Interaction of magnetic reconnection and Kelvin‐Helmholtz modes for large magnetic shear: 1. Kelvin‐Helmholtz trigger

Abstract

At the Earth's magnetopause, both magnetic reconnection and the Kelvin-Helmholtz (KH) instability can operate simultaneously for southward interplanetary magnetic field conditions. The dynamic evolution of such a system can be expected to depend on the importance of KH wave evolution versus reconnection and therefore on the respective initial perturbations. In this study, a series of local three-dimensional MHD and Hall MHD simulations are carried out to investigate the situation where the Kelvin-Helmholtz instability is initially the primary process. It is demonstrated that magnetic reconnection is driven and strongly modified by nonlinear KH waves. The highest reconnection rate is close to the Petschek rate, but the total open flux is limited by the size of the nonlinear KH wave. Most of the total open magnetic flux has no flux rope structure and originates from reconnection at thin current layers which connect adjacent vortices. In contrast, complex flux ropes generated by patchy reconnection within the KH vortices dominate the vicinity of the equatorial plane; however, the associated open flux with flux ropes is a minor contribution to the total open flux. Although the presence of Hall physics leads to a fast early increase of the reconnection rate, the maximum reconnection rate and the total amount of open magnetic 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.…”

Characterization of high-intensity, long-duration continuous auroral activity (HILDCAA) events using recurrence quantification analysis

“…On the other hand, during HILDCAA events, the two fundamental electrodynamics interactions (magnetic reconnection and viscous interaction) with a transfer of energy and particles are indeed happening. In principle, interplanetary phenomena producing both of those coupling mechanisms, as processes examined in Ma et al (2014), concern the mechanisms related to interplanetary Alfvén waves. In this kind of occurrence, magnetic disturbances can be detected by magnetometers at the polar regions as the HILDCAA events.…”

“…Therefore, those RQA features can be useful for other study purposes. The RQA method gives a clear indication of the dynamics to be evaluated by magneto-hydrodynamics simulations, as developed by Ma et al (2014) or Chen et al (2004), to understand the processes involved in a transfer of energy and particles into the magnetosphere-ionosphere system.…”

Particle Orbits at the Magnetopause: Kelvin‐Helmholtz Induced Trapping

“…Indeed, the "high-latitude" areas (top and bottom edges of the periodic box in the vertical z direction) are more stable with respect to the KHI than the domain closer to the z = 0 plane, due to variations of the velocity and magnetic field magnitude. In the rolling-up stage (t MHD = 400, Figure 1b), the magnetic field lines relax around the crests of the waves, called spines of the KHI by Ma et al (2014), while they are compressed in the lower density (light blue) area of the waves. Thus, vortices emerging near the z = 0 plane locally advect the field lines, while the part that is further away remains unperturbed for a longer time.…”