Particle heating rate , normalized by the turbulent cascade rate , as a function of thermal velocity v _th, for an initially Maxwellian distribution function. The heating rate is measured from t = 2.5–20 L/ c _s in the fiducial simulation and is ∝ n _test/ n, where n _test/ n is the number density of test particles relative to the fluid density in the simulation. Modest pitch-angle scattering rates ν enforce isotropy and significantly enhance the turbulent heating of the plasma.