The fate of langmuir waves: Wind and stereo observations

The earth’s foreshock has a rich collection of Langmuir waves useful for the study of their generating instabilities as well as processes important in electromagnetic wave generation as in type II and type III solar radio bursts. These processes include parametric decay to another Langmuir wave and an ion acoustic wave, possible other parametric processes, condensation to a long wavelength state when such decay is no longer possible, and trapping in preexisting density depressions. Some processes suggested in the past, such as collapse, for example, have been shown by Wind observations not to take place in the Earth’s foreshock. In his paper studies of Langmuir waves after they have been generated are presented.