  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 (Seki et al. 2017), we analysed the Doppler
velocity of an H{\alpha} filament and found that the standard deviation of the
line-of-sight-velocity (LOSV) 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 03:40UT on 2016 November 5 in the vicinity of
NOAA AR 12605. It includes a coronal line observation and the extrapolation of
the surrounding magnetic fields. We found that both the spatially averaged
micro-turbulence inside the filament and the nearby coronal line emission
increased 6 and 10 hours 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.
