Re-projecting from CAR to CEA

The pfsspy solver takes a cylindrical-equal-area (CEA) projected magnetic field map as input, which is equally spaced in sin(latitude). Some synoptic field maps are equally spaced in latitude however, which is a plate carée (CAR) projection.

This example shows how to use the pfsspy.utils.car_to_cea function to reproject a CAR projection to a CEA projection that pfsspy can take as input.

from pfsspy import sample_data
from pfsspy import utils
import matplotlib.pyplot as plt

Load a sample ADAPT map, which has a CAR projection

adapt_maps = utils.load_adapt(sample_data.get_adapt_map())
adapt_map_car = adapt_maps[0]

Out:

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Re-project into a CEA projection

adapt_map_cea = utils.car_to_cea(adapt_map_car)

Out:

/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.1/lib/python3.7/site-packages/sunpy/map/mapbase.py:838: SunpyUserWarning: Missing metadata for observer: assuming Earth-based observer.

  warnings.warn(warning_message, SunpyUserWarning)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.1/lib/python3.7/site-packages/sunpy/map/mapbase.py:838: SunpyUserWarning: Missing metadata for observer: assuming Earth-based observer.

  warnings.warn(warning_message, SunpyUserWarning)

Plot the original map and the reprojected map

plt.figure()
adapt_map_car.plot()
plt.figure()
adapt_map_cea.plot()

plt.show()

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Out:

/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.1/lib/python3.7/site-packages/sunpy/map/mapbase.py:838: SunpyUserWarning: Missing metadata for observer: assuming Earth-based observer.

  warnings.warn(warning_message, SunpyUserWarning)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.1/lib/python3.7/site-packages/astropy/wcs/wcs.py:687: FITSFixedWarning: 'datfix' made the change 'Set DATE-REF to '1858-11-17' from MJD-REF'.
  FITSFixedWarning)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.1/lib/python3.7/site-packages/sunpy/map/mapbase.py:838: SunpyUserWarning: Missing metadata for observer: assuming Earth-based observer.

  warnings.warn(warning_message, SunpyUserWarning)