The ISM clumps engulfed by the SNR would be left relatively intact after the passage of the shock and slowly evaporate in the interior via thermal conduction. This solution reproduces the observed brightness distribution and temperature profiles for several thermal-composite remnants, assuming a convenient initial energy for the SN and adequate density contrast for the surroundings. An alternative scenario was presented by Shelton . This model assumes that saturated thermal conduction transports energy outwards from the very hot center.
Thermal conduction reduces the central temperature and the temperature gradient.
Since pressure is unaffected, the central density is increased to compensate, and the density gradient decreases. This model was successfully applied by Shelton to explain W 44 observations.