Spectra of Diffusion, Dispersion, and Dissipation for Kinetic Alfvénic and Compressive Turbulence: Comparison between Kinetic Theory and Measurements from MMS

Abstract

Abstract We analyze measurements from Magnetospheric Multiscale mission to provide the spectra related with diffusion, dispersion, and dissipation, all of which are compared with predictions from plasma theory. This work is one example of magnetosheath turbulence, which is complex and diverse and includes more wave modes than the kinetic Alfvénic wave (KAW) mode studied here. The counter-propagation of KAW is identified from the polarities of cross-correlation spectra: CC(N e, ∣B∣), CC(V e⊥, B ⊥), CC(V e∥, B ∥), and CC(N e, V e∥). We propose the concepts of turbulence ion and electron diffusion ranges (T-IDRs and T-EDRs) and identify them practically based on the ratio between electric field power spectral densities in different reference frames: PSD( )/PSD(δ E global) and PSD( )/PSD(δ E global). The outer scales of the T-IDR and T-EDR are observed to be at the wavenumber of kd i ∼ 0.2 and kd e ∼ 0.1, where d i and d e are the proton and electron inertial lengths, respectively. The signatures of positive dispersion related to the Hall effect are illustrated observationally and reproduced theoretically with flat PSD(δ E global) and steep PSD(δ B ), as well as a bifurcation between PSD(δ V i) and PSD(δ V e). We calculate the dissipation rate spectra, , which clearly show the commencement of dissipation around kd i ∼ 1. We find that the dissipation in this case is mainly converted to electron parallel kinetic energy, responsible for the electron thermal anisotropy with T e,∥/T e,⊥ > 1. The “3D” (diffusion, dispersion, and dissipation) characteristics of kinetic Alfvénic and compressive plasma turbulence are therefore summarized as follows: positive dispersion due to the Hall effect appears in the T-IDR, while dominant parallel dissipation with energy transferred to electrons occurs mainly in the T-EDR.