Cyclotron resonance in a pure electron plasma column.

Abstract

We demonstrate experimentally the effects of plasma rotation and particle thermal velocities on cyclotron resonance in a long cylindrical pure electron plasma column of low density (${\mathrm{\ensuremath{\omega}}}_{\mathit{p}}^{2}$\ensuremath{\ll}${\mathrm{\ensuremath{\omega}}}_{\mathit{c}}^{2}$). A single m=1 mode (${\mathit{e}}^{\mathit{i}\mathit{m}\mathrm{\ensuremath{\theta}}\mathrm{\ensuremath{-}}\mathit{i}\mathrm{\ensuremath{\omega}}\mathit{t}}$) is found whose frequency \ensuremath{\omega} is down-shifted from ${\mathrm{\ensuremath{\omega}}}_{\mathit{c}}$=eB/${\mathit{m}}_{\mathit{e}}$ by an amount equal to the low-frequency diocotron mode frequency (〈${\mathrm{\ensuremath{\omega}}}_{\mathit{p}}^{2}$〉/2${\mathrm{\ensuremath{\omega}}}_{\mathit{c}}$). For m=2,3,4,. . . sets of modes are found which are Doppler shifted upward from ${\mathrm{\ensuremath{\omega}}}_{\mathit{c}}$. We explain these as radially trapped and azimuthally propagating Bernstein modes.