Abstract
Abstract. In a collisionless plasma, when reconnection instability takes place, strong shear flows may develop. Under appropriate conditions these shear flows become unstable to the Kelvin-Helmholtz instability. Here, we investigate the coupling between these instabilities in the framework of a four-field model. Firstly, we recover the known results in the low β limit, β being the ratio between the plasma and the magnetic pressure. We concentrate our attention on the dynamical evolution of the current density and vorticity sheets which evolve coupled together according to a laminar or a turbulent regime. A three-dimensional extension in this limit is also discussed. Secondly, we consider finite values of the β parameter, allowing for compression of the magnetic and velocity fields along the ignorable direction. We find that the current density and vorticity sheets now evolve separately. The Kelvin-Helmholtz instability involves only the vorticity field, which ends up in a turbulent regime, while the current density maintains a laminar structure.
Highlights
Magnetic reconnection is believed to be a crucial mechanism in order to explain different phenomena in laboratory as well as in astrophysical plasmas
On the other side, when electron temperature effects are taken into account, the current density and vorticity layers evolve according to a stable laminar structure
In conclusion we have investigated the coupling between magnetic reconnection and Kelvin-Helmholtz instability in the framework of the two-dimensional four-field model for collisionless regimes
Summary
Magnetic reconnection is believed to be a crucial mechanism in order to explain different phenomena in laboratory as well as in astrophysical plasmas. On the other side, when electron temperature effects are taken into account, the current density and vorticity layers evolve according to a stable laminar structure This different behavior has been explained in terms of the evolution of the invariants of the system, that undergo a phase mixing process in the presence of finite electron temperature (Grasso et al, 2001). We recover these results, adopting the more general four-field model. We find that the vorticity layers undergo a Kelvin-Helmholtz instability, while the current density layers evolve according to a laminar structure This twofold behavior will be explained in terms of the invariants of the model.
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