  In this paper, we report the multiwavelength observations of the partial
filament eruption associated with a C1.2 class flare in NOAA active region
11236 on 13 June 2011. The event occurred at the eastern limb in the field of
view (FOV) of Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics
Observatory (SDO) spacecraft and was close to the disk center in the FOV of
Extreme-UltraViolet Imager (EUVI) on board the behind Solar Terrestrial
Relations Observatory (STEREO) spacecraft. During eruption, the filament splits
into two parts: the major part and runaway part. The major part flows along
closed loops and experiences bifurcation at the loop top. Some of the materials
move forward and reach the remote footpoint, while others return back to the
original footpoint. The runaway part flows along open field lines, which is
evidenced by a flare-related type III radio burst. The runaway part also
undergoes bifurcation. The upper branch of escapes the corona and evolves into
a jet-like narrow coronal mass ejection (CME) at a speed of 324 km s-1, while
the lower branch falls back to the solar surface. A schematic cartoon is
proposed to explain the event and provides a new mechanism of partial filament
eruptions
