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

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 eP , B P), and CC(N e , V eP). 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(d ¢ E i,local)/PSD(δE global) and PSD(d ¢ E e,local)/PSD(δE 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(δE global) and steep PSD(δB), as well as a bifurcation between PSD(δV i) and PSD(δV e). We calculate the dissipation rate spectra, g k (), 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,P /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.

Observational Evidence for Solar Wind Proton Heating by Ion‐Scale Turbulence

“…An analysis on the solar wind with time interval of 13.4 hr shows that the distribution of ( β ‖ p , T ⊥ p / T ‖ p ) associated with ICWs corresponds to higher T ⊥ p / T ‖ p (Telloni & Bruno, 2016). Direct measurements of the dissipation rate spectrum around ion scales in magnetosheath turbulence indicate the perpendicular heating by ICWs (He et al, 2019, 2020). In this letter, we favor the scenario of the heating by KAW turbulence because the KAW turbulence appears to be ubiquitous and has energy much higher than ICWs in the solar wind near 1 AU (He et al, 2012b).…”

Statistical Survey of Collisionless Dissipation in the Terrestrial Magnetosheath

“…In recent years, the availability of high time‐resolution data in the Earth's magnetosheath from multi‐spacecraft missions such as Cluster and MMS has enabled some of the most detailed studies of plasma turbulence carried out in any venue (Goldstein et al., 2015; He et al., 2020; Sahraoui et al., 2020). In the magnetosheath, like the solar wind, plasma moment data—velocities, densities, and temperatures—along with vector magnetic field data enable study of the turbulence cascade in a weakly collisional plasma (Andrés et al., 2019; Bandyopadhyay et al., 2018; MacBride et al., 2008; Sorriso‐Valvo et al., 2018), a problem of widespread relevance throughout the heliosphere, and elsewhere in astrophysics.…”

Multi‐Spacecraft Measurement of Anisotropic Spatial Correlation Functions at Kinetic Range in the Magnetosheath Turbulence

“…Research of turbulence embedded in magnetized space plasma has been carried out for more than 4 decades, and its characteristics are gradually revealed. Turbulence plays an essential role in the fundamental physical processes, such as energy dissipation, energy transport, and particle heating/acceleration in the plasma (e.g., Bruno & Carbone, 2013; He, Duan, et al., 2019; He et al., 2020; Huang and Sahraoui, 2019, Huang, Zhang et al., 2020; Huang et al., 2012; Sahraoui et al., 2010, 2009, 2020; Tu & Marsch, 1995; Zimbardo et al., 2010).…”