Guided Waves on Cold Non-uniform Plasma Columns†

Some general features of the problem of guided waves on cold plasma columns in an axial magnetic field which are transversely non-uniform are examined. It is shown that a marked increase in the damping of the cold-plasma space-charge waves can occur in those frequency regions where a type of ‘resonance’ exists in the plasma. Two specific examples are treated to illustrate the general ideas: A plasma Blab with a trapezoidal density distribution in the absence of a magnetic field, and a circular column with a parabolic density distribution in an axial magnetic field. The possible relevance of the general results to several experimental observations of an anomalously large damping of guided waves is discussed.