Dynamics of drift and flute modes in linear cylindrical ECR plasma

Competitive and coexistence phenomena of a drift mode and a flute mode have been observed experimentally in linear cylindrical electron cyclotron resonance (ECR) plasmas. The drift mode is dominant in the low neutral gas pressure. The flute mode is excited and become dominant with the increase in the neutral gas pressure. The coexistence of the drift and flute modes is observed in the intermediate neutral gas pressure regime. The radial profiles of density, its gradient scale length and floating potential are different in the each regime. In the coexistence regime, the drift mode and the flute mode appear alternately in a single discharge. This competition is related to the rise and the crash of the density and its gradient, and the crash occurs inside and outside of this plasma at the same time, and density increases simultaneously outside when the density decrease abruptly in the central plasma region. (author)