  We propose a mechanism for quasi-periodic oscillations of both coronal mass
ejections (CMEs) and flare loops as related to magnetic reconnection in
eruptive solar flares. We perform two-dimensional numerical MHD simulations of
magnetic flux rope eruption, with three different values of the global
Lundquist number. In the low Lundquist number run, no oscillatory behavior is
found. In the moderate Lunquist number run, on the other hand, quasi-periodic
oscillations are excited both at the bottom of the flux rope and at the flare
loop-top. In the high Lundquist number run, quasi-periodic oscillations are
also excited; in the meanwhile, the dynamics become turbulent due to the
formation of multiple plasmoids in the reconnection current sheet. In high and
moderate Lundquist number runs, thin reconnection jet collide with the flux
rope bottom or flare loop-top and dig them deeply. Steep oblique shocks are
formed as termination shocks where reconnection jet is bent (rather than
decelerated) in horizontal direction, resulting in supersonic back-flows. The
structure becomes unstable, and quasi-periodic oscillation of supersonic
back-flows appear at locally confined high-beta region at both the flux rope
bottom and flare loop-top. We compare the observational characteristics of
quasi-periodic oscillations in erupting flux ropes, post-CME current sheets,
flare ribbons and light curves, with corresponding dynamical structures found
in our simulation.
