  Observations show that the mutual relationship between filament eruptions and
solar flares cannot be described in terms of an unique scenario. In some cases,
the eruption of a filament appears to trigger a flare, while in others the
observations are more consistent with magnetic reconnection that produces both
the flare observational signatures (e.g., ribbons, plasma jets, post-flare
loops, etc.) and later the destabilization and eruption of a filament. We study
an event which occurred in NOAA 8471, where a flare and the activation of (at
least) two filaments were observed on 28 February 1999. By using imaging data
acquired in the 1216, 1600, 171 and 195 \AA\ TRACE channels and by BBSO in the
continnum and in H$\alpha$, a morphological study of the event is carried out.
Using TRACE 1216 and 1600 \AA\ data, an estimate of the "pure" Ly$\alpha$ power
is obtained. The extrapolation of the magnetic field lines is done using the
SOHO/MDI magnetograms and assuming a potential field. The potential magnetic
field extrapolation indicates that the field line connectivity changes after
the flare. The event is triggered by the destabilization of a filament located
between the two polarities of a $\delta$ spot. This destabilization involves
the magnetic arcades of the active region and causes the eruption of a second
filament, that gives rise to a CME and to plasma motions over a supergranular
cell. We conclude that in this event the two filaments play an active and
decisive role, albeit in different stages of the phenomenon, in fact the
destabilization of one filament causes brightenings, reconnection and ribbons,
while the second one, whose eruption is caused by the field reconfiguration
resulting from the previous reconnection, undergoes the greatest changes and
causes the CME.
