  We present stereoscopic observations of six sequent eruptions of a filament
in the active region NOAA 11045 on 2010 Feb 8, with the advantage of the STEREO
twin viewpoints in combination with the earth viewpoint from SOHO instruments
and ground-based telescopes. The last one of the six eruptions is with a
coronal mass ejection, while the others are not. The flare in this successful
one is more intensive than in the others. Moreover, the filament material
velocity of the successful one is also the largest among them. Interestingly,
all the filament velocities are found proportional to their flare powers. We
calculate magnetic field intensity at low altitude, the decay indexes of the
external field above the filament, and the asymmetry properties of the
overlying fields before and after the failed eruptions and find little
difference between them, indicating the same coronal confinement for the failed
and the successful eruptions. The results suggest that, besides the confinement
of coronal magnetic field, the energy released in low corona should be another
crucial element for production of a failed or successful filament eruption.
That is, only a coronal mass ejection can be launched away if the energy
released exceeds some critical value, given the same coronal conditions.
