  The equation of state (EOS) of a low-density porous substance plasma is
proposed in the form of continuous media EOS containing, as a pressure control
parameter, the degree of plasma homogenization, which is function of the
initial porous structure, as well as of the current values of plasma density
and temperature. Using the partially-homogenized-plasma EOS an approximate
analytical solution is found and numerical calculations were performed of the
problem of thermal expansion of a flat layer of porous matter. The features of
the obtained results are discussed in comparison with the case of a continuous
substance of equivalent chemical composition. The proposed equation of state is
used to analyze the experimental data on porous substance heating with laser
and X-ray pulses.
