Program to extrapolate linear force-free fields in 3D Cartesian coordinates, based on exact Green function method (Chiu & Hilton 1977 ApJ 212,873). More...

Functions/Subroutines
subroutine	init_b_fff_data (magnetogramname, qLunit, qBunit)

subroutine	calc_lin_fff (ixIL, ixOL, Bf, x, alpha, zshift, idir)

subroutine	get_potential_field_potential (ixIL, ixOL, potential, x, zshift)

Variables
integer, save	nx1

integer, save	nx2

double precision, save	bzmax

double precision, save	darea

double precision, dimension(:,:), allocatable, save	bz0

double precision, dimension(:), allocatable, save	xa1

double precision, dimension(:), allocatable, save	xa2

Detailed Description

Program to extrapolate linear force-free fields in 3D Cartesian coordinates, based on exact Green function method (Chiu & Hilton 1977 ApJ 212,873).

Usage: 1 In the subroutine usr_set_parameters of mod_usr.t: To extrapolate a linear force free field from a observed magnetogram prepared in a data file, e.g., 'hmiM720sxxxx.dat' replace call init_bc_fff_data('hmiM720sxxxx.dat',unit_length,unit_magneticfield) 'hmiM720sxxxx.dat' must be a binary file containing nx1,nx2,xc1,xc2,dxm1, dxm2, Bz0(nx1,nx2). Integers nx1 and nx2 give the resolution of the uniform-grid magentogram. Others are double-precision floats. xc1 and xc2 are coordinates of the central point of the magnetogram. dxm1 and dxm2 are the cell sizes for each direction, Bz0 is the vertical conponent of magetic field on the solar surface from observations. 2 In the subroutine usr_init_one_grid of mod_usr.t, add lines like:

double precision :: Bf(ixG^S,1:ndir), alpha, zshift

alpha=0.d0 ! potential field !alpha=0.08d0 ! non-potential linear force-free field zshift=0.05d0 ! lift your box zshift heigher to the bottom magnetogram call calc_lin_fff(ixG^L,ix^L,Bf,x,alpha,zshift)

3 Notice that the resolution of input magnetogram must be better than the best resolution of your AMR grid to have a good behavior close to the bottom layer

Function/Subroutine Documentation

◆ calc_lin_fff()

subroutine mod_lfff::calc_lin_fff	(	integer, intent(in)	ixI,
		integer, intent(in)	L,
		integer, intent(in)	ixO,
			L,
		double precision, dimension(ixi^s,1:ndir), intent(inout)	Bf,
		double precision, dimension(ixi^s,1:ndim), intent(in)	x,
		double precision, intent(in)	alpha,
		double precision, intent(in)	zshift,
		integer, intent(in), optional	idir
	)

Definition at line 100 of file mod_lfff.t.

◆ get_potential_field_potential()

subroutine mod_lfff::get_potential_field_potential	(	integer, intent(in)	ixI,
		integer, intent(in)	L,
		integer, intent(in)	ixO,
			L,
		double precision, dimension(ixi^s), intent(inout)	potential,
		double precision, dimension(ixi^s,1:ndim), intent(in)	x,
		double precision, intent(in)	zshift
	)

Definition at line 168 of file mod_lfff.t.

◆ init_b_fff_data()

subroutine mod_lfff::init_b_fff_data	(	character(len=*), intent(in)	magnetogramname,
		double precision, intent(in)	qLunit,
		double precision, intent(in)	qBunit
	)

Definition at line 37 of file mod_lfff.t.

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Variable Documentation

◆ bz0

double precision, dimension(:,:), allocatable, save mod_lfff::bz0

Definition at line 32 of file mod_lfff.t.

◆ bzmax

double precision, save mod_lfff::bzmax

Definition at line 31 of file mod_lfff.t.

◆ darea

double precision, save mod_lfff::darea

Definition at line 31 of file mod_lfff.t.

◆ nx1

integer, save mod_lfff::nx1

Definition at line 30 of file mod_lfff.t.

◆ nx2

integer, save mod_lfff::nx2

Definition at line 30 of file mod_lfff.t.

◆ xa1

double precision, dimension(:), allocatable, save mod_lfff::xa1

Definition at line 33 of file mod_lfff.t.

◆ xa2

double precision, dimension(:), allocatable, save mod_lfff::xa2