  Twisted coronal loops should be ubiquitous in the solar corona. Twisted
magnetic fields contain excess magnetic energy, which can be released during
magnetic reconnection, causing solar flares. The aim of this work is to
investigate magnetic reconnection, and particle acceleration and transport in
kink-unstable twisted coronal loops, with a focus on the effects of
resistivity, loop geometry and atmospheric stratification. Another aim is to
perform forward-modelling of bremsstrahlung emission and determine the
structure of hard X-ray sources. We use a combination of magnetohydrodynamic
(MHD) and test-particle methods. First, the evolution of the kinking coronal
loop is considered using resistive MHD model, incorporating atmospheric
stratification and loop curvature. Then, the obtained electric and magnetic
fields and density distributions are used to calculate electron and proton
trajectories using a guiding-centre approximation, taking into account Coulomb
collisions. It is shown that electric fields in twisted coronal loops can
effectively accelerate protons and electrons to energies up to 10 MeV.
High-energy particles have hard, nearly power-law energy spectra. The volume
occupied by high-energy particles demonstrates radial expansion, which results
in the expansion of the visible hard X-ray loop and a gradual increase in hard
X-ray footpoint area. Synthesised hard X-ray emission reveals strong footpoint
sources and the extended coronal source, whose intensity strongly depends on
the coronal loop density.
