  On 2012 July 11, two solar filaments were observed in the northeast of the
solar disk and their eruptions due to the interaction between them are studied
by using the data from the Solar Dynamics Observatory (SDO), Solar TErrestrial
RElations Observatory (STEREO) and Global Oscillation Network Group (GONG). The
eastern filament (F1) first erupted toward the northeast. During the eruption
of F1, some plasma from F1 fell down and was injected to the North-East part of
another filament (F2), and some plasma of F1 fell down to the northern region
close to F2 and caused the plasma to brighten. Meanwhile, the North-East part
of F2 first started to be active and rise, but did not erupt finally. Then the
South-West part of F2 erupted successfully. Therefore, the F2's eruption is a
partial filament eruption. Two associated CMEs related to the eruptions were
observed by STEREO/COR1. We find two possible reasons that lead to the
instability and the eruption of F2. One main reason is that the magnetic loops
overlying the two filaments were partially opened by the eruptive F1 and
resulted in the instability of F2. The other is that the downflows from F1
might break the stability of F2.
