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"""
===========================================
Downloading and plotting an HMI magnetogram
===========================================
This example shows how to download a HMI magnetogram data with Fido and make a plot.
"""
import matplotlib.pyplot as plt
import sunpy.map
from sunpy.net import Fido
from sunpy.net import attrs as a
###############################################################################
# To download the required data, we use `sunpy.net.Fido`, a downloader client,
# to query the Virtual Solar Observatory to acquire HMI data.
result = Fido.search(a.Time('2020/01/20 00:00:00', '2020/01/20 00:01:00'),
a.Instrument.hmi, a.Physobs.los_magnetic_field)
###############################################################################
# Now we can see what results we obtained from our search.
print(result)
###############################################################################
# The following shows how to download the results. If we
# don't provide a path it will download the file into the sunpy data directory.
# The output provides the path of the downloaded files.
downloaded_file = Fido.fetch(result)
print(downloaded_file)
###############################################################################
# Now load it into a map and plot it.
# We see that solar North is pointed down instead of up in this image, which is
# indicated by the coordinates (that range from positive to negative, rather
# than negative to positive).
hmi_map = sunpy.map.Map(downloaded_file[0])
fig = plt.figure()
hmi_map.plot()
plt.show()
###############################################################################
# Now rotate the image such that solar North is pointed up.
# We have to do this because the HMI instrument is mounted upside-down
# relative to the AIA instrument on the SDO satellite, which means most
# of the images are taken with solar North pointed up.
# The roll angle of the instrument is reported in the FITS header
# keyword `CROTA2` (see Figure 17 of
# `Couvidat et al. (2016) <https://dx.doi.org/10.1007/s11207-016-0957-3>`_,
# which states that "the nominal CROTA2 for HMI is ≈179.93").
#
# The order keyword, below, specifies the type of interpolation;
# in this case, 3 refers to bi-cubic.
hmi_rotated = hmi_map.rotate(order=3)
hmi_rotated.plot()
plt.show()
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