Coarse-graining and nonlocal processes in proton cyclotron resonant interactions

Coarse-grained information from a hybrid simulation show that previously developed quasifluid equations of state capture some aspects of proton cyclotron resonant interactions for parallel propagation in a low beta plasma. Direct kinetic information is used as a closure for the information exchanged with the higher-order moment quantities. The coarse-graining procedure involves averaging over many proton-inertial lengths and looking at long time scales associated with the wave envelopes. By use of the coarse-graining prior to statistical analysis, the anticorrelations predicted by the equations of state are very high for both the single resonant wave case and for a broadband spectrum centered on a resonant wave. These anticorrelations are also consistent with what one expects from a single particle orbit analysis. A similar analysis, but done without the prior averaging procedures, shows no relevant correlations, and no simple dynamics emerges from the kinetic data in this case. A comparison is made with a model based on quasilinear theory. These results suggest that, in addition to simply taking velocity moments of particle distributions, the proper averaging of kinetic information over space and time scales lying below the range accessible to a fluid model can be essential to its success. (C) 1998 American Institute of Physics.