We reconsider the theory for three-wave interactions in cold plasmas. In particular, we demonstrate that previously overlooked formulations of the general theory are highly useful when deriving concrete expressions for specific cases. We also point out that many previous results deduced directly from the basic plasma equations contain inappropriate approximations leading to unphysical results. Finally, generalizations to more elaborate plasma models containing, for example, kinetic effects are

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... iven. General results for a cold plasma In order to demonstrate the usefulness of our approach we shall, for simplicity, consider the resonant interaction between three waves with frequencies ω j (j = 1, 2, 3) and wavevectors k j , with ω 3 = ω 1 + ω 2 and k 3 = k 1 + k 2 , in a cold https://www.cambridge.org/core/terms. https://doi.