Loading an HMI synoptic map

In this example we load a synoptic map produced by the HMI team. This data is an interesting demonstration of sunpy’s Map class as it is not in the more common Helioprojective coordinate system, but in heliographic Carrington coordinates and a cylindrical equal area (CEA) projection.

import matplotlib.pyplot as plt

from astropy.utils.data import download_file

import sunpy.map

Download the file and read it into a Map.

filename = download_file(
    'http://jsoc.stanford.edu/data/hmi/synoptic/hmi.Synoptic_Mr.2191.fits', cache=True)
syn_map = sunpy.map.Map(filename)

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/checkouts/stable/examples/plotting/hmi_synoptic_maps.py", line 20, in <module>
    filename = download_file(
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/site-packages/astropy/utils/data.py", line 1393, in download_file
    raise errors[sources[0]]
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/site-packages/astropy/utils/data.py", line 1363, in download_file
    f_name = _download_file_from_source(
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/site-packages/astropy/utils/data.py", line 1167, in _download_file_from_source
    with _try_url_open(source_url, timeout=timeout, http_headers=http_headers,
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/site-packages/astropy/utils/data.py", line 1104, in _try_url_open
    return urlopener.open(req, timeout=timeout)
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/urllib/request.py", line 519, in open
    response = self._open(req, data)
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/urllib/request.py", line 536, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/urllib/request.py", line 496, in _call_chain
    result = func(*args)
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/urllib/request.py", line 1377, in http_open
    return self.do_open(http.client.HTTPConnection, req)
  File "/home/docs/checkouts/readthedocs.org/user_builds/sunpy/conda/stable/lib/python3.10/urllib/request.py", line 1351, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error timed out>

Plot the results.

fig = plt.figure(figsize=(12, 5))
ax = plt.subplot(projection=syn_map)
im = syn_map.plot(axes=ax)

ax.coords[0].set_axislabel("Carrington Longitude [deg]")
ax.coords[1].set_axislabel("Latitude [deg]")

ax.coords.grid(color='black', alpha=0.6, linestyle='dotted', linewidth=0.5)

cb = plt.colorbar(im, fraction=0.019, pad=0.1)
cb.set_label(f"Radial magnetic field [{syn_map.unit}]")

# In order to make the x-axis ticks show, the bottom y-limit has to be adjusted slightly
ax.set_ylim(bottom=0)
ax.set_title(f"{syn_map.meta['content']},\n"
             f"Carrington rotation {syn_map.meta['CAR_ROT']}")

plt.show()