OBSERVATION OF SPONTANEOUSLY EXCITED CHAOS-LIKE ION-PLASMA OSCILLATIONS

An oscillation which behaves quite similarly to chaos under some condi tions is observed to exist among ion plasma oscillations spontaneously excited in an ion beam-plasma system. There are two different states of the system, the ''silent'' and ''chaotic'' states, sensitively depe nding on the value of a direct current (DC) voltage V-B, which determi nes the beam energy and is adopted as a control parameter here. In the chaotic state, a spontaneously excited ion plasma oscillation is obse rved to become chaotic. Here, the correlation dimension for the oscill ation in the chaotic state is calculated to be 1.64 +/- 0.22. The resu lt shows that an attractor for the oscillation has a low degree of fre edom and a noninteger dimension. (C) 1995 American Institute of Physic s.