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Resonances, Absorption and Linear Excitation of Cyclotron Harmonic Waves in a Discharge Plasma
Author(s) -
Prinzler H.
Publication year - 1974
Publication title -
beiträge aus der plasmaphysik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0005-8025
DOI - 10.1002/ctpp.19740140604
Subject(s) - atomic physics , excitation , lower hybrid oscillation , plasma , physics , electron , electron temperature , cyclotron , ionization , ion , quantum mechanics
Standing cyclotron harmonic waves below the second harmonic are observed using the noise radiation of a mercury discharge tube at 1465 MHz. From the positions of the Buchsbaum‐Hasegawa resonances the density profile and the electron temperature are derived, these parameters agree quite well with the behaviour of the collision‐free, magnetized plasma column. A onedimensional model applicable to our waveguide geometry is developed taking into account linear excitation of cyclotron harmonic waves by a quasistationary external field in a bounded plasma. Absorption and excitation are controlled by the scale length L 1 at the hybrid point and a coupling length l c , introduced by Eq. (20); the electron gyration radius r c , scale length L 1 , coupling length l c , and slab thickness 2a obeying the relation r c ≪ l c ≪ L 1 ≪2 a . The main absorption is caused by enhanced collisional damping at the upper hybrid region and only a small fraction being dissipated in the wave mode, though its field strength is large compared with that at the plasma boundary ( E W / E ( a ) ≈ 6). An estimation of the mean field strength within the coupling region shows, that such a low power as 1 mW/cm 2 absorbed in the hybrid region may produce fieldstrength exceeding the typical threshold values for non‐linear excitation mechanism.