Marina Skender: Evolution of quasiequilibrium current sheet

Evolution of quasiequilibrium current sheet prof. Marina Skender (Univerza v Osijeku)

Magnetic reconnection is ubiquitous process in space and laboratory plasmas. A two-dimensional reconnecting current sheet is studied numerically in the MHD approach. Different simulation setups are employed in order to follow the evolution of the formed current sheet in diverse configurations: Two types of initial equilibria, Harris and force-free, two types of boundary conditions, periodic and open, with uniform and non-uniform grid set, respectively. All the simulated cases are found to exhibit qualitatively the same behaviour in which a current sheet evolves slowly through a series of quasi-equilibria; eventually it fragments and enters a phase of fast impulsive bursty reconnection. In order to gain more insight on the nature and characteristics of the instability taking place, physical characteristics of the simulated current sheet are related to its geometrical properties. The aspect ratio of the current sheet is observed to increase slowly in time up to a maximum value at which it fragments. Additional turbulence introduced to the system is shown to exhibit the same qualitative steps, but with the sooner onset of the fragmentation and at a smaller aspect ratio. Comparison with observed solar current sheets is discussed.