An Ab Initio Approach to the Solar Coronal Heating Problem

Abstract

We present an ab initio approach to the solar coronal heating problem by modelling a small part of the solar corona in a computational box using a 3D MHD code including realistic physics. The observed solar granular velocity pattern and its amplitude and vorticity power spectra, as reproduced by a weighted Voronoi tessellation method, are used as a boundary condition that generates a Poynting flux in the presence of a magnetic field. The initial magnetic field is a potential extrapolation of a SOHO/MDI high resolution magnetogram, and a standard stratified atmosphere is used as a thermal initial condition. Except for the chromospheric temperature structure, which is kept fixed, the initial conditions are quickly forgotten because the included Spitzer conductivity and radiative cooling function have typical timescales much shorter than the time span of the simulation. After a short initial start up period, the magnetic field is able to dissipate 3 − 4 × 10 6 ergscm 2 s 1 in a highly intermittent corona, maintaining an average temperature of ∼ 10 6 K, at coronal density values for which emulated images of the Transition Region And Coronal Explorer(TRACE) 171 and 195 u pass bands reproduce observed photon count rates. Subject headings: Sun: corona – Sun: magnetic fields – MHD