Dwarf novae in quiescence: the relationship between disk evaporation and accretion onto a white dwarf.

We investigate the structure of the corona above the cool accretion disk in a cataclysmic binary system. As already shown in an earlier investigation material flows from the disk through the corona on to the compact star, thus evaporating the accretion disk and creating a hole around the white dwarf. In the present work we study in detail how effective the evaporation works at different distances from the white dwarf. A one-zone model was used as before, because the most important changes happen close to the inner edge of the disk. We discuss the link between the rotating accretion disk corona and the thermal boundary layer close to the white dwarf. The physics of the thermal layer has similarity with the layer at the bottom of the accretion disk corona, where the temperature rises from photospheric to coronal values. For the white dwarf boundary layer gravity has to be taken into account. The vertical structure is computed. The material accreting via the disk corona on to the white dwarf causes the X-rays and UV radiation observed from dwarf novae during quiescience.