On cyclotron waves in a bounded magnetoplasma

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Abstract
The paper presents a study of the cyclotron waves in a plasma column enclosed in a conducting cylinder and placed in an axial static magnetic field. The cutoff frequencies of the waves are investigated with special reference to the role of the plasma radius a in the wave propagation. The cyclotron modes discussed cover all the possible types, namely, circularly symmetric Com modes and asymmetric Cnm modes with n?1, each Cnm mode being split into two, designated as C−nm and C+nm modes, corresponding to two different polarizations of the field components. The upper and lower limits of the cutoff frequencies of the various modes as a tends to zero and infinity, respectively, are derived. It is found that cyclotron modes can broadly be divided into the following two categories: (1) C+n1 modes, the limiting cutoff frequencies of which are the electron cyclotron frequency ωce and lower hybrid frequency ωlh, and (2) modes other than C+n1 modes, the limiting frequencies being the upper hydrid frequency ωuh and a frequency ω0 which is a function of electron and ion plasma frequencies, ωpe and ωpi, as well as electron and ion cyclotron frequencies, ωce and ωci. The modes belonging to the first category represent, in all cases, forward waves while those of the second category may represent backward or forward waves, depending essentially on a if ωpe and ωce are kept constant. The critical radii at which the change takes place for the lowest‐order modes are derived. The effect of plasma ions on the propagation of the C+n1 modes is found to be considerable if a is sufficiently large. For other modes the effect can be considerable if both a and ωce have sufficiently high values.