic research with the SICG.

astro-ph.SR↗

arXiv2025

Two-stage primary acceleration in filament initial eruption under a fan-spine magnetic configuration

Understaning the filament rising process is crucial for unveiling the triggering mechanisms of the coronal mass ejections and forecasting the space weather. In this paper, we present a detailed study on the filament initial eruption under a fan-spine structure. It was found that the filament underwent two distinct acceleration stages corresponding to a calss M1.0 and M4.6 flare event, respectively. The first acceleration stage commenced with the filament splitting, after which the upper portion was subsequently heated being a hot channel and slow rose at an average speed of 22 km/s. A set of hot reverse C-shaped loops appeared repeatedly during the filament splitting and a hook structure was recognized at this phase, suggesting ongoing growth of the magnetic flux rope (MFR). When it reached a certain altitude, the hot channel appeared to get into a quasi-static phase with its upper edge seriously decelerated and lower edge expanding downward. Approximately 30 minutes later, as a distinct annular ribbon appeared outside the hook structure, the hot channel rose again at a velocity over 50 km/s accompanied with rapid footpoints drifting, and experienced the second acceleration stage with its axial flux increased to 1.1 X 10^{21} Mx. It is deduced that the filament initial eruption under a magnetic dome possess multi kinetic process. We suggest that the magnetic reconnection taken place within and beneath the filament continues to trigger the growth of pre-eruptive MFR and the first acceleration, when the magnetic reconnection above the filament plays a key role in the second acceleration.

astro-ph.SR↗

arXiv2025

Mapping ground-based coronagraphic images to Helioprojective-Cartesian coordinate system by image registration

A few ground-based solar coronagraphs have been installed in western China for observing the low-layer corona in recent years. However, determining the Helioprojective Coordinates for the coronagraphic data with high precision is an important but challenging step for further research with other multi-wavelength data. In this paper, we propose an automatic coronal image registration method that combines local statistical correlation and feature point matching to achieve accurate registration between ground-based coronal green-line images and space-based 211 {\AA} images. Then, the accurate field of view information of the coronal green-line images can be derived, allowing the images to be mapped to the Helioprojective Cartesian Coordinates with an accuracy of no less than 0.1''. This method has been extensively validated using 100 days of coronal data spanning an 11-year period, demonstrating its broad applicability to ground-based coronagraphs equipped with green-line observations. It significantly enhances the scientific value of ground-based coronal data, enabling comprehensive studies of coronal transient activities and facilitating the joint analysis of data from multiple instruments. Additionally, it holds potential for future applications in improving the pointing accuracy of coronagraphs.

astro-ph.SR↗

arXiv2024

Investigating the Behavior and Spatiotemporal Variations of Green Line Emission in the Solar Corona

Understanding coronal structure and dynamics can be facilitated by analyzing green-line emission, which enables the investigation of diverse coronal structures such as coronal loops, streamers, coronal holes, and various eruptions in the solar atmosphere. In this study, we investigated the spatiotemporal behaviors of green-line emissions in both low and high latitudes across nine solar cycles, ranging from cycle 17 to the current cycle 25, using the Modified Homogeneous Data Set (MHDS). We employed methodologies such as cross-correlation, power spectral density (PSD), and wavelet transform techniques for this analysis. We found distinct behaviors in green line energy across various latitudinal distributions in the solar atmosphere. The trends observed at higher latitudes differ from those at lower latitudes. The emission behaviors show a close association with other solar phenomena like solar flares, sunspots, and coronal mass ejections (CMEs) throughout the solar cycles. The observed variations exhibit harmonic periods. The emission activity is significantly higher in the low latitudes, accounting for over 70 percent of the emissions, while the higher latitudes contribute less than 30 percent. The emissions exhibit asymmetric behavior between the northern and southern hemispheres, leading to a 44-year cycle of solar hemispheric dominance shifts. Various factors, such as Alfv\'en waves, solar magnetic fields, sunspots, differential rotation, and reconnection events, influence the observed differences in behavior between lower and higher latitudes, suggesting the existence of potential underlying phenomena contributing to deviations in properties, intensity, temporal dynamics, and spatiotemporal lifetime.

astro-ph.SR↗

arXiv2023

Characterization and Correction of the Scattering Background Produced by Dust on the Objective Lens of the Lijiang 10-cm Coronagraph

Scattered light from the objective lens, directly exposed to the intense sunlight, is a dominant source of stray light in internally occulted coronagraphs. The variable stray light, such as the scatter from dust on the objective lens, can produce varying scattering backgrounds in coronal images, significantly impacting image quality and data analysis. Using data acquired by the Lijiang 10-cm Coronagraph, the quantitative relationship between the distribution of dust on the objective lens and the resulting scattering backgrounds background is analyzed. Two empirical models for the scattering background are derived, and used to correct the raw coronal data. The second model, which depends on three parameters and performs better, shows that the scattering-background distribution varies with angle, weakens with increasing height, and enhances with increasing dust level on the objective lens. Moreover, we find that the dust on the center of the objective lens can contribute more significantly to the scattering background than on the edge. This study not only quantitatively confirms the significant impact of the stray light produced by dust on the objective lens of the coronagraph, but also corrects the coronal data with this stray light for the first time. Correcting for dust-scattered light is crucial for the high-precision calibration of ground-based coronagraph data, enabling a more accurate analysis of coronal structures. Furthermore, our model is envisioned to support the provision of reliable observational data for future routine coronal magnetic-field measurements using ground-based coronagraphs.

astro-ph.IM↗