Dependence of 3D Self-correlation Level Contours on the Scales in the Inertial Range of Solar Wind Turbulence

TL;DR

This study analyzes how 3D self-correlation level contours of magnetic field and velocity vary with scale in the inertial range of solar wind turbulence, revealing isotropy in magnetic fields and anisotropy in velocity.

Contribution

First to examine the scale dependence of 3D self-correlation contours in the inertial range of solar wind turbulence using Wind spacecraft data.

Findings

Magnetic field self-correlation contours are isotropic in the inertial range.

Velocity self-correlation contours show 2D anisotropy with elongation perpendicular to the magnetic field.

Differences between magnetic field and velocity provide new insights into solar wind turbulence.

Abstract

The self-correlation level contours at the 1010 cm scale reveal a 3D isotropic feature in the slow solar wind and a quasi-anisotropic feature in the fast solar wind. However, the 1010 cm scale is approximately near the lowfrequency break (outer scale of turbulence cascade), especially in the fast wind. How the self-correlation level contours behave with dependence on the scales in the inertial range of solar wind turbulence remains unknown. Here we present the 3D self-correlation function level contours and their dependence on the scales in the inertial range for the first time. We use data at 1 au from instruments on the Wind spacecraft in the period 2005-2018. We show the 3D isotropic self-correlation level contours of the magnetic field in the inertial range of both slow and fast solar wind turbulence. We also find that the self-correlation level contours of the velocity in the inertial range present 2D anisotropy with an elongation in the perpendicular direction and 2D isotropy in the plane perpendicular to the mean magnetic field. These results indicate differences between the magnetic field and the velocity, providing new clues to interpret the solar wind turbulence on the inertial scale.