VISCOSITY AND ION SOUND IN SUPERDENSE PLASMAS

Plasma states with high values of the ion-ion interaction parameter ar e examined, including the regions of the liquid and crystalline states . It is shown that near the melting point the time-drift mechanism for viscosity is supplanted by the vacancy mechanism and the correspondin g rise in viscosity sharply narrows the region of phase space occupied by the viscous acoustic mode. In this way the conditions for propagat ion of nonviscous sound arise. It is dissipated at high wave numbers b y Joule heating.