Magnetosperic Multiscale (MMS) observation of plasma velocity-space cascade: Hermite representation and theory

TL;DR

This paper uses high-resolution MMS measurements to analyze plasma turbulence in Earth's magnetosheath, revealing a velocity-space cascade characterized by a Hermite transform and a Kolmogorov-like scaling theory, advancing understanding of space plasma turbulence.

Contribution

It introduces a Hermite transform analysis of plasma velocity distributions and develops a Kolmogorov-like theory for velocity-space cascades in space plasmas.

Findings

Power law distribution of Hermite moments observed

Scaling theory agrees with MMS data

Suggests new approach for plasma turbulence studies

Abstract

Plasma turbulence is investigated using high-resolution ion velocity distributions measured by the Magnetospheric Multiscale Mission (MMS) in the Earth's magnetosheath. The particle distribution is highly structured, suggesting a cascade-like process in velocity space. This complex velocity space structure is investigated using a three-dimensional Hermite transform that reveals a power law distribution of moments. In analogy to hydrodynamics, a Kolmogorov approach leads directly to a range of predictions for this phase-space cascade. The scaling theory is in agreement with observations, suggesting a new path for the study of plasma turbulence in weakly collisional space and astrophysical plasmas.