Chaotic magnetic field lines and spontaneous development of current sheets

Abstract

The performed magnetohydrodynamic simulations aim to assess the influence of chaotic magnetic field lines on spontaneous generation of current sheets in an evolving viscous magnetofluid with infinite electrical conductivity. Suitable non-force-free initial fields having chaotic magnetic field lines are constructed by superposing two Arnold-Beltrami-Childress magnetic fields. The construction is such that the superposed field is devoid of any three or two-dimensional magnetic nulls, which are potential sites of current sheet development. Consequently, the notion of spontaneity can be attributed to any current sheet generated by the evolving magnetofluid. Moreover, to ensure the development to be spontaneous, the simulations are performed in congruence with Parker's magnetostatic theorem which necessitates an attainment of a terminal quasi-steady state and maintenance of flux-freezing to high fidelity. Importantly, the paper establishes spontaneous onset of volume distributed current sheets to be positively proportional to the strength of chaos in magnetic field lines. Evolution of more chaotic field lines is found to develop stronger current sheets which are more volume distributed. These localized current sheets are characterized by intense volume current density and hence a large electric field in the presence of magnetic diffusivity. An interesting scenario then develops, where more chaotic field lines can accelerate charged particles to greater kinetic energies than the field lines which are less chaotic.