Plasma Transport Driven by the Three‐Dimensional Kelvin‐Helmholtz Instability

Abstract

It has been well demonstrated that the nonlinear Kelvin‐Helmholtz (KH) instability plays a critical role for the solar wind interaction with the Earth's magnetosphere. Although the two‐dimensional KH instability has been fully explored during the past decades, more and more studies show the fundamental difference between the two‐ and three‐dimensional KH instability. For northward interplanetary magnetic field (IMF) conditions, the nonlinear KH wave that is localized in the vicinity of the equatorial plane can dramatically bend the magnetic field line, generating strong antiparallel magnetic field components at high latitudes in both North and South Hemispheres, which satisfy the onset condition for magnetic reconnection. This high‐latitude double reconnection process can exchange the portion of magnetosheath and magnetospheric flux tubes between those two reconnection sites. This study used a high‐resolution 3‐D magnetohydrodynamic simulation to demonstrate that nonlinear KH waves can generate a large amount of double‐reconnected flux during the northward IMF condition, which can efficiently transport the plasma with a high diffusion coefficient of 1 × 1010 m2 s−1 for typical magnetopause conditions at the Earth. The presence of the magnetic field component along the shear flow direction not only decreases the KH growth rate but also causes north‐south asymmetry, which generates more open flux and reduces the efficiency of the plasma transport process.

On the Dawn‐Dusk Asymmetry of the Kelvin‐Helmholtz Instability Between 2007 and 2013

“…Another key process at the magnetopause is Kelvin‐Helmholtz instability (KHI), which is driven by the free energy of velocity shear. Because KHI can produce transport of mass, momentum, and energy across boundary layers (Cowee et al, ; Ma et al, , ; Matsumoto & Hoshino, ; Miura, ; Nakamura et al, ; Nykyri & Otto, , ; Otto & Fairfield, ; Thomas & Winske, ), it can play a significant role in magnetospheric dynamics. KHI can be stabilized by plasma compressibility and the magnetic tension force (Miura & Pritchett, ).…”

Comparison Between Fluid Simulation With Test Particles and Hybrid Simulation for the Kelvin‐Helmholtz Instability

“…Thus, a careful quantification of plasma transport must define a boundary between the MSH and the MSP based on the magnetic field configuration first and then compare the mass change within these regions (e.g., Ma et al, 2017;Sorathia et al, 2017). In the current test parameter regime, Hall MHD with test particles and hybrid simulation give almost identical particle mixing rates.…”

“…In reality, the KH wave vector is mainly along the most unstable direction. Ma et al (2017) estimated the mass transport rate with asymmetric density by identifying double-reconnected flux though fluid parcel and magnetic field line tracing and found the mass transport rate can reach 10 10 m2/s. However, such singularity is caused by 2-D geometry, which does not exist in 3-D geometry.…”

“…It can be responsible for the transport of momentum and energy (Miura, 1984;Pu & Kivelson, 1983). In addition, the KH instability can trigger secondary instabilities (e.g., reconnection and wave-particle interaction) in the nonlinear stage to break the frozen-in condition, which transports plasma, flux tube entropy, and magnetic flux (Delamere et al, 2011;Delamere et al, 2018;Ma et al, 2014aMa et al, , 2014bMa et al, 2017;Nykyri & Otto, 2004;Ohsawa et al, 1976;Otto & Fairfield, 2000). Furthermore, several nonadiabatic heating mechanisms are expected to be attributed to the KH instability and the associated secondary instability (e.g., Masson & Nykyri, 2018;Moore et al, 2016).…”

“…Simulation studies from magnetohydrodynamics (MHD) to particle-in-cell (PIC) simulation show a large range of transport rates from 10 9 to 10 10 m 2 /s for Earth's magnetopause environments (Cowee et al, 2009(Cowee et al, , 2010Delamere et al, 2011;Miura, 1984;Ma et al, 2017;Nykyri & Otto, 2001, 2004Nakamura et al, 2017). Simulation studies from magnetohydrodynamics (MHD) to particle-in-cell (PIC) simulation show a large range of transport rates from 10 9 to 10 10 m 2 /s for Earth's magnetopause environments (Cowee et al, 2009(Cowee et al, , 2010Delamere et al, 2011;Miura, 1984;Ma et al, 2017;Nykyri & Otto, 2001, 2004Nakamura et al, 2017).…”