  We investigate the acceleration of charged particles (both electrons and
protons) at collisionless shocks predicted to exist in the vicinity of solar
flares. The existence of standing termination shocks has been examined by flare
models and numerical simulations e.g., Shibata,Forbes. We study electron
energization by numerically integrating the equations of motion of a large
number of test-particle electrons in the time-dependent two-dimensional
electric and magnetic fields generated from hybrid simulations (kinetic ions
and fluid electron) using parameters typical of the solar flare plasma
environment. The shock is produced by injecting plasma flow toward a rigid
piston. Large-scale magnetic fluctuations -- known to exist in plasmas and
known to have important effects on the nonthermal electron acceleration at
shocks -- are also included in our simulations. For the parameters
characteristic of the flaring region, our calculations suggest that the
termination shock formed in the reconnection outflow region (above post-flare
loops) could accelerate electrons to a kinetic energy of a few MeV within 100
ion cyclotron periods, which is of the order of a millisecond. Given a
sufficient turbulence amplitude level ($\delta B^2/B_0^2 \sim 0.3$), about 10%
of thermal test-particle electrons are accelerated to more than 15 keV. We find
that protons are also accelerated, but not to as high energy in the available
time and the energy spectra are considerably steeper than that of the electrons
for the parameters used in our simulations. Our results are qualitatively
consistent with the observed hard X-ray emissions in solar flares.
