Transitions of macroscopic structures and self-induced chaos observed in plasmas by a dc hollow cathode discharge having features of nonlinear open systems.

A novel experimental investigation is presented on the connection between discontinuous transitions of macroscopic structures of plasma and self-induced chaotic oscillations characterized by the positive Lyapunov exponents lambda(L) through the period-doubling route in a dc hollow cathode discharge, which has features of nonlinear open systems. We have clarified experimentally that there appear different discharge modes accompanying the discontinuous transitions, and detailed qualitative explanations are presented about the mechanism of those transitions. It is shown that fundamental frequencies of the self-induced periodic oscillations with nonpositive lambda(L) change with the changes of discharge current, and the amplitude of chaotic oscillations with the positive lambda(L) jumps up almost one order higher than that of nonchaotic ones with the nonpositive lambda(L). The self-induced chaotic oscillations with the positive lambda(L) have been observed near two edges of discontinuous transitions of plasma structures, suggesting that the chaotic mode is associated with the discontinuous transition of macroscopic structures in some nonlinear open systems.