Quasistatic theory of ion-cyclotron heating of plasmas in open magnetic confinement systems

The quasiclassical (WKB) approximation usually cannot be applied to the theoretical description of ion cyclotron resonance heating of plasmas in open magnetic confinement systems, since the wavelength of the high-frequency (HF) forcing oscillations is comparable to or larger than the radius of the plasma. Therefore, in this paper the authors discuss an alternative approach: the quasistatic approximation, which is applicable when the forcing frequency is lower than all the magnetosonic oscillation eigenfrequencies. The quasiclassical and quasistatic approximations complement one another, and together they cover the entire range of forcing frequencies used for heating. In this paper they calculate the impedance of a loop antenna that excites forcing oscillations with azimuthal wave number m = 0 in the plasma, an also the HF power absorbed, within the framework of the quasistatic approximation. They discuss three heating mechanisms: cyclotron absorption of the HF oscillations by heavy or light (low-density) impurity ions, ions, excitation of slow magnetosonic and ion-ion hybrid oscillations at the Alfven resonance, and Cherenkov absorption by electrons. We analyze both the collisionless and strongly collisional heating regimes, and demonstrate the high efficiency of these schemes for plasma heating