Wave Amplification by Interaction with a Stream of Electrons

A discussion is given of the propagation of plane electromagnetic waves in a uniform, ionized medium, in which the electrons possess a mean drift velocity. The treatment is based on the general theory developed by V. A. Bailey. It is shown that, for frequencies below a certain critical frequency (of the same order as the electron plasma frequency), one of the eight possible waves in general grows in amplitude as it progresses through the medium. The relation of this result to the theories of solar noise and of the traveling wave tube amplifier is discussed.