Solar wind turbulent spectrum from MHD to electron scales

TL;DR

This paper investigates the magnetic fluctuation spectra in the solar wind from MHD to electron scales, revealing a universal power-law at larger scales and a dissipation-related curvature at electron scales, using Cluster data.

Contribution

It provides the first detailed analysis of the turbulent spectrum from MHD to electron scales in the solar wind, highlighting the spectral curvature and the non-universality of the transition at ion scales.

Findings

Confirmation of spectral curvature indicating dissipation at electron scales

Universal power-law spectrum at MHD and ion scales

Non-universal transition from inertial to ion scales

Abstract

Turbulent spectra of magnetic fluctuations in the free solar wind are studied from MHD to electron scales using Cluster observations. We discuss the problem of the instrumental noise and its influence on the measurements at the electron scales. We confirm the presence of a curvature of the spectrum $\sim \exp{\sqrt{k\rho_e}}$ over the broad frequency range $\sim[10,100]$ Hz, indicating the presence of a dissipation. Analysis of seven spectra under different plasma conditions show clearly the presence of a quasi-universal power-law spectrum at MHD and ion scales. However, the transition from the inertial range $\sim k^{-1.7}$ to the spectrum at ion scales $\sim k^{-2.7}$ is not universal. Finally, we discuss the role of different kinetic plasma scales on the spectral shape, considering normalized dimensionless spectra.