Researchers use NVST high-resolution data to study chromospheric fibrils around quiescent filament

Using high-resolution data from the New One-meter Vacuum Solar Telescope (NVST), a research team led by Professor Yan Xiaoli from the Yunnan Observatories of the Chinese Academy of Sciences (CAS) conducted a comprehensive study on the physical properties and oscillations of chromospheric fibrils surrounding a quiescent filament.

The study was published in Monthly Notices of the Royal Astronomical Society.

Focusing on a resting filament observed by the NVST on November 1, 2023, the team analyzed 63 surrounding chromospheric fibrils.

By combining high-resolution Hα data from NVST with extreme ultraviolet (EUV) data and line-of-sight magnetograms from the Solar Dynamics Observatory, as well as full-disk images from China’s Hα Solar Explorer, the team found that although the orientations of the fibrils differed significantly on each 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 to 650 seconds, widths of 0.32 to 0.85 megameters (Mm), maximum lengths of 3 to 8.5 Mm, projection velocities of 7 to 29 km·s.^-1and decelerations from 45 to 474 m s^-2.

To study the oscillatory properties of the fibrils, the team enhanced weak signals using a motion magnification algorithm. This technique identified transverse oscillations in some fibrils, with periods of 269 to 289 seconds and phase velocities of 13.7 to 25.8 km·s.^-1characteristics consistent with magnetohydrodynamic torsion waves.

Power spectrum analysis showed that the dominant oscillation periods were concentrated in the range of 4.8 to 6.6 minutes (288 to 396 seconds), corresponding to a frequency range of 2.5 to 3.5 MHz. Additionally, the oscillation power was significantly higher in the fibril regions than in the surrounding areas, peaking at the fibril roots.

Energy estimates indicate that the energy flow carried by these waves ranges from 0.4 to 6.5 W·m^-2which is insufficient to support only the chromospheric radiative loss.

The study supports the theory that the fibrils are driven by magnetoacoustic shocks, providing new insights into energy transport in the solar chromosphere. It also highlights the ability of the high spatio-temporal resolution of the NVST to observe fine chromospheric structures.