Gap solitary wave coexisting with bistable steady waves

A new kind of solitary waves is found coexisting with bistable steady waves in driven drift-wave system. The energies of these steady waves distribute in the gap between that of the bistable steady waves. The gap state is a combined result of the carrier steady wave and the soliton-like structure of perturbation wave trapped by the carrier. The effect of trapped structure is to reduce the 'potential well' of carrier wave. (C) 1997 Elsevier Science B.V.