Excitation and conversion of electromagnetic waves in pulsar magnetospheres.

We demonstrate that nonlinear decay of obliquely propagating Langmuir waves into Langmuir and Alfvén waves (L --> L' + A) is possible in a one-dimensional, highly relativistic, streaming pair plasma. Such a plasma may be in the magnetospheres of pulsars. It is shown that the characteristic frequency of generated Alfvén waves is much less than the frequency of Langmuir waves and may be consistent with the observational data on the radio emission of pulsars.