  We study the relationship between implosive motions in a solar flare, and the
energy redistribution in the form of oscillatory structures and particle
acceleration. The flare SOL2012-03-09T03:53 (M6.4) shows clear evidence for an
irreversible (stepwise) coronal implosion. Extreme-ultraviolet (EUV) images
show at least four groups of coronal loops at different heights overlying the
flaring core undergoing fast contraction during the impulsive phase of the
flare. These contractions start around a minute after the flare onset, and the
rate of contraction is closely associated with the intensity of the hard X-ray
(HXR) and microwave emissions. They also seem to have a close relationship with
the dimming associated with the formation of the Coronal Mass Ejection (CME)
and a global EUV wave. Several studies now have detected contracting motions in
the corona during solar flares that can be interpreted as the implosion
necessary to release energy. Our results confirm this, and tighten the
association with the flare impulsive phase. We add to the phenomenology by
noting the presence of oscillatory variations revealed by GOES soft X-rays
(SXR) and spatially-integrated EUV emission at 94 and 335 {\AA}. We identify
pulsations of $\approx 60$ seconds in SXR and EUV data, which we interpret as
persistent, semi-regular compressions of the flaring core region which modulate
the plasma temperature and emission measure. The loop oscillations, observed
over a large region, also allow us to provide rough estimates of the energy
temporarily stored in the eigenmodes of the active-region structure as it
approaches its new equilibrium.
