The use of bicoherence has proved its efficiency in the analysis of nonlinear wave interactions. The method has been adapted to interpret the results of a simulation of the beam-plasma interaction, in a case of broadband spectra, where many unstable modes can be suspected to couple. As the interacting waves exhibit different polarizations (electrostatic and electromagnetic), the bicoherence has been modified into a cross bicoherence in order to test the coupling of different field components. The visualization of the result has been designed in order to evidence the couplings in terms of efficiency (high bicoherence) and energy (high power). The application of this method to the simulation results shows that quadratic wave interactions are effective; new helpful information is stressed in order to interpret the observed growth of large-scale magnetic fluctuations.¿ 1997 American Geophysical Union