Stars as Laboratories for Fundamental Physics - MPP Theory Group

598 Appendix D
with the mass density in units of g cm −3 and T 8 = T/10 8 K. Recall that
for a single nuclear species Y e = Z/A (atomic weight A).
The plasma is weakly coupled for Γ ∼ < 1, it is in the liquid metal
phase for 1 ∼ < Γ < 178, and forms a body-centered cubic lattice for
Γ > 178 (Slattery, Doolen, and DeWitt 1980, 1982). Debye screening
by the ions is appropriate for a weakly coupled plasma; otherwise the
Debye approximation for the ion-ion correlations is misleading. Contours
for Γ in the ρ-T -plane are shown in Fig. D.6. For the purposes
of this book, a strongly coupled plasma occurs only in the interior of
white dwarfs.
Fig. D.6. Contours for the plasma coupling parameter Γ. Also shown are
the loci of the stellar models of Fig. D.1 which had to be shifted relative
to each other according to the nuclear charge Z relevant for each chemical
composition.
D.1.6
Summary
The characteristic plasma properties for a number of typical astrophysical
sites that are important in the main body of the book are summarized
in Tab. D.1.