Contribution of cyclotron-resonant damping to kinetic dissipation of interplanetary turbulence

We examine some implications of inertial range and dissipation range correlation and spectral analyses extracted from 33 intervals of Wind magnetic field data. When field polarity and signatures of cross helicity and magnetic helicity are examined, most of the datasets suggest some role of cyclotron resonant dissipative processes involving thermal protons. We postulate that an active spectral cascade into the dissipation range is balanced by a combination of cyclotron-resonant and non-cyclotron-resonant kinetic dissipation mechanisms, of which only the former induces a magnetic helicity signature. A rate balance theory, constrained by the data, suggests that the ratio of the two mechanisms is of order unity. While highly simplified, this approach appears to account for several observed features, and explains why complete cyclotron absorption, and the corresponding pure magnetic helicity signature, is usually not observed.