Abstracts submitted by Lapo Bettarini

Tearing-triggered instabilities and reconnection mechanisms in the solar environment

Lapo Bettarini [1]; Simone Landi [1]; Marco Velli [1,3]

[1] Dipartimento di Astronomia, UniversitĂ di Firenze; [3] JPL, California Institute of Technology

Magnetic shear driven instabilities play a major role both in the dynamics of astrophysical objects and, in particular, in the evolution of several structures in the solar atmosphere. Although magnetic energy conversion by reconnection in two dimensions is relatively well understood, in three dimensions the magnetic topology and the MHD dynamics can be highly complex and also the related reconnection mechanism. Moreover, the presence of a sheared flow, and so the resulting stream + current sheet interaction, introduces a further degree of complexity.A detailed analysis of this class of problems has urged us to develop new premising numerical schemes.Considering two different perturbed current-sheet equilibrium configurations, a pressure-balanced and a force-free configuration, we present the three dimensional evolution of a tearing-driven current-sheet in the framework of compressible and resistive Magnetohydrodynamics. Furthermore, the first results on the 3D problem of combined magnetic and velocity shear driven instabilities are shown considering also a variable geometry of the basic fields. In order to understand resistive instabilities, secondary instabilities (in presence even of a guide field) and magnetic reconnection with the requirement of a detailed description of dissipation driven instabilities in the linear phase, several ingredients are needed. In addition, magnetic reconnection in the coronal and heliospheric plasma is often controlled by kinetic effects, such as the Hall term, which introduce dispersion and add to the number of different wave-modes carried by the plasma. These terms are important as they decrease the dependence of the growth rate on the Reynolds numbers, but have not been used universally for coronal and heliospheric physics until today.