  Filament eruptions often result in flares and coronal mass ejections (CMEs).
Most studies attribute the filament eruptions to their instabilities or
magnetic reconnection. In this study, we report a unique observation of a
filament eruption whose initiation process has not been reported before. This
large-scale filament, with a length of about 360 Mm crossing an active region,
is forced to erupted by two small-scale erupting filaments pushing out from
below. This process of multi-filament eruption results in an M6.4 flare in the
active region NOAA 13229 on 25th February 2023. The whole process can be
divided into three stages: the eruptions of two active-region filaments F1 and
F2; the interactions between the erupting F1, F2, and the large-scale filament
F3; and the eruption of F3. Though this multi-filament eruption occurs near the
northwest limb of the solar disk, it produces a strong halo CME that causes a
significant geomagnetic disturbance. Our observations present a new filament
eruption mechanism, in which the initial kinetic energy of the eruption is
obtained from and transported to by other erupting structures. This event
provides us a unique insight into the dynamics of multi-filament eruptions and
their corresponding effects on the interplanetary space.
