Using high-resolution data from the 1-meter New Vacuum Solar Telescope (NVST), PhD student DONG Qifan, supervisor Prof. YAN Xiaoli and other colleagues from the Fuxian Lake Solar Observatory of the Yunnan Observatories (Chinese Academy of Sciences) have conducted a detailed study on the physical properties and oscillations of chromospheric fibrils surrounding a quiescent filament. The findings have been published in Monthly Notices of the Royal Astronomical Society.
Focusing on a quiescent filament observed by the NVST on November 1, 2023, the team analyzed 63 surrounding chromospheric fibrils. By combining high-resolution Hα data from the NVST with Extreme Ultraviolet data and line-of-sight magnetograms from the Solar Dynamics Observatory, as well as full-disk images from the Chinese Hα Solar Explorer, the team discovered that while the fibrils’ orientations differed significantly on either side of the filament, their other physical properties were similar.
The analysis revealed that the fibrils exhibited a range of physical properties, including lifetimes of 150-650 s, widths of 0.32-0.85 Mm, maximum lengths of 3-8.5 Mm, projection velocities of 7-29 km·s⁻¹, and decelerations of 45-474 m·s⁻².
To investigate oscillatory properties, the team enhanced the faint signals using a motion magnification algorithm. This technique identified transverse oscillations in some fibrils, with periods of 269-289 s and phase speeds of 13.7-25.8 km·s⁻¹, characteristics consistent with magnetohydrodynamic kink waves.
Power spectrum analysis showed that the dominant oscillation periods were concentrated in the range of 4.8-6.6 minutes (288-396 seconds), corresponding to a frequency range of 2.5-3.5 mHz. Furthermore, the oscillation power was significantly higher in the fibril regions than in the surrounding regions, peaking at the fibril roots.
Energy estimates indicate that the energy flux carried by these waves ranges from 0.4 to 6.5 W·m⁻², which is insufficient to solely sustain the chromospheric radiative loss.
The research provides compelling evidence supporting the theory that fibrils are driven by magnetoacoustic shocks, offering new observational insights into energy transport in the solar chromosphere. The work also highlights the capability of the NVST's high spatiotemporal resolution for observing fine chromospheric structures and demonstrates the strength of China's multi-facility initiatives in advancing solar physics.
This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Science Fund for Distinguished Young Scholars, the General Program of the National Natural Science Foundation of China, the Yunnan Key Laboratory of Solar Physics and Space Science, and the Yunnan Fundamental Research Projects.
Figure 1. Panel (a): Motion-magnified view of the fibril. The white lines indicate the positions for analyzing transverse oscillations. Panel (b): The space-time plots corresponding to positions 1-8 in panel (a). Panel (c): The lines represent the fitted minimum intensity values for each column. Image by YAN.
Contact:
YAN Xiaoli
Yunnan Observatories, CAS
E-mail:yanxl@ynao.ac.cn
