2005/09/23 by K. Arzner, Kaspar Arzner, Bernard Knaepen +4 · 3 citations
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Geomagnetism and Paleomagnetism Studies #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.1086/498341
published as Astrophys.J.637:322-332,2006 · accepted for publication in ApJ
arxiv created 2005/09/23 · openalex publication_date 2006/01/12 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We investigate the influence of coherent structures on particle acceleration in the strongly turbulent solar corona. By randomizing the Fourier phases of a pseudospectral simulation of isotropic magnetohydrodynamic (MHD) turbulence (Re ~ 300) and tracing collisionless test protons in both the exact-MHD and phase-randomized fields, it is found that the phase correlations enhance the acceleration efficiency during the first adiabatic stage of the acceleration process. The underlying physical mechanism is identified as the dynamical MHD alignment of the magnetic field with the electric current, which favors parallel (resistive) electric fields responsible for initial injection. Conversely, the alignment of the magnetic field with the bulk velocity weakens the acceleration by convective electric fields - u × b at a nonadiabatic stage of the acceleration process. We point out that nonphysical parallel electric fields in random-phase turbulence proxies lead to artificial acceleration and that the dynamical MHD alignment can be taken into account on the level of the joint two-point function of the magnetic and electric fields and is therefore amenable to Fokker-Planck descriptions of stochastic acceleration.