On the Theory of ICR Heating by the Magnetic Beach Method

Abstract

Current interest in ion cyclotron resonance (ICR) heating by the magnetic beach method is motivated by the experiments carried out with the VASIMR plasma thruster. The method implies excitation of Alfvén eigenmodes of a plasma column (or a plasma jet in the case of plasma thruster) outside the ICR zone. In the present work, it is shown that, under conditions typical of, e.g., plasma thrusters, most of the electromagnetic energy deposited in the plasma can be transferred to the so-called Alfvén continuum, rather than to the discrete spectrum of Alfvén eigenmodes. Due to the phenomenon of the Alfvén resonance, continuous-spectrum oscillations transform into short-wavelength lower hybrid oscillations, which differ from the Alfvén oscillations in their polarization. These oscillations efficiently interact with electrons, thereby heating them.