make_diagram.py

import numpy as np
import matplotlib.pyplot as plt

from astropy import units as u
from astropy.coordinates import SkyCoord

import sunpy.map


pixels = 300 * u.pix
sun_radius = (980 * u.arcsec).to(u.deg)
fov = sun_radius * 3
delta = fov / pixels

sky = np.zeros((int(pixels.value), int(pixels.value)))
mymeta = {'naxis1': pixels.value, 'naxis2': pixels.value,
          'cdelt1': delta.value, 'cdelt2': delta.value,
          'crpix1': 150.5, 'crpix2': 150.5,
          'crval1': 0, 'crval2': 0,
          'ctype1': 'HPLN-TAN', 'ctype2': 'HPLT-TAN',
          'cunit1': 'arcsec', 'cunit2': 'arcsec',
          'rsun_obs': sun_radius.value, 'dsun_obs': (1 * u.au).to(u.m).value}

mymap = sunpy.map.Map(sky, mymeta)

fig = plt.figure()
ax = plt.subplot(projection=mymap)

mymap.plot(axes=ax, vmin=-100, vmax=0)

mymap.draw_grid(axes=ax, color='black')
mymap.draw_limb(axes=ax, color='black')
ax.coords.grid(color='black', alpha=0.5, linestyle='solid')

#text
ax.text(sun_radius.value, 0, 'West limb', transform=ax.transAxes)
ax.text(-sun_radius.value, 0, 'East limb', transform=ax.transAxes, horizontalalignment='right')
ax.text(0, sun_radius.value, 'North pole')
ax.text(0, -sun_radius.value, 'South pole')

#arrows
ax.arrow(0, 0, 0.25 * sun_radius.value, 0, head_width=0.05, head_length=0.01, fc='k', ec='k')
ax.arrow(0, 0, 0, 0.25 * sun_radius.value, head_width=0.05, head_length=0.01, fc='k', ec='k')
ax.text(0, 0.12 * sun_radius.value, 'x', verticalalignment='top')
ax.text(0.12 * sun_radius.value, 0, 'y', horizontalalignment='right')


ax.set_title('')
fig.show()