This is a small tool designed to take SDF files of magnetic fields produced with lare3d and integrate certain quanities along the magnetic field lines.
The lines are calculated using the tool Mayavi and the given quantity integrated along with a simple midpoint rule integration. This produces a grid of integrated values.
Currently the quantities available are:
- Parallel electric field -
$(\vec{j} \cdot \vec{B})/|\vec{B}|$ - Twist -
$(\vec{j} \cdot \vec{B})/|\vec{B}|^2$ - "Connectivity" - a field line is labeled with a certain connectivity if it starts and ends in specifically defined boundary zones. This is very situation dependent.
This tool is purely provided for interest/inspiration and is unlikely to be of direct use in other research. If you would like to improve it, please do submit a pull request!
Running python twist_calc.py will display a brief help. Descriptions of some options are below.
grid_width sets the width of the square grid of seed points.
map_point attempts to remap the grid of integrated quanities back to the given point. This often doesn't work very well.
integration_variable sets which variable should be integrated
starting_z sets the z-location of the initial plane of seed points.
The following example will integrate the parallel electric field along field lines derived from the field in input.sdf producing a grid of 700x700 outputs in output.npy:
python twist_calc.py --integration_variable parallel_electric_field --input input.sdf --output output.npy --grid_width 700
- Will not work with the default staggered grid magnetic field output from lare. The field must be centred.
- Grid of field line seed points is always normal to
$z$ and square. This can be changed by editing the script.
Also included is a very basic visualisation tool for quick plotting. For production plots, I recommend importing the outputs into python and plotting them properly.