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, attrs as a
To download the required data, we use
Fido, a downloader client,
to query the Joint Science Operations Center, or JSOC, where HMI data are stored.
First define the search variables, a timerange,
a data series,
keywords, and your e-mail address (to notify you when the download is complete).
See the JSOC e-mail address registration page
result = Fido.search(a.Time('2014/11/20 00:00:00', '2014/11/20 00:04:00'), a.jsoc.Series("hmi.M_720s"), a.jsoc.Keys(["T_REC, CROTA2"]), a.jsoc.Notify("[email protected]"))
Now we can see what results we obtained from our search. Notice we have two files.
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. The result can be from several data clients, so we have to index the client first and then index the file.
# Slice the first record returned by the first client. 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) 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
CROTA2 (see Figure 17 of
Couvidat et al. (2016),
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()
Total running time of the script: ( 0 minutes 0.000 seconds)