  We perform MHD modeling of a single bright coronal loop to include the
interaction with a non-uniform magnetic field. The field is stressed by random
footpoint rotation in the central region and its energy is dissipated into
heating by growing currents through anomalous magnetic diffusivity that
switches on in the corona above a current density threshold. We model an entire
single magnetic flux tube, in the solar atmosphere extending from the high-beta
chromosphere to the low-beta corona through the steep transition region. The
magnetic field expands from the chromosphere to the corona. The maximum
resolution is ~30 km. We obtain an overall evolution typical of loop models and
realistic loop emission in the EUV and X-ray bands. The plasma confined in the
flux tube is heated to active region temperatures (~3 MK) after ~2/3 hr.
Upflows from the chromosphere up to ~100 km/s fill the core of the flux tube to
densities above 10^9 cm^-3. More heating is released in the low corona than the
high corona and is finely structured both in space and time.
