Spectral anisotropy of solar wind turbulence in the inertial range and dissipation range

Abstract

Wavelet analysis is a tool that can simultaneously analyze spacecraft data in both time and frequency. This enables the magnetic energy spectrum (trace spectrum) to be measured for different angles between the local mean magnetic field B₀ and the direction of the mean flow within a single data set. Examples obtained around solar minimum using Ulysses data at high latitudes and Stereo data for high-speed streams in the ecliptic plane show that the spectral exponent in the inertial range varies nearly monotonically from approximately 1.6 when B₀ is perpendicular to the flow to 2.0 when B₀ is parallel to the flow, roughly consistent with anisotropic theories of incompressible MHD turbulence. This and other new information about the 3D wavector spectrum of solar wind fluctuations in the inertial range and the dissipation range are briefly discussed.