Kinetic range spectral features of cross-helicity using MMS

TL;DR

This study analyzes the spectral features of cross-helicity in the solar wind and magnetosheath using MMS data, revealing how ion velocity and magnetic field correlations transition from fluid-like to kinetic behavior.

Contribution

It provides new insights into the scale-dependent behavior of cross-helicity and alignment in space plasmas using high-resolution spacecraft data.

Findings

Signatures of alignment at large scales

Alignment destroyed at kinetic scales due to proton demagnetization

Transition from magnetofluid to kinetic behavior observed

Abstract

We study spectral features of ion velocity and magnetic field correlations in the solar wind and in the magnetosheath using data from the Magnetospheric Multi-Scale (MMS) spacecraft. High resolution MMS observations enable the study of transition of these correlations between their magnetofluid character at larger scales into the sub-proton kinetic range, previously unstudied in spacecraft data. Cross-helicity, angular alignment and energy partitioning is examined over a suit- able range of scales, employing measurements based on the Taylor frozen-in approximation as well as direct two-spacecraft correlation measurements. The results demonstrate signatures of alignment at large scales. As kinetic scales are approached, the alignment between v and b is destroyed by demagnetization of protons.