  The phenomenon of peripheral coronal loop contraction during solar flares and
eruptions, recently discovered in observations, gradually intrigues solar
physicists. However, its underlying physical mechanism is still uncertain. One
is Hudson (2000)'s implosion conjecture which attributes it to magnetic
pressure reduction in the magnetic energy liberation core, while other
researchers proposed alternative explanations. In previous observational
studies we also note the disappearance of peripheral shrinking loops in the
late phase, of which there is a lack of investigation and interpretation. In
this paper, we exploit a full MHD simulation of solar eruption to study the
causes of the two phenomena. It is found that the loop motion in the periphery
is well correlated with magnetic energy accumulation and dissipation in the
core, and the loop shrinkage is caused by a more significant reduction in
magnetic pressure gradient force than in magnetic tension force, consistent
with the implosion conjecture. The peripheral contracting loops in the late
phase act as inflow to reconnect with central erupting structures, which
destroys their identities and naturally explains their disappearance. We also
propose a positive feedback between the peripheral magnetic reconnection and
the central eruption.
