  We present detailed 3D modeling of a dense, coronal thick target X-ray flare
using the GX Simulator tool, photospheric magnetic measurements, and microwave
imaging and spectroscopy data. The developed model offers a remarkable
agreement between the synthesized and observed spectra and images in both X-ray
and microwave domains, which validates the entire model. The flaring loop
parameters are chosen to reproduce the emission measure, temperature, and the
nonthermal electron distribution at low energies derived from the X-ray
spectral fit, while the remaining parameters, unconstrained by the X-ray data,
are selected such as to match the microwave images and total power spectra. The
modeling suggests that the accelerated electrons are trapped in the coronal
part of the flaring loop, but away from where the magnetic field is minimal,
and, thus, demonstrates that the data are clearly inconsistent with electron
magnetic trapping in the weak diffusion regime mediated by the Coulomb
collisions. Thus, the modeling supports the interpretation of the coronal
thick-target sources as sites of electron acceleration in flares and supplies
us with a realistic 3D model with physical parameters of the acceleration
region and flaring loop.
