Kinetic Scale Density Fluctuations in the Solar Wind

TL;DR

This paper explores kinetic scale density fluctuations in the solar wind, emphasizing their role in heliospheric heating, and demonstrates measurement techniques and spectral analysis consistent with turbulence models.

Contribution

It introduces a method to measure kinetic scale density fluctuations via spacecraft potential and compares observed spectra with theoretical turbulence models.

Findings

Density spectrum shape matches cascade model predictions.

Ion scale flattening explained by combined passive fluctuations and kinetic Alfven wave turbulence.

Measurement technique effectively captures kinetic scale density fluctuations.

Abstract

We motivate the importance of studying kinetic scale turbulence for understanding the macroscopic properties of the heliosphere, such as the heating of the solar wind. We then discuss the technique by which kinetic scale density fluctuations can be measured using the spacecraft potential, including a calculation of the timescale for the spacecraft potential to react to the density changes. Finally, we compare the shape of the density spectrum at ion scales to theoretical predictions based on a cascade model for kinetic turbulence. We conclude that the shape of the spectrum, including the ion scale flattening, can be captured by the sum of passive density fluctuations at large scales and kinetic Alfven wave turbulence at small scales.