The Thomson Sphere

This example demonstrates add_thompson_sphere() — a convenience method that adds the Thomson sphere for a given observer position.

The Thomson sphere is the sphere centered halfway between the Sun and the observer, with radius \(\|\mathbf{p}_ ext{obs}\|/2\). It represents the locus of points of maximum Thomson scattering efficiency along any line of sight through the corona: a photon emitted from a coronal electron contributes most strongly to an observer’s signal when that electron lies on or near this sphere.

from math import pi
from pyvisual import Plot3d

Thomson Sphere for an Equatorial Observer

Place an observer at \(r = 10\,R_\odot\) on the equatorial plane (\(\theta = \pi/2,\,\phi = 0\)). The Thomson sphere is centered at \((5\,R_\odot, 0, 0)\) with radius \(5\,R_\odot\). The observer’s position is marked with a red point for reference, and the camera is moved to a wider vantage point to show the full geometry.

observer_position = 10, pi / 2, 0

plotter = Plot3d(off_screen=True, window_size=(500, 500))
plotter.show_axes()
plotter.add_sun()
plotter.observer_position = observer_position
plotter.add_thompson_sphere(opacity=0.3, color='cyan')
plotter.add_point(*observer_position, color='red', point_size=10)
plotter.observer_position = 50, pi / 2, pi / 6
plotter.show()

Static Scene

Interactive Scene