PHASE COUPLING IN LANGMUIR WAVE-PACKETS - POSSIBLE EVIDENCE OF 3-WAVEINTERACTIONS IN THE UPSTREAM SOLAR-WIND

Some theories of the generation of 2 omega(pe) radiation, in the upstr eam solar wind, invoke the notion of nonlinear wave-wave interactions. We present observations, from the WIND spacecraft, of an event in the upstream solar wind with first and second harmonic emissions. The bic oherence spectrum of this event shows coherence amongst components tha t suggest three-wave interactions of the type described in (Cairns and Melrose, 1985). We discuss this result and its theoretical context.