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

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. Plain Language Summary: There is a constant plasma flow from the sun, the solar wind. The Earth's magnetic field deflects the solar wind as it flows toward Earth. As the solar wind plasma approaches Earth it gets decelerated and heated at the bow shock. Earthward of the bow shock, the magnetosheath is located where the flow diverges around Earth. In the magnetosheath plasma flows that are denser and faster than normal can sometimes be observed, so called magnetosheath jets. We investigate waves in plasmas in these magnetosheath jets and how they are generated. Studying these waves will help to understand the interaction of magnetosheath jets with their environment. Key Points: MMS burst mode data is used to investigate waves in, and in the vicinity of, magnetosheath jets0.2 Hz waves, 1 Hz waves, whistler waves, electron acoustic waves, lower hybrid waves, and solitary waves are observedWaves with low frequencies cannot be explained by "basic" wave modes that are derived in homogeneous plasmas [ABSTRACT FROM AUTHOR]