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Fine-scale structures and material flows of quiescent filaments observed by New Vacuum Solar Telescope

Study on the small-scale structures and material flows of solar quiescent filaments is very important for understanding the formation and equilibrium of solar filaments. Using the high resolution Hα data observed by the New Vacuum Solar Telescope (NVST), we present the structures of the barbs and the material flows along the threads across the spine in two quiescent filaments on 2013 September 29 and on 2012 November 2, respectively. During the evolution of the filament barb, several parallel tube-shaped structures formed and the width of the structures ranges from about 2.3 Mm to 3.3 Mm. The parallel tube-shaped structures merged together accompanied with the material flows from the spine to the barb. Moreover, the boundary between the barb and surrounding atmosphere is very neat. The counter-streaming flows were not found to appear alternately in the adjacent threads of the filament. However, the large-scale patchy counter-streaming flows are detected in the filament. The flows in one patch of the filament have the same direction and the flows in the adjacent patch have opposite directions. The patches of two opposite flows with a size of about ten arcseconds exhibited alternately along the spine of the filament. The velocity of these material flows ranges from 5.6 km/s to 15.0 km/s. The material flows along the threads of the filament did not change their direction for about two hours and fourteen minutes during the evolution of the filament. Our results confirm that the large-scale counter-streaming flows with the certain width along the threads of solar filaments exist and are well coaligned with the threads.