Kinetic Alfven Turbulence: Electron and Ion Heating by Particle-in-cell Simulations

Three-dimensional particle-in-cell simulations of the forward cascade of decaying kinetic Alfven turbulence have been carried out as an initial-value problem on a collisionless, homogeneous, magnetized, electron-ion plasma model with beta(e) = beta(i)= 0.50 and m(i)/m(e) = 100, where subscripts e and i represent electrons and ions, respectively. Initial anisotropic narrowband spectra of relatively long-wavelength modes with approximately gyrotropic distributions in k(perpendicular to) undergo a forward cascade to broadband spectra of magnetic fluctuations at shorter wavelengths. Maximum electron and ion heating rates are computed as functions of the initial fluctuating magnetic field energy density eo on the range 0.05 < epsilon(o) < 0.50. In contrast to dissipation by whistler turbulence, the maximum ion heating rate due to kinetic Alfven turbulence is substantially greater than the maximum electron heating rate. Furthermore, ion heating as well as electron heating due to kinetic Alfven turbulence scale approximately with eo. Finally, electron heating leads to anisotropies of the typeT(vertical bar vertical bar e) > T-perpendicular to e, where the parallel and perpendicular symbols refer to directions parallel and perpendicular, respectively, to the background magnetic field, whereas the heated ions remain relatively isotropic. This implies that, for the range of eo values considered, the Landau wave-particle resonance is a likely heating mechanism for the electrons and may also contribute to ion heating.