Chromospheric Modelling of Active Regions on AU Mic

We present the results of a successful attempt in modelling H α and H β high resolution profiles of a dMe star. The object of our modelling is the chromosphere of active regions on the well known BY Draconis type star AU Mic (dM2.5e). We show that a very high transition region column density and a steep temperature gradient in the chromosphere are required to reproduce with accuracy the emission profiles of this very active star. The chromospheric structure is similar to those obtained when modelling solar flares, implying a very large and continuous chromospheric heating rate.