  An opposite polarity dusty plasma system (containing a few micron size
massive opposite polarity dust species and singly charged ion species following
Boltzmann law) is considered. The nature of dust-acoustic (DA) wave
electrostatic and self-gravitational potentials are correctly found by the
numerical analysis of two coupled second-order nonlinear differential equations
for electrostatic and self-gravitational potentials associated with the DA
waves in such an opposite polarity dusty plasma medium. These coupled nonlinear
differential equations are derived from the continuity and momentum equations
for positive and negative dust species, and the Boltzmann law for ion species.
The basic features of the DA wave self-gravitational potential are compared
with that of the DA wave electrostatic potential. The relevance of our results
to space and laboratory opposite polarity dusty plasma systems is mentioned.
