Interaction of magnetic reconnection and Kelvin‐Helmholtz modes for large magnetic shear: 2. Reconnection trigger

Abstract

Citation:Ma, X., A. Otto, and P. A. Delamere (2014) Abstract A typical property of magnetopause reconnection is a significant perpendicular shear flow due to the fast streaming magnetosheath plasma. Therefore, the magnetopause represents a large magnetic and flow shear boundary during periods of southward interplanetary magnetic field, which can be unstable to Kelvin-Helmholtz (KH) modes and to magnetic reconnection. A series of local three-dimensional MHD and Hall MHD simulations is carried out to investigate the interaction of reconnection and nonlinear KH waves considering magnetic reconnection as the primary process. It is demonstrated that the onset reconnection causes a thinning of the shear flow layer, thereby generating small wavelength KH modes. In turn, the growing KH modes modify the current layer width, which modulate the diffusion regions, increase the local reconnection rates, and generate field-aligned currents. The simulation results imply a limitation of total amount of open flux likely caused by nonlinear saturation of KH growth and the associated diffusion. It is also demonstrated that the reconnection rate maximizes for conditions that allow a strong nonlinear evolution of KH waves, i.e., fast shear flow and limited guide magnetic field. The presence of Hall physics increases the reconnection rate in the early stage; however, the maximum reconnection rate and the total amount of open flux at saturation are the same as in the MHD case.

Particle-in-cell simulation study of the scaling of asymmetric magnetic reconnection with in-plane flow shear

“…The effect of outof-plane flow has been studied [44][45][46][47] . Incorporating diamagnetic effects into the theoretical predictions 48,49 should be the subject of future work.…”

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

“…This study investigates the process where a nonlinear ideal instability (i.e., the KH instability) triggers a secondary nonideal evolution (i.e., the tearing mode or more precisely component magnetic reconnection), which requires the presence of nonzero resistivity only in the diffusion region. Hence, we applied a current‐dependent resistivity model, which is given by (Nykyri & Otto, , ; Ma et al, , ). Here H ( x ) is the Heaviside unit step function (Arfken et al, ), the critical current density, j c , is set to be 0.4, and 1.4, the coefficient η 0 =0.2, and background resistivity, η b , is 0.002.…”

Juno observations of large‐scale compressions of Jupiter's dawnside magnetopause

“…However, Ebert et al [] recently observed Hall magnetic field structures and Alfvénic jets at Jupiter's magnetopause near the dawn terminator, indicating that reconnection may yet play a role in mass transport. Kelvin‐Helmholtz vortices, which are observed at other planetary magnetospheres [ Hasegawa et al , ; Masters et al , ; Delamere et al , ; Sundberg et al , ; Gershman et al , ; Kavosi and Raeder , ; Ma et al , , , ], are expected to be present, but these structures at Jupiter have not yet been reported. Finally, low‐frequency MHD fluctuations with periods up to ~100 s have been observed inside of Jupiter's magnetosphere and in the magnetopause boundary layer (MPBL) [ Tsurutani et al , ].…”