On the Generation of Pi2 Pulsations due to Plasma Flow Patterns Around Magnetosheath Jets

Abstract

The Earth's magnetosheath-the region downstream of the bow shock-contains decelerated and compressed solar wind plasma exhibiting strong fluctuations in velocity, density, and associated magnetic field. Especially the magnetosheath downstream of the quasi-parallel shock, where the angle between the interplanetary magnetic field (IMF) and the bow shock normal vector is less than 45°, is particularly turbulent even during steady solar wind conditions. Furthermore, it is permeated both by waves that have been transmitted through the bow shock, as well as by fluctuations that have been generated locally (Blanco-Cano et al., 2006;Lucek et al., 2005).Upstream of the quasi-parallel bow shock, solar wind ions are reflected forming a region called the ion foreshock which is filled by backstreaming ion populations. These ions can generate various wave modes and-more often than not-ULF waves (Blanco-Cano et al., 2020) which is suggested to be transmitted, through the magnetosheath, into the magnetosphere (Clausen et al., 2009). On the other hand, at the quasi-perpendicular bow shock, the initially reflected ions are mostly heated in the direction perpendicular to the magnetic field exhibiting enhanced temperature anisotropy. This anisotropy can generate transverse ion cyclotron (IC) waves with   1 and/or compressive, nonpropagating mirror mode waves with   1 (Génot et al., 2009). Jets in the magnetosheath are transient localized enhancements in dynamic pressure typically caused by increases in plasma velocity, density, or both (

On Magnetosheath Jet Kinetic Structure and Plasma Properties

“…The VDF profiles, observed at the initial stage of the jet (t 1 ), can be effectively modeled as two drifting Maxwellian distributions with different velocities. Such configurations can in principle drive a series of waves and explain previous observations made with respect to wave generation and variations in the magnetic field (Gunell et al, 2014;Karlsson et al, 2018;Katsavrias et al, 2021;Plaschke et al, 2017Plaschke et al, , 2020 in proximity to jets. Such wave generation and complex interaction that we demonstrate could also have an effect on the overall characterization of the MSH region regarding waves, current sheets and turbulence related phenomena typically observed (e.g., Gingell et al, 2021;H.…”

“…outer magnetosphere environment (Archer et al, 2019(Archer et al, , 2021Katsavrias et al, 2021) and even have effects on the inner magnetosphere and ionosphere (Hietala et al, 2012;Norenius et al, 2021;Wang et al, 2018).…”

On the phenomenology of magnetosheath jets with insight from theory, modelling, numerical simulations and observations by Cluster spacecraft

“…One prominent feature is the occurrence of bursts of irregular magnetic field pulsations PI1-2 recorded on ground for a broad range of local times. Parkhomov et al, 2021;Parkhomov et al, 2022) argue that the pulsations observed by ground observatories have properties similar to the pulsations detected in-situ in the vicinity of magnetosheath jets (Katsavriasi et al, 2021). It is argued that the propagation of the pulsations to the ground, along closed magnetic field lines, proves the irregularities, which are the source of pulsations, moved impulsively from the magnetosheath into the magnetosphere, across the magnetopause (Echim and Lemaire, 2000).…”

The Magnetopause Deformation Indicated by Fast Cold Ion Motion

“…Similarly, HSJs with local pressure enhancements can induce obvious inward magnetopause motion, following by possible subsequent magnetopause rebound (Shue et al., 2009; Plaschke et al., 2018; X. Wang et al., 2023) and the observed magnetopause normal can significantly differ from model predictions (Escoubet et al., 2020). Accompanied by the magnetopause deformation, magnetic reconnection can be triggered at the magnetopause (Hietala et al., 2018; Ng et al., 2021), waves can be generated in the magnetosphere (Katsavrias et al., 2021), and the ionosphere can have some response as well (B. Wang et al., 2018). Therefore, investigations of the magnetopause deformation caused by these pressure perturbation structures are very helpful to understand the solar wind‐magnetosphere coupling process, as their occurrence rates are not rare (Plaschke et al., 2016; Schwartz et al., 2000).…”