Cascade of whistler turbulence: Particle-in-cell simulations

A two-dimensional electromagnetic particle-in-cell simulation in a magnetized, homogeneous, collisionless plasma of electrons and protons has been carried out, demonstrating a forward cascade of whistler turbulence. Enhanced magnetic fluctuation spectra are initially imposed with -0.2 < k parallel to c/omega(e) < 0.2 and -0.2 < k(perpendicular to)c/omega(e) < 0.2 where the directional subscripts denote directions relative to the background magnetic field B(o) and c/omega(e) is the electron inertial length. The late-time evolution of the simulation shows a cascade of magnetic fluctuation energy to shorter wavelengths; furthermore, the spectrum is anisotropic with more fluctuation energy at a given wavenumber perpendicular to Bo than at the same wavenumber parallel to the background field. The late-time electron velocity distribution shows a magnetic-field aligned signature due to the Landau resonance of the obliquely propagating whistlers.