1994A&A...284..637B

By using a treatment of saturated heat conduction developed in a previous paper, we study the penetration of electrons from a hot medium into a nearby cold medium, and the behaviour of the resulting heat flux. The time evolution of the process is also investigated. If radiative losses cannot balance Coulomb heating, a heat front propagates into the cold medium. Instead, an equilibrium profile is asymptotically reached in case radiative losses are able to quench Coulomb heating. Large scale hydrodynamics become important only at a later time, and may end with the disruption of the cloud. We then apply these results to the evaporation of clouds in young supernova remnants, and typical time scales for the evolution are derived, in agreement with observations. In this scenario the heat front is likely to move into the cloud faster than the secondary shock driven by the pressure of the intercloud medium. An implication, that requires further investigations, is that in this case the optical emission may not be due to recombination in a radiative shock, but to a gradual heating by the conduction front. A preliminary comparative discussion with previous models of "suprathermal evaporation" is also presented.