OBSERVATIONAL CONSTRAINTS ON THE ROLE OF CYCLOTRON DAMPING AND KINETIC ALFVÉN WAVES IN THE SOLAR WIND

Certain few intervals with high-β plasma (ratio of gas pressure to magnetic pressure) have been interpreted as containing turbulent fluctuations with wave vectors that are confined to very oblique angles with respect to the mean magnetic field. The fluctuations are theorized to be Kinetic Alfvén Waves (KAWs) engaged in an energy cascade that dissipates primarily at electron scales. Dissipation by ions, and by cyclotron damping in particular, is argued to be minimal to non-existent. This interpretation is not supported, generally, by the analysis of larger data sets using other data analysis methods. These prior studies, however, were not conducted for specific β ranges. In this study, we reconsider the analysis for a moderately large set of high-β intervals. The analysis includes magnetic variance, the Bieber ratio test, the cross-helicity versus magnetic helicity correlation, and the implied break frequency versus angle relationship. In our analysis, the results do not support the exclusive KAW interpretation as applied generally to solar wind intervals of high-β while the results do support the presence of cyclotron damping at a significant level.