Broadband Electrostatic Waves Behind Dipolarization Front: Observations and Analyses

Abstract

AbstractUsing high‐resolution MMS data, we report the observations of broadband electrostatic waves associated with parallel electron temperature anisotropy () behind a dipolarization front (DF). These electrostatic waves include electrostatic solitary waves and electron cyclotron waves. To quantify electron anisotropy, we define the parallel flux anisotropy parameter , where is phase space densities at each energy. By performing correlation analyses between parallel flux anisotropies () and power spectral densities (PSDs) of these waves, we find that: (a) in 0.8–20 keV are positively correlated with the parallel electric field fluctuations in 50–3,000 Hz; (b) in 0.8–20 keV are positively correlated with perpendicular electric field fluctuations in all frequency ranges; (c) the correlation between parallel flux anisotropies and perpendicular electric field fluctuations is more significant in this case. We also discuss the possibility of electron firehose instability and wave–particle interactions. Our study promotes the understanding of the properties and dynamics of DFs.