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 whic h ensures limited variations of thermodynamical variables across grid points. The code provides an accurate description of the dynamics of t he chromosphere-corona transition region, in spite of the very steep t emperature and density gradients, even during flare-like transients. T he new model can be used to synthesize, together with X-ray emission, the optically thin emission originating from the transition region,; m ainly in the EUV band. Here we show sample results.