Abstract
Abstract. The Earth's magnetosphere and solar wind environment is a laboratory of excellence for the study of the physics of collisionless magnetic reconnection. At low latitude magnetopause, magnetic reconnection develops as a secondary instability due to the stretching of magnetic field lines advected by large scale Kelvin-Helmholtz vortices. In particular, reconnection takes place in the sheared magnetic layer that forms between adjacent vortices during vortex pairing. The process generates magnetic islands with typical size of the order of the ion inertial length, much smaller than the MHD scale of the vortices and much larger than the electron inertial length. The process of reconnection and island formation sets up spontaneously, without any need for special boundary conditions or initial conditions, and independently of the initial in-plane magnetic field topology, whether homogeneous or sheared.
Highlights
In many astrophysical and laboratory systems with β-values of the order of unity, the large scale plasma dynamics is governed by the interplay between plasma flow and magnetic field
Solar wind interaction with the magnetosphere at low latitude magnetopause is an outstanding problem in space plasma physics, in particular concerning the understanding of the non-linear collisionless dynamics of a sheared flow in the presence of a magnetic field
It has been generally assumed that the specific small scale process is “unimportant” for the global evolution provided reconnection develops, the large scale evolution being more or less unique
Summary
In many astrophysical and laboratory systems with β-values of the order of unity, the large scale plasma dynamics is governed by the interplay between plasma flow and magnetic field. The second approach, instead, makes use of external drivers, as for example the injection of MHD waves, in order to develop reconnection in a “stable” initial magnetic configuration These studies have shed light on the fundamental aspect characterizing reconnection, i.e. the conditions and the plasma regimes that allow the possibility of demagnetizing the electrons inside very thin “critical” layers, in other words letting the magnetic field lines slip away in such “critical” regions from the electron fluid. A strong mixing is observed during northward magnetic field periods leading to an increase of the plasma content in the outer magnetosphere even greater than during southward configurations It has been proposed, that the shear flow between the solar wind and the magnetosphere drives the formation of Kelvin-Helmholtz (KH) vortices that tend to pair in the non-linear phase (Belmont and Chanteur, 1989; Miura, 1997). We present some recent results obtained using the same model as in Faganello et al (2008c) but taking an initial in-plane sheared magnetic field
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