Anisotropic model for resonant heating of ions by Alfvén waves

Abstract

AbstractAnisotropic heating of ions by Alfvén waves with frequency in the ion–cyclotron frequency range and propagation parallel to the magnetic field lines is investigated. First, particle–Alfvén wave interactions are quasilinearly examined from the kinetic theory in a hot multi-ion-magnetized plasma. As a result, the parallel and perpendicular heating rates of ions are derived analytically. Then, in terms of this anisotropic heating model and the dispersion relation of magnetic field-aligned left-hand polarized electromagnetic ion–cyclotron–Alfvén (EMICA) waves, the resonant heating of H, 2H, 3H, 3He, and 4He ions in a typical preheated laboratory plasma is numerically studied. It is shown that the EMICA waves can efficiently heat ions through cyclotron resonances primarily in the perpendicular direction. The perpendicular temperatures of H, 2H, 3H, 3He, and 4He increase much faster than the parallel ones. In comparison with the result from the previously developed isotropic heating model, the parallel heating by the EMICA waves is about much weaker, while the perpendicular heating is more efficient. Parameters such as density, temperature, magnetic field, wave-energy density, and ion species can affect the efficiency of the Alfvén wave heating in a similar way as shown in the isotropic heating model. The anisotropic model can be applied to explain the measurements of why O+5 and Mg+9 are heated extreme perpendicularly in solar coronal holes.