Particle acceleration in explosive reconnection

Bart Ripperda, KU Leuven, Belgium

Magnetic reconnection is the mechanism behind many violent phenomena in the universe. We demonstrate that energy released during reconnection can lead to non-thermal particle distribution functions. We use a method in which we combine resistive magnetohydrodynamics (MHD) with relativistic test particle dynamics. Using our open-source grid-adaptive MPI-AMRVAC software, we simulate global MHD evolution combined with test particle treatments. The dynamics of particles in a non-relativistic, magnetised plasma can be approximated by the relativistic guiding centre approximation. This method allows particles to reach relativistic energies, neglecting the gyromotion of the particles. This approach is used to evaluate particle acceleration in explosive reconnection, triggered by current-driven instabilities in 2.5D and 3D scenarios. Non-thermal particle distributions are formed in (up to tearing unstable) current sheets, mainly due to resistive electric fields. We analyse acceleration mechanisms and energetics of particles in proton-electron plasmas, which is relevant for particle acceleration in solar flares and in other, more exotic astrophysical phenomena, like black hole flares, magnetar magnetospheres and pulsar wind nebulae.