An adaptive grid code for high resolution 1-D hydrodynamics of the solar and stellar transition region and corona

We present a new version of the Palermo-Harvard hydrodynamic model of plasma confined in coronal loops, based on a regridding algorithm which ensures limited variations of thermodynamical variables across grid points. The code provides an accurate description of the dynamics of the chromosphere-corona transition region, in spite of the very steep temperature and density gradients, even during flare-like transients. The new model can be used to synthesize, together with X-ray emission, the optically thin emission originating from the transition region,; mainly in the EUV band. Here we show sample results.