Role of electron-scale processes in collisionless magnetic reconnection
De rol van processen op electronschaal in het botsingsvrije magnetische reconnectieregime
Divin, Andrey; S0198602
Many phenomena in space plasmas are characterized by rapid conversion of magnetic field energy accumulated in stressed flux tubes, into kinetic and thermal energy of plasma. The efficient energy release occurs when the magnetic field lines tear and reconnect again, hence the process called `magnetic reconnection'. It appears in various plasmas; it is a nearly universal plasma process and plays a major role in solar wind-magnetosphere interaction, CME initiation, solar flares, in astrophysical and laboratory plasmas. In many space plasmas of interest collisions between separate particles can be neglected. In this regime particle distribution functions can become strongly non-Maxwellian, and fully kinetic treatment is required. Some advanced aspects of collisionless magnetic reconnection are investigated in the present thesis. Two-dimensional numerical simulations were run on the KU Leuven supercomputing cluster VIC3 and the Pleiades supercomputer (NASA) using up to 2048 cores. Analysis of the particle trajectories near the X-line of the antiparallel magnetic reconnection is performed (Chapter 3) and a simple expression for the laminar collisionless dissipation is presented (Chapters 3 and 4). Next we focus on the separatrices of magnetic reconnection (Chapter 5). Fast electron beam is formed by the parallel electric field. The jet is unstable to the Buneman and/or electron two-stream mode. The stability properties are studied using special high-resolution PIC runs, which take the separatrix layer profile as as initial condition. A new instability of the separatrix electron jet is found. The mode can disrupt the separatrix surface into a chain of electron beams, the effect not really resolved by the two-dimensional simulations. Extension to the fully three-dimensional case is among the priorities of our future research. It will be interesting to investigate the interplay between the laminar and turbulent dissipation mechanisms, as well as the stability properties of the separatrix flow.