Introduction
ARC7 is a 2.5D time dependent MHD model of the Solar Corona.
The code is designed for parametric style studies of transients in
the solar corona.
Physics Included
The code solves the ideal MHD equations in spherical coordinates with the
assumption of azimuthal symmetry. The solution variables are functions
or radius and latitude. The code solves for all 3 components of momentum
density and magnetic field, hence the code is 2.5D.
The energy equation includes field aligned thermal conduction, optically thin
radiative losses and an explicit heating function. The radial momentum
equation includes an explicit acceleration force to enable tuning of the
solar wind solution.
Numerical Methods
The code uses an FCT algorithm to advance the MHD equations, and a
sub-cycling GMRES implict solver to integrate the anisotropic thermal conduction term.
The code uses a spherical grid which can extend to 1AU.
Boundary Conditions
The code applies symmetry conditions at the north and south poles. At the
models inner radius the flow is assumed to be subsonic. i
The boundary conditions at the inner radial boundary are based on the assumption
that the flow is field-aligned and that the hydrodynamic boundary values can
be set using characteristic analysis for a quasi-1D flow aligned with
the field.
The boundary temperature is kept fixed (with a default value of 500,000K). The plasma velocity is computed by solving the characteristic equation for the v-c outgoing pressure wave. When the plasma flow is outward at this boundary the boundary mass density is set using the REB approach pioneered by Withbroe. When the boundary plasma flow is inward the density is computed by solving the entropy characteristic.
At the outer radial boundary the solution is assumed to be supersonic and super-alfvenic.
User Interface
The code has a simple intuitive GUI designed to assist users in
configuring the code for the calculations they wish to run.
Visualization Tools
The tarball include some basic graphics utilities written in Idl.
Documentation
The tarball includes a README file with a simple list of installation
instructions. It also described how to visualize run output. The GUI
is still under development, and its documentation will be added shortly.
Portability
The code is in parallelized Fortran 95 using MPI. It has been tested
on numerous platforms. The tarball includes sample Makefile for user assistance
with compilation, including settings for the Nag, Intel and Gfortran
compilers.
Download
arc7.tar
References
Allred,J. and MacNeice,P.J., "An MHD Code for the Study of Magnetic Structures
in the Solar Wind", 2009, in prep.
Contacts