Exporting COCONUT Field Lines to JHelioviewer

coconut_tools.visualization_3d.coconut_to_jhv converts a COCONUT/COOLFluid .vtu or .CFmesh file into a SunJSON file containing magnetic-field lines for JHelioviewer.

The script:

  1. Reads the COCONUT mesh and its Cartesian magnetic-field components.

  2. Traces magnetic-field streamlines from a spherical seed grid.

  3. Optionally creates a PyVista preview.

  4. Exports the field lines in SunJSON coordinates: [radius, Carrington longitude, Carrington latitude].

The mesh coordinates are assumed to be in solar radii, with the x-y plane as the solar equatorial plane and z pointing toward solar north.

Command-line use

Basic export:

python -m coconut_tools.visualization_3d.coconut_to_jhv corona.CFmesh fieldlines.json

Export with a screenshot and progress bars:

python -m coconut_tools.visualization_3d.coconut_to_jhv corona.CFmesh fieldlines.json --screenshot preview.png --progress

Color the field lines by the radial magnetic field, Br:

python -m coconut_tools.visualization_3d.coconut_to_jhv corona.CFmesh fieldlines.json \
  --screenshot preview.png \
  --progress \
  --color-by br

The screenshot and SunJSON export use the same blue-white-red colormap. Its limits are symmetric and set to [-2 std(Br), +2 std(Br)] using the interpolated field-line values in gauss.

Longitude orientation can be adjusted when required:

python -m coconut_tools.visualization_3d.coconut_to_jhv input.vtu fieldlines.json \
  --longitude-offset-deg 180 \
  --flip-longitude

The default seed count is 200. Use --n-seed-points to change it.

Python use

from coconut_tools.visualization_3d.coconut_to_jhv import export_to_jhv_json

export_to_jhv_json(
    input_file="corona.CFmesh",
    output_json="fieldlines.json",
    screenshot="preview.png",
    use_tqdm=True,
    color_by="br",
)

Open in JHelioviewer

  1. Start JHelioviewer.

  2. Drag and drop fieldlines.json into the JHelioviewer window.

  3. In the layer list, enable the checkbox for the Connection layer.

The exported magnetic-field lines should then appear in the 3D view.

Colored COCONUT field lines in JHelioviewer