Jets and Mirror Mode Waves in Earth's Magnetosheath

Abstract

Magnetosheath jets are localized plasma structures with high dynamic pressure which are frequently observed downstream of the Earth's bow shock. In this work we analyze Magnetospheric MultiScale magnetic field and plasma data and show that jets can be found in the quasi‐perpendicular magnetosheath in regions permeated by Mirror mode waves (MMWs). We show that structures identified as jets by their enhanced dynamic pressure can have very different internal structure, with variable signatures in magnetic field magnitude and components, velocity, and density and can be associated to ion distribution functions of various types. This suggests that jets observed in the quasi‐perpendicular magnetosheath are generated by different mechanisms. We find that jets can be related to traveling foreshocks, flux transfer events, and some have MMWs inside them. Our results suggest that some jets have a local source and their formation does not depend on upstream structures. We find that different types of ion distributions can exist inside the jets, while in some cases anisotropic distributions are present, in others counterstreaming distributions exist. We also show that for jets with MMWs inside them, ion distributions can be modulated. This highlights the importance of using ion distributions to identify and classify different types of jets.

Magnetosheath jets at Jupiter and across the solar system

“…Other than shock–discontinuity interactions, observations at Earth suggest that mirror modes, commonly found in quasi-perpendicular magnetosheath, can also contribute to the generation of jets 15 , 38 , 39 . According to a previous statistical study 40 , in the Jovian magnetosheath mirror modes were found during 62% of the time when data were available; and indeed, mirror structures had been identified around the two jets by using magnetic field data only.…”

Characteristics of Foreshock Subsolar Compressive Structures

“…Using ion-kinetic Vlasiator simulations, Suni et al (2021) show that MSH jets are related to foreshock compressive structures. The relation between foreshock structures and MSH jets is not straightforward because Blanco-Cano et al (2023) discusses the jets observed in the magnetosheath behind the quasi-perpendicular BS that have local sources and do not depend on upstream structures. Moreover, the jets in the magnetosheath are often mixed with plasmoids embedded in the flow that are created locally by reconnection in the highly turbulent environment just behind the BS (Preisser et al, 2020).…”