The interaction between unstable waves has been investigated in a beam-plasma system under conditions such that nonlinear wave-particle interactions are negligible. At small wave amplitudes the results can be interpreted in terms of a simple three-wave decay process; at large amplitudes the situation is dominated by multiple wave coupling that leads to generation of satellite waves.

• Received 7 September 1971

DOI:https://doi.org/10.1103/PhysRevLett.27.1263