WHISTLER TURBULENCE HEATING OF ELECTRONS AND IONS: THREE-DIMENSIONAL PARTICLE-IN-CELL SIMULATIONS

Abstract

The decay of whistler turbulence in a collisionless, homogeneous, magnetized plasma is studied using three-dimensional particle-in-cell simulations. The simulations are initialized with a narrowband, relatively isotropic distribution of long wavelength whistler modes. A first ensemble of simulations at electron beta  = 0.25 and ion-to-electron mass ratio /  = 400 is carried out on a domain cube of dimension / c  = 5.12 where is the ion plasma frequency. The simulations begin with a range of dimensionless fluctuating field energy densities, , and follow the fluctuations as they cascade to broadband, anisotropic turbulence which dissipates at shorter wavelengths, heating both electrons and ions. The electron heating is stronger and preferentially parallel/antiparallel to the background magnetic field the ion energy gain is weaker and is preferentially in directions perpendicular to . The important new results here are that, over 0.01 < < 0.25, the maximum rate of electron heating scales approximately as , and the maximum rate of ion heating scales approximately as . A second ensemble of simulations at  = 0.10 and  = 0.25 shows that, over 25 < / < 1836, the ratio of the maximum ion heating rate to the maximum electron heating rate scales approximately as / .