Short‐Wavelength Electrostatic Wave Measurement Using MMS Spacecraft

Abstract

AbstractDetermination of the wave mode of short‐wavelength electrostatic waves along with their generation mechanism requires reliable measurement of the wave electric field. We show that for such waves the electric field measured by Magnetospheric MultiScale becomes unreliable when the wavelength is close to the probe‐to‐probe separation. We develop a method, based on spin‐plane interferometry, to reliably determine the full three‐dimensional wave vector of the observed waves. We test the method on synthetic data and then apply it to ion acoustic wave bursts measured 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 nominal value is around 100 m, which when normalized to the Debye length corresponds to scales between 10 and 20 Debye lengths.