Waves in Magnetosheath Jets—Classification and the Search for Generation Mechanisms Using MMS Burst Mode Data

Abstract

Magnetosheath jets are localized dynamic pressure enhancements in the magnetosheath. We make use of the high time resolution burst mode data of the Magnetospheric Multiscale mission for an analysis of waves in plasmas associated with three magnetosheath jets. We find both electromagnetic and electrostatic waves over the frequency range from 0 to 4 kHz that can be probed by the instruments on board the MMS spacecraft. At high frequencies we find electrostatic solitary waves, electron acoustic waves, and whistler waves. Electron acoustic waves and whistler waves show the typical properties expected from theory assuming approximations of a homogeneous plasma and linearity. In addition, 0.2 Hz waves in the magnetic field, 1 Hz electromagnetic waves, and lower hybrid waves are observed. For these waves the approximation of a homogeneous plasma does not hold anymore and the observed waves show properties from several different basic wave modes. In addition, we investigate how the various types of waves are generated. We show evidence that, the 1 Hz waves are connected to gradients in the density and magnetic field. The whistler waves are generated by a butterfly‐shaped pitch‐angle distribution and the electron acoustic waves by a cold electron population. The lower hybrid waves are probably generated by currents at the boundary of the jets. As for the other waves we can only speculate about the generation mechanism due to limitations of the instruments. Studying waves in jets will help to address the microphysics in jets which can help to understand the evolution of jets better.

Extremely Distant Magnetopause Locations Caused by Magnetosheath Jets

“…A first step in this direction is a case study of different wave emissions inside and in the vicinity of jets by Krämer et al. (2023) that contributes to understanding the microphysics of the jets with motivation to gain a knowledge about their evolution and formation.…”

“…For example, Katsavrias et al (2021) report significant enhancements of Pi2 pulsation activity connected with the sunward flows in the magnetosheath. A first step in this direction is a case study of different wave emissions inside and in the vicinity of jets by Krämer et al (2023) that contributes to understanding the microphysics of the jets with motivation to gain a knowledge about their evolution and formation.…”

Cluster: List of plasma jets in the subsolar magnetosheath

“…Their scale sizes are in the order of 1 R E (Gunell et al, 2014;Plaschke et al, 2020), and they have to persist for several minutes to reach the magnetopause. Furthermore, there have been recent studies about waves at jets, e.g., whistler waves due to butterfly pitch angle distributions (Krämer et al, 2023) or lower hybrid waves that may be generated due to density gradients at the edges of jets (Gunell et al, 2014). On the other hand, jet evolution on its way through the magnetosheath is still poorly understood.…”

Unveiling the 3D Structure of Magnetosheath Jets

“…They also contribute to various fundamental plasma processes, such as wave generation (Karlsson et al, 2018;B. Wang et al, 2022;Krämer et al, 2023), plasma acceleration (Lavraud et al, 2007;Liu et al, 2019), and magnetic reconnection (Phan et al, 2007;Hietala et al, 2018;Ng et al, 2021). Beyond their impact on the magnetosphere, these jets exhibit observable effects even on the ground, including geomagnetic disturbances, enhancements in ionospheric outflow, and dayside aurora (Hietala et al, 2012;Han et al, 2016;B.…”