Field lines with pyvista

Visualising traced field lines with pyvista.

pyvista is a Python package that provides a wrapper to the popular VTK library for 3D visualisation. Unlike Matplotlib this is “true” 3D rendering, and is much more performant in comparison.

First, load the required modules.

import astropy.units as u
import numpy as np

from psipy.data import sample_data
from psipy.model import MASOutput
from psipy.tracing import FortranTracer
from psipy.visualization.pyvista import PyvistaPlotter

Load a set of MAS output files.

mas_path = sample_data.mas_sample_data()
model = MASOutput(mas_path)

To trace field lines, start by creating a tracer. Then we create a set of seed points at which the field lines are drawn from.

tracer = FortranTracer()

nseeds = 20
r = np.ones(nseeds**2) * 40 * u.R_sun
lat = np.linspace(-45, 45, nseeds**2, endpoint=False) * u.deg
lon = np.random.rand(nseeds**2) * 360 * u.deg

# Do the tracing!
flines = tracer.trace(model, r=r, lat=lat, lon=lon)

Visualise the results

plotter = PyvistaPlotter(model)
br = model["br"]
for fline in flines:
    # Set color with polarity near the inner boundary
    color = (
        br.sample_at_coords(
            np.mod(fline.lon[1], 2 * np.pi * u.rad),
            fline.lat[1],
            fline.r[1],
        )
        > 0
    )
    color = {0: "red", 1: "blue"}[int(color)]
    plotter.add_fline(fline, color=color)

# Add a sphere at the inner boundary of the model
plotter.add_sphere(np.min(br.r_coords))
plotter.show()