Science Seminars

Kinetic Aspects of the Vortex-Induced Reconnection in Collisionless Plasmas: 2D PIC Simulations

Speaker: Takuma Nakamura
Date: Thursday, Apr 12, 2012
Time: 4:00 PM to 5:00 PM
Location: LSTB-299, Auditorium

Seminar Abstract:

We investigate the reconnection process induced by the MHD-scale Kelvin-Helmholtz (KH) vortex by using 2D fully kinetic simulations. The KH vortex has long been considered as one of the most important phenomena for causing momentum and energy transport or direct plasma mixing in collisionless plasmas. In this talk, we focus on the case in which the moderate strength of the magnetic shear coexists with the velocity shear layer. Such a configuration is thought to occur on the flanks in the planetary magnetospheres such as the Earth and Mercury. We will contrast results from the symmetric and asymmetric (density jump across the layer) configurations on the evolution and the resulting transport. Past 2D MHD and two-fluid simulations showed that the flow of the KH vortex strongly compress the current sheet (the shear layer), and hence can quickly drive reconnection even in MHD-scale boundary layers. Indeed, recent in-situ observations succeeded in showing direct evidence of reconnection between flow vortices. Our recent 2D (PIC) simulations newly revealed that the so-called vortex-induced reconnection (VIR) is commonly accompanied by the multiple magnetic island formation in the current sheet compressed by the KH vortex. This multiple island formation process leads to efficient plasma mixing within the vortex as well as particle acceleration. In the asymmetric case where there is a density jump across the velocity shear layer, secondary KH waves along the edge of the vortex are generated and eventually cause turbulence within the vortex. We are also revealing that the number of islands formed in the compressed current sheet is different between the Earth’s duskside magnetopause-like and dawn-like vorticity cases. In our presentation, we will discuss relevance of these findings to the problem of the Earth’s low-latitude boundary layer (LLBL) formation.