A new physical effect modeled by an Ikeda map depending on a monotonicallytime-varying parameter

In this paper we study the dynamics of a charged particle in a constant ext ernal magnetic field and the field due to a polarized electromagnetic wave. We observe a new phenomenon, the chaotic gun effect, which appears in the case of a sufficiently large amplitude of the wave. We show that the longit udinal component of the momentum undergoes oscillations with a chaotic modu lation of the amplitude which increases suddenly to a value which remains c onstant between two consecutive phase Larmor circles. The novel effect may be modeled by a time-regressive system associated with an Ikeda map dependi ng on a monotonically time-varying parameter.