Particle dynamics in a non-flaring solar active region model
Abstract
Aims: The aim of this work is to investigate and characterise particle behaviour in an (observationally-driven) 3D magnetohydrodynamic (MHD) model of the solar atmosphere above a slowly evolving, non-flaring active region.
Methods: We use a relativistic guiding-centre particle code to investigate the behaviour of selected particle orbits, distributed throughout a single snapshot of the 3D MHD simulation.
Results: Two distinct particle acceleration behaviours are recovered, which affect both electrons and protons: (I) direct acceleration along field lines and (II) tangential drifting of guiding centres with respect to local magnetic field. However, up to 40% of all particles actually experience a form of (high energy) particle trap, because of changes in the direction of the electric field and unrelated to the strength of the magnetic field; such particles are included in the first category. Additionally, category (I) electron and proton orbits undergo surprisingly strong acceleration to non-thermal energies (≲42 MeV), because of the strength and extent of super-Dreicer electric fields created by the MHD simulation. Reducing the electric field strength of the MHD model does not significantly affect the efficiency of the (electric field-based) trapping mechanism, but does reduce the peak energies gained by orbits. We discuss the implications for future experiments, which aim to simulate non-flaring active region heating and reconnection.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 2016
- DOI:
- 10.1051/0004-6361/201526657
- arXiv:
- arXiv:1510.04211
- Bibcode:
- 2016A&A...587A...4T
- Keywords:
-
- plasmas;
- Sun: corona;
- Sun: magnetic fields;
- Sun: activity;
- acceleration of particles;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- submitted to A&