  In eruptive solar flares, termination shocks (TSs), formed when high-speed
reconnection outflows collide with closed dense flaring loops, are believed to
be one of the possible candidates for plasma heating and particle acceleration.
In this work, we perform resistive magnetohydrodynamic simulations in a classic
Kopp-Pneuman flare configuration to study the formation and evolution of TSs,
and analyze in detail the dynamic features of TSs and variations of the shock
strength in space and time. This research focuses on the fast reconnection
phase when plasmoids form and produce small-scale structures inside the flare
current sheet. It is found that the TS emerges once the downward outflow
colliding with closed magnetic loops becomes super-magnetosonic, and
immediately becomes highly dynamical. The morphology of a TS can be flat,
oblique, or curved depending on the detailed interactions between the
outflows/plasmoids and the highly dynamic plasma in the looptop region. The TS
becomes weaker when a plasmoid is crossing through, or may even be destroyed by
well developed plasmoids and then re-constructed above the plasmoids. We also
perform detailed statistical analysis on important physical quantities along
and across the shock front. The density and temperature ratios range from 1 to
3 across the TS front, and the pressure ratio typically has larger values up to
10. We show that weak guide fields do not strongly affect the Mach number and
compression ratios, and the TS length becomes slightly larger in the case with
thermal conduction.
