Triplet and beam interaction in a plasma

The interaction of three waves requires wavelength and frequency matching conditions. Without the presence of a particle beam, if the conditions are satisfied and if the frequency of the envelope is lower than the lowest frequency of the waves, they exchange energy and the evolution of the envelope of each wave is given by a constant plus a sinusoidal function. On the other hand, if a particle beam propagates within electrostatic and electromagnetic fields with no wavelength and frequency match, the energy exchange between the modes is done due to the particles. One of the modes could be amplified in this scheme. In the present work, we propose a model where a nonrelativistic particle beam propagates in a plasma within two electromagnetic modes and one electrostatic mode with wavelength and frequency matching conditions. Then, the waves are allowed to exchange energy between themselves and with the particle beam as well. We present new features in comparison to the isolated triplet interaction and to the beam-wave interaction. These features are relevant for a more realistic triplet interaction model