Broadband Electrostatic Waves Behind Dipolarization Front: Observations and Analyses. Issue 12 (21st December 2021)

• Record Type: Journal Article
• Authors: Guo, Z. Z.; Fu, H. S.; Cao, J. B.; Yu, Y.; Chen, Z. Z.; Xu, Y.; Liu, Y. Y.; Wang, Z.; Chen, G.; Xiong, X.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 12(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-21
• Subjects: dipolarization front -- temperature anisotropy -- broadband electrostatic waves; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA029900
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Using high‐resolution MMS data, we report the observations of broadband electrostatic waves associated with parallel electron temperature anisotropy ( T e ∥ > T e ⊥ ${T}_{e{\Vert} } > {T}_{e\perp }$ ) 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 Q = F ∥ / F ⊥ − 1 $Q={F}_{{\Vert} }/{F}_{\perp }-1$, where F $F$ is phase space densities at each energy. By performing correlation analyses between parallel flux anisotropies ( Q s $Qs$ ) and power spectral densities (PSDs) of these waves, we find that: (a) Q s $Qs$ in 0.8–20 keV are positively correlated with the parallel electric field fluctuations in 50–3, 000 Hz; (b) Q s $Qs$ 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. Plain Language Summary: Dipolarization fronts (DFs), the leading edge of the earthward high speed plasma jets in the Earth's magnetotail, are characterized by a sudden increase of northward magnetic field. It plays crucial roles in global flux transport and energy conversion during substorm. Behind DFs, there are various plasma waves related to the electron temperature anisotropies. For example, the whistler waves excited by perpendicular electron temperature anisotropy have been widely observed. However, few studies on the relationship between parallel electron temperature anisotropy and waves are reported behind DFs. In this study, using MMS data, we report the observations of broadband electrostatic waves associated with parallel electron temperature anisotropy behind a DF, and quantitatively investigate the correlation between parallel electron anisotropies and power spectral densities of these waves. Key Points: Broadband electrostatic waves are observed behind a dipolarization front These waves include electrostatic solitary waves and electron cyclotron waves These electrostatic fluctuations are positively correlated with electron parallel flux anisotropies in 0.8–20 keV