TY - JOUR
T1 - Particle dynamics in a non-flaring solar active region model
AU - Threlfall, J.
AU - Bourdin, Ph A.
AU - Neukirch, T.
AU - Parnell, C. E.
N1 - Funding Information:
The authors gratefully acknowledge the support of the UK Science and Technology Facilities Council [Consolidated Grant ST/K000950/1]. The research leading to these results has received funding from the European Commission’s Seventh Framework Programme FP7 under the grant agreement SHOCK (project number 284515). This work was supported by the International Max-Planck Research School (IMPRS) on Solar System Physics. The results of this research have been achieved using the PRACE Research Infrastructure resource Curie based in France at TGCC, as well as JuRoPA hosted by the Jülich Supercomputing Centre in Germany. Preparatory work has been executed at the Kiepenheuer-Institut für Sonnenphysik in Freiburg, as well as on the bwGRiD facility located at the Universität Freiburg, Germany. We thank Suguru Kamio for his help finding active region observations. Hinode is a Japanese mission developed, launched, and operated by ISAS/JAXA, in partnership with NAOJ, NASA, and STFC (UK). Additional operational support is provided by ESA and NSC (Norway).
Publisher Copyright:
© 2016 ESO.
Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.
PY - 2016/3/1
Y1 - 2016/3/1
N2 - 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.
AB - 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.
U2 - 10.1051/0004-6361/201526657
DO - 10.1051/0004-6361/201526657
M3 - Article
AN - SCOPUS:84958559290
VL - 587
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 0004-6361
M1 - A4
ER -