Small-scale Turbulent Motion of the Plasma in a Solar Filament as the Precursor of Eruption

A filament, a dense cool plasma supported by the magnetic fields in the solar corona, often becomes unstable and erupts. It is empirically known that the filament often demonstrates some activations such as a turbulent motion prior to eruption. In our previous study, we analyzed the Doppler velocity of an Hα filament and found that the standard deviation of the line-of-sight velocity distribution in a filament, which indicates the increasing amplitude of the small-scale motions, increased prior to the onset of the eruption. Here, we present a further analysis on this filament eruption, which initiated approximately at 03:40 UT on 2016 November 5 in the vicinity of NOAA Active Region 12605. It includes a coronal line observation and the extrapolation of the surrounding magnetic fields. We found that both the spatially averaged microturbulence inside the filament and the nearby coronal line emission increased 6 and 10 hr prior to eruption, respectively. In this event, we did not find any significant changes in the global potential field configuration preceding the eruption for the past 2 days, which indicates that there is a case in which it is difficult to predict the eruption only by tracking the extrapolated global magnetic fields. In terms of space weather prediction, our result on the turbulent motions in a filament could be used as the useful precursor of a filament eruption.