Short wavelength electrostatic wave measurement using MMS spacecraft

TL;DR

This paper presents a new method based on spin-plane interferometry for reliable 3D electric field measurement of short-wavelength electrostatic waves observed by MMS, applied to ion acoustic waves in the solar wind.

Contribution

It introduces a novel measurement technique for short-wavelength electrostatic waves and applies it to solar wind data to determine wave vectors and wavelengths.

Findings

Wave propagation is predominantly field-aligned.

Wavelengths peak around 100 m.

Waves are between 10 and 20 Debye lengths.

Abstract

Determination of the wave mode of short-wavelength electrostatic waves along with their generation mechanism requires reliable measurement of the wave electric field. We investigate the reliability of the electric field measurement for short-wavelength waves observed by MMS. We develop a method, based on spin-plane interferometry, to reliably determine the full 3D wave vector of the observed waves. We test the method on synthetic data and then apply it to ion acoustic wave bursts measured in situ in the solar wind. By studying the statistical properties of ion acoustic waves in the solar wind we retrieve the known results that the wave propagation is predominantly field-aligned. We also determine the wavelength of the waves. We find that the distribution peaks at around 100 m, which when normalized to the Debye length corresponds to scales between 10 and 20 Debye lengths.