Kinetic Scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere

TL;DR

This paper introduces a new high-cadence measurement technique using the Parker Solar Probe's Flux Angle mode to analyze kinetic scale turbulence in the solar wind, providing detailed spectral features of cross helicity and residual energy.

Contribution

It presents the first application of the Flux Angle mode for kinetic scale turbulence analysis, enabling rapid measurements of phase space density fluctuations close to the Sun.

Findings

Spectral index of turbulence measured at 0.174 AU

Residual energy and cross helicity computed during the encounter

Technique allows detailed kinetic scale turbulence characterization

Abstract

In this Paper, we present the first results from the Flux Angle operation mode of the Faraday Cup instrument onboard Parker Solar Probe. The Flux Angle mode allows rapid measurements of phase space density fluctuations close to the peak of the proton velocity distribution function with a cadence of 293 Hz. This approach provides an invaluable tool for understanding kinetic scale turbulence in the solar wind and solar corona. We describe a technique to convert the phase space density fluctuations into vector velocity components and compute several turbulence parameters such as spectral index, residual energy and cross helicity during two intervals the Flux Angle mode was used in Parker Solar Probe's first encounter at 0.174 AU distance from the Sun.