  Coronal implosions - the convergence motion of plasmas and entrained magnetic
field in the corona due to a reduction in magnetic pressure - can help to
locate and track sites of magnetic energy release or redistribution during
solar flares and eruptions. We report here on the analysis of a well-observed
implosion in the form of an arcade contraction associated with a filament
eruption, during the C3.5 flare SOL2013-06-19T07:29. A sequence of events
including magnetic flux-rope instability and distortion, followed by filament
eruption and arcade implosion, lead us to conclude that the implosion arises
from the transfer of magnetic energy from beneath the arcade as part of the
global magnetic instability, rather than due to local magnetic energy
dissipation in the flare. The observed net contraction of the imploding loops,
which is found also in nonlinear force-free field extrapolations, reflects a
permanent reduction of magnetic energy underneath the arcade. This event shows
that, in addition to resulting in expansion or eruption of overlying field,
flux-rope instability can also simultaneously implode unopened field due to
magnetic energy transfer. It demonstrates the "partial opening of the field"
scenario, which is one of the ways in 3D to produce a magnetic eruption without
violating the Aly-Sturrock hypothesis. In the framework of this observation we
also propose a unification of three main concepts for active region magnetic
evolution, namely the metastable eruption model, the implosion conjecture, and
the standard "CSHKP" flare model.
