EXCITATION OF CAPILLARY WAVES BY LONGER WAVES

At low wind speeds the shortest capillary waves appear to be generated hydrodynamically and not by the wind. This phenomenon is investigated using a Hamiltonian representation of the surface wave dynamics. A pe rturbation technique of Kolmogorov is used to transform away non-reson ant, nonlinear interactions. Resonant interactions are treated by the Hasselmann transport equation, applied to the transformed variables. C alculated spectra show reasonable agreement with the observations of J ahne & Riemer (1990).