![]() This is the most complete method, but as mentioned, it has to resolve the microscopic scales of the plasma, demanding extreme computational cost. 2015 for non-relativistic plasmas) treat both electrons and ions as particles, and iteratively move these particles and update the electromagnetic fields accordingly. ![]() 2015 for relativistic plasmas and Markidis & Lapenta 2011 Li et al. Fully kinetic particle-in-cell (PIC) codes (e.g. There are currently many efforts to overcome this issue and to bridge the gap between the two approaches. That, however, does not give any information on particle acceleration within reconnection regions, nor does it include the effect of accelerated particles on the global fields. However, reconnection can be studied in the MHD context by a parametrization approximating particle interactions on scales below the characteristic MHD length-scales through viscosity and resistivity. During reconnection, this approximation breaks down. The macroscopic approximation describes the time-dependent evolution of magnetic fields, bulk velocity fields and density of the plasma. On the fundamental particle level, the energy released by magnetic reconnection goes into the kinetic energy of individual particles however, investigating how instabilities lead to large-scale dynamics in astrophysical systems is traditionally done with a magnetohydrodynamics (MHD) approach. One of the most important processes exhibiting these distinctive differences, which are tightly coupled on the different scales, is magnetic reconnection. The complexity of modelling such a system comes from the coupling of relatively slow macroscopic processes and faster processes on the particle scale. The obtained results hold as a proof-of-principle for test particle approaches in MHD simulations, relevant to explore less idealized scenarios like solar flares and more exotic astrophysical phenomena, like black hole flares, magnetar magnetospheres and pulsar wind nebulae.Īcceleration of particles, instabilities, magnetic reconnection, MHD, methods: numerical 1 INTRODUCTIONĪstrophysical plasmas are systems in which physical phenomena are coupled from macroscopic to microscopic scales in space and time. We discuss the MHD of an additional kink instability in 3D setups and the expected effects on energy distributions. Solutions to these numerical artefacts are proposed for both 2.5D setups and future 3D work. Due to large resistive electric fields and indefinite acceleration of particles in the infinitely long current channels, hard energy spectra are found in 2.5D configurations. We quantify energy distributions, acceleration mechanisms, relativistic corrections to the particle equations of motion and effects of resistivity in magnetically dominated proton–electron plasmas. ![]() We explore under which plasma-β conditions the fastest reconnection occurs in 2.5D scenarios, and in these settings, test particles are evolved. Using the recently developed particle module of our open-source grid-adaptive mpi-amrvac software, we simulate MHD evolution combined with test particle treatments in MHD snapshots. The current channels undergo a rotation and separation on Alfvénic time-scales, forming secondary islands and (up to tearing unstable) current sheets in which non-thermal energy distributions are expected to develop. We propose a system with two parallel, repelling current channels in an initially force-free equilibrium, as a simplified representation of flux ropes in a stellar magnetosphere. Magnetic reconnection and non-thermal particle distributions associated with current-driven instabilities are investigated by means of resistive magnetohydrodynamics (MHD) simulations combined with relativistic test particle methods.
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