ON THE AMPLITUDE OF INTENSE LANGMUIR-WAVES IN THE TERRESTRIAL ELECTRON FORESHOCK

Waveforms of large-amplitude Langmuir oscillations were recorded by th e Wind spacecraft in the Earth's upstream electron foreshock region. W e present some statistics of the waveforms and discuss them in the con text of various saturation mechanisms. In particular, it is found that the value of E-peak/E-rms is not large, as previously suggested, and that the largest-amplitude Langmuir waveforms are generally somewhat s inusoidal and lack structure on small spatial scales. The measured pro bability distribution of electric field amplitude and dimensionless en ergy suggest that some stochastic process may play a role in wave gene ration. The values of dimensionless energy needed to arrest Langmuir w ave collapse occur with very small probability and the value of E-peak /E-rms for large fields suggests that, statistically, Langmuir wave co llapse is not an important process in the terrestrial foreshock.