HMI PFSS solutions

Calculating a PFSS solution from a HMI synoptic map.

This example shows how to calcualte a PFSS solution from a HMI synoptic map. There are a couple of important things that this example shows:

• HMI maps have non-standard metadata, so this needs to be fixed

• HMI synoptic maps are very big (1440 x 3600), so need to be downsampled in order to calculate the PFSS solution in a reasonable time.

First import the required modules

import astropy.units as u
import matplotlib.pyplot as plt
from sunpy.net import Fido, attrs as a
import sunpy.map
import pfsspy
import pfsspy.utils

Set up the search.

Note that for SunPy versions earlier than 2.0, a time attribute is needed to do the search, even if (in this case) it isn’t used, as the synoptic maps are labelled by Carrington rotation number instead of time

time = a.Time('2010/01/01', '2010/01/01')
series = a.jsoc.Series('hmi.synoptic_mr_polfil_720s')
crot = a.jsoc.PrimeKey('CAR_ROT', 2210)

Do the search.

If you use this code, please replace this email address with your own one, registered here: http://jsoc.stanford.edu/ajax/register_email.html

result = Fido.search(time, series, crot, a.jsoc.Notify("jsoc@cadair.com"))
files = Fido.fetch(result)

Out:

Export request pending. [id=JSOC_20210131_501_X_IN, status=2]
Waiting for 0 seconds...
1 URLs found for download. Full request totalling 4MB

Files Downloaded:   0%|          | 0/1 [00:00<?, ?file/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   0%|          | 0.00/4.26M [00:00<?, ?B/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   0%|          | 100/4.26M [00:00<1:33:28, 759B/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   0%|          | 19.4k/4.26M [00:00<00:48, 87.8kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   1%|1         | 50.9k/4.26M [00:00<00:26, 158kB/s] 

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   2%|2         | 95.1k/4.26M [00:00<00:18, 231kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   4%|3         | 151k/4.26M [00:00<00:13, 303kB/s] 

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   5%|5         | 224k/4.26M [00:00<00:10, 392kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:   7%|7         | 319k/4.26M [00:00<00:07, 507kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  10%|#         | 431k/4.26M [00:01<00:06, 621kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  13%|#3        | 569k/4.26M [00:01<00:04, 762kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  17%|#7        | 732k/4.26M [00:01<00:03, 916kB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  21%|##1       | 899k/4.26M [00:01<00:03, 1.04MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  26%|##6       | 1.11M/4.26M [00:01<00:02, 1.22MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  31%|###1      | 1.33M/4.26M [00:01<00:02, 1.38MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  37%|###6      | 1.57M/4.26M [00:01<00:01, 1.52MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  44%|####3     | 1.87M/4.26M [00:01<00:01, 1.76MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  50%|#####     | 2.14M/4.26M [00:02<00:01, 1.87MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  57%|#####6    | 2.41M/4.26M [00:02<00:00, 1.88MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  63%|######2   | 2.67M/4.26M [00:02<00:00, 2.05MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  69%|######8   | 2.93M/4.26M [00:02<00:00, 2.15MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  76%|#######6  | 3.25M/4.26M [00:02<00:00, 2.36MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  85%|########4 | 3.62M/4.26M [00:02<00:00, 2.67MB/s]

hmi.synoptic_mr_polfil_720s.2210.Mr_polfil.fits:  94%|#########3| 4.00M/4.26M [00:02<00:00, 2.99MB/s]
Files Downloaded: 100%|##########| 1/1 [00:02<00:00,  2.96s/file]
Files Downloaded: 100%|##########| 1/1 [00:02<00:00,  2.96s/file]


                                                                                                     

Read in a file. This will read in the first file downloaded to a sunpy Map object. Note that HMI maps have several bits of metadata that do not comply to the FITS standard, so we need to fix them first.

hmi_map = sunpy.map.Map(files[0])
pfsspy.utils.fix_hmi_meta(hmi_map)
print('Data shape: ', hmi_map.data.shape)

Out:

Data shape:  (1440, 3600)

Since this map is far to big to calculate a PFSS solution quickly, lets resample it down to a smaller size.

hmi_map = hmi_map.resample([360, 180] * u.pix)
print('New shape: ', hmi_map.data.shape)

Out:

/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:484: FITSFixedWarning: CRDER1 = 'nan '
a floating-point value was expected.
  colsel=colsel, hdulist=fobj)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:484: FITSFixedWarning: CRDER2 = 'nan '
a floating-point value was expected.
  colsel=colsel, hdulist=fobj)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:709: FITSFixedWarning: 'unitfix' made the change 'Changed units:
  'degree' -> 'deg'.
  FITSFixedWarning)
New shape:  (180, 360)

Now calculate the PFSS solution

nrho = 35
rss = 2.5
input = pfsspy.Input(hmi_map, nrho, rss)
output = pfsspy.pfss(input)

Out:

/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/pfsspy/input.py:40: UserWarning: Input data has a non-zero mean. pfsspy will ignore this non-zero monopole term when calculating the PFSS solution.
  warnings.warn('Input data has a non-zero mean. '

Using the Output object we can plot the source surface field, and the polarity inversion line.

ss_br = output.source_surface_br
# Create the figure and axes
fig = plt.figure()
ax = plt.subplot(projection=ss_br)

# Plot the source surface map
ss_br.plot()
# Plot the polarity inversion line
ax.plot_coord(output.source_surface_pils[0])
# Plot formatting
plt.colorbar()
ax.set_title('Source surface magnetic field')

plt.show()

Out:

/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:484: FITSFixedWarning: CRDER1 = 'nan '
a floating-point value was expected.
  colsel=colsel, hdulist=fobj)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:484: FITSFixedWarning: CRDER2 = 'nan '
a floating-point value was expected.
  colsel=colsel, hdulist=fobj)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:709: FITSFixedWarning: 'unitfix' made the change 'Changed units:
  'degree' -> 'deg'.
  FITSFixedWarning)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/visualization/wcsaxes/core.py:211: MatplotlibDeprecationWarning: Passing parameters norm and vmin/vmax simultaneously is deprecated since 3.3 and will become an error two minor releases later. Please pass vmin/vmax directly to the norm when creating it.
  return super().imshow(X, *args, origin=origin, **kwargs)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:484: FITSFixedWarning: CRDER1 = 'nan '
a floating-point value was expected.
  colsel=colsel, hdulist=fobj)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:484: FITSFixedWarning: CRDER2 = 'nan '
a floating-point value was expected.
  colsel=colsel, hdulist=fobj)
/home/docs/checkouts/readthedocs.org/user_builds/pfsspy/envs/0.6.6/lib/python3.7/site-packages/astropy/wcs/wcs.py:709: FITSFixedWarning: 'unitfix' made the change 'Changed units:
  'degree' -> 'deg'.
  FITSFixedWarning)