  In order to give a basis for the structure and correlation analysis of fine
particle (dusty) plasma and colloidal suspensions, thermodynamic treatment of
mixtures of macroscopic and microscopic charged particles within the adiabatic
response of the latter is extended to include the case where the system is
finite and weakly inhomogeneous. It is shown that the effective potential for
macroscopic particles is composed of two elements: mutual Yukawa repulsion and
a confining (attractive) Yukawa potential from their `shadow' (the average
charge density of macroscopic particles multiplied by the minus sign). The
result clarifies the relation between two approaches hitherto taken where
either a parabolic one-body potential is assumed or the average distribution is
assumed to be flat with finite extension. Since the satisfaction of the charge
neutrality is largely enhanced by the existence of macroscopic particles, the
assumption of the flat electrostatic potential and therefore flat average
distribution of macroscopic particles in the domain of their existence is
expected to be closer to reality than the assumption of the parabolic potential
in that domain.
