Comparing Energy Transfer in High and Low Frequency Alfvenic Turbulence

We employ field-particle correlations, the velocity-resolved time average of the Lorentz term in the Vlasov equation, to characterize the mechanisms responsible for energy transfer in two distinct turbulent simulations. Using these correlations, we determine the characteristic velocities associated with secular transfer of energy between electromagnetic fields and particle velocity distributions; different mechanisms will preferentially transfer energy to particles in different regions of velocity space. This tool is applied to a driven, low-frequency turbulence simulation and a higher frequency decaying turbulence simulation. In the low-frequency system, modeled using the gyrokinetic code AstroGK, the energy transfer is strongly resonant, with resonant velocities agreeing with linear predictions. In the high-frequency system, modeled using the hybrid code HVM, signatures of cyclotron damping are seen. As this method can be applied to single point observations, it is an ideal tool for application to systems with data only available at a few points within the domain where it can help elucidate the mechanisms operating in those systems.