Nonlinear Effects of Helical Instability in Short Magnetized Positive Columns

概要

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The helical instability and oscillations in short positive columns immersed in longitudinal magnetic field are experimentally investigated. It was found that several higher order modes of helical instabilities begin to grow in turn with azimuthal mode number m coexisting with helical m = 1 mode as the magnetic field increases above a critical field B_c for the m = 1 mode. Helical m = 1 mode acompanies higher harmonics due to the nonlinearities above B_c. The nonlinear effects are enhanced with increasing magnetic field and carrier density. Oscillation frequency of the helix first increases with increasing magnetic field and finally decreases passing through a maximum in accordance with a nonlinear theory of Holter and Johnson. In a sufficiently short positive column, the plasma is always stable for all modes of instabilities independent of the magnetic field being in agreement with a short column theory of Timofeev.
社団法人日本物理学会の論文
1967-02-05