On Alfvén wave heating and transit time magnetic pumping in the guiding-centre model of a plasma

Abstract

A theoretical investigation of the use of the guiding-centre plasma (GCP) model to describe RF absorption in a non-uniform plasma is made. The absorption is studied in the transit time magnetic pumping (TTMP) and Alfvén wave frequency ranges. An externally applied RF source is assumed with a frequency range lying in the continuous spectra of the linearized GCP equations of motion describing the plasma dynamics. Absorption arises from local resonances which characterize the continuum. The total GCP spectrum is composed of components which are found in ideal MHD and Vlasov kinetic theory. The effective impedance of an external coil assembly is calculated for tokamak and scyllac configurations in both the TTMP and Alfvén wave regimes. Very optimistic results are obtained for both configurations indicating that effective coupling of an external source to the plasma is possible in the Alfvén wave regime. The results also show that better coupling is possible with Alfvén frequencies than with TTMP. The results are compared with similar calculations using only the ideal MHD-model; similarities and deviations are pointed out.