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

Abstract

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 β e ?> = 0.25 and ion-to-electron mass ratio m i ?> / m e ?> = 400 is carried out on a domain cube of dimension L &ohgr; pi ?> /c = 5.12 where &ohgr; pi ?> is the ion plasma frequency. The simulations begin with a range of dimensionless fluctuating field energy densities, ϵ o ?> , 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 B o ; ?> the ion energy gain is weaker and is preferentially in directions perpendicular to B o ?> . The important new results here are that, over 0.01 < ϵ o ?> < 0.25, the maximum rate of electron heating scales approximately as ϵ o ?> , and the maximum rate of ion heating scales approximately as ϵ o 1.5 ?> . A second ensemble of simulations at ϵ o ?> = 0.10 and β e ?> = 0.25 shows that, over 25 < m i ?> / m e ?> < 1836, the ratio of the maximum ion heating rate to the maximum electron heating rate scales approximately as m e ?> / m i ?> .