The Occurrence and Prevalence of Time Domain Structures in the Kelvin-Helmholtz Instability at Different Positions Along the Earth’s Magnetospheric Flanks

Abstract

The Kelvin-Helmholtz instability (KHI) is thought to be an important driver for mass, momentum, and energy transfer between the solar wind and magnetosphere. This can occur through global-scale “viscous-like” interactions, as well as through local kinetic processes such as magnetic reconnection and turbulence. An important aspect of these kinetic processes for the dynamics of particles is the electric field parallel to the background magnetic field. Parallel electric field structures that can occur in the KHI include the reconnection electric field of high guide field reconnection, large amplitude ion acoustic waves, as well as time domain structures (TDS) such as double layers and electrostatic solitary waves. In this study, we present a survey of parallel electric field structures observed during three Kelvin Helmholtz events observed by NASA’s Magnetospheric Multiscale (MMS), each at different positions along the magnetosphere’s dusk flank. Using data from MMS’s on-board solitary wave detector (SWD) algorithm, we statistically investigate the occurrence of TDS within the KHI events. We find that early in the KHI development, TDS typically occur in regions with strong field-aligned currents (FACs) on the magnetospheric side of the vortices. Further down the flanks, as the vortices become more rolled up, the prevalence of large electric currents decreases, as well as the prevalence of SWDs. These results suggest that as the instability develops and vortices grow in size along the flanks, kinetic-scale activity becomes less prevalent.

The Occurrence and Prevalence of Magnetic Reconnection in the Kelvin‐Helmholtz Instability Under Various Solar Wind Conditions

“…Table 1 shows a list of the 12 events identified for study. Some of these events, including the ones on 09/08/2015, 09/27/2015, and 09/26/2017 have been reported in previous studies (Eriksson, Lavraud, et al, 2016;Tang et al, 2018;Wilder et al, 2021). The mean position of MMS in the X-Y GSE plane is shown in Figure 1a.…”

“…(2016) and Figure 2 from Wilder et al. (2021) shows a visualization of what compressed current sheets look like and what features were used to visually identify them. In summary, visual inspection was used to look for a traversal by the spacecraft from magnetospheric to magnetosheath‐like plasma and a reversal in the B Y or B X GSE component.…”

Multi-scale observations of the magnetopause Kelvin–Helmholtz waves during southward IMF

“…Considering past kinetic studies of the KHI during northward IMF and the subsequent small-scale physics such as turbulence, 17,60,61 reconnection, 10,62 and kinetic waves, 18,63,64 this MMS event can serve as an ideal case study for such high-resolution research studies of the KHI during southward IMF.…”

Density and Magnetic Field Asymmetric Kelvin‐Helmholtz Instability

“…The Kelvin‐Helmholtz (KH) instability is driven by a large sheared flow (Chandrasekhar, 1961), which is an important physical mechanism for the viscous‐like interaction between the Earth's magnetosphere (MSP) and the solar wind (SW) (Axford, 1964; Axford & Hines, 1961). There are lots of in‐situ observation events during both north‐ and southward interplanetary magnetic field (IMF) conditions at low‐latitudes (Blasl et al., 2022; Eriksson, Lavraud, et al., 2016; Henry et al., 2017; Hwang et al., 2011; Kavosi et al., 2023; Li et al., 2013, 2016, 2023; Rice et al., 2022; Wilder et al., 2023; Yan et al., 2014, 2022), as well as at high latitudes with IMF mostly along the dawn or dusk direction (Hwang et al., 2012; Ma et al., 2016; Nykyri et al., 2021). Kavosi and Raeder (2015) shows that for Earth's magnetopause, KH waves occur about 19% of the time.…”