  The acceleration and transport of energetic electrons during solar flares is
one of the outstanding topics in solar physics. Recent X-ray and radio imaging
and spectroscopy observations have provided diagnostics of the distribution of
nonthermal electrons and suggested that, in certain flare events, electrons are
primarily accelerated in the loop-top and likely experience trapping and/or
scattering effects. By combining the focused particle transport equation with
magnetohydrodynamic (MHD) simulations of solar flares, we present a macroscopic
particle model that naturally incorporates electron acceleration and transport.
Our simulation results indicate that the physical processes such as turbulent
pitch-angle scattering can have important impacts on both electron acceleration
in the loop-top and transport in the flare loop, and their influences are
highly energy dependent. A spatial-dependent turbulent scattering with
enhancement in the loop-top can enable both efficient electron acceleration to
high energies and transport of abundant electrons to the footpoints. We further
generate spatially resolved synthetic hard X-ray (HXR) emission images and
spectra, revealing both the loop-top and footpoint HXR sources. Similar to the
observations, we show that the footpoint HXR sources are brighter and harder
than the loop-top HXR source. We suggest that the macroscopic particle model
provides new insights into understanding the connection between the observed
loop-top and footpoint nonthermal emission sources by combining the particle
model with dynamically evolving MHD simulations of solar flares.
