Using Exportdata and Hg_patch to track Sunspots

Some background: The HMI and AIA instruments on the SDO mission operate the JSOC-Science Data Processing at Stanford University. In addition to primary HMI and AIA observable datasets, higher level HMI data products can also be accessed via the JSOC_exportdata page.
The available HMI data includes the Standard "HMI Observables" in 45s and 720s cadence(the frequency at which the data are taken). These are:

• Line of Sight Magnetograms (series names:hmi.M_45s, hmi.M_720s)
• Continuum Intensity: (series names: hmi.Ic_45s, hmi.Ic_720s)
• Continuum Intensity: with no Limb Darkening:( series names: hmi.Ic_noLimbDark_720s, hmi.Ic_noLimbDark_720s_nrt)
• Doppler Velocity: (series names: hmi.V_45s, hmi.V_720s )
• Line Width: (series names: hmi.Lw_45s, hmi.Lw_720s)
• Line Depth: (series names: hmi.Ld_45s, hmi.Ld_720s)

Note:" hmi.Ic_noLimbDark_720s " refers to continuum data with limb darkening removed. Limb darkening refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image. These data are available at a cadence of 720s, and 720s_nrt. The "nrt" or Near Real Time data are data that need to undergo further processing but are still fairly reliable.

AIA data available:

• AIA level 1 data: (series name:aia.lev1 .This includes all lev 1 data)
• AIA EUV(Extreme Ultraviolet) data at 12s cadence at wavelengths 94,131,171,193, 211,304 and 335 Angstrom: (series name: aia.lev1_euv_12s )
• AIA UV(Ultraviolet) data at 24s cadence at wavelengths 1600 and 1700 Angs: (series name: aia.lev1_uv_24s )
• AIA Visible light data at 24s cadence at wavelengths 4500 Angs: (series name: aia.lev1_vis_1h )

Data is stored in "series" and you need to use the correct format to access it. The HMI data series include the series name followed by the data and time: for ex:
hmi.M_45s[2011.01.01_01:30:00_TAI/30m] refers to the LOS Magnetograms on the date 2011/01/01 at time 01:01:30_TAI for an interval of the next 30 min.
Similarly, hmi.Ic_45s[2011.01.01_01:30_TAI-2011.01.01_02:00_TAI] This query requests all HMI continuum data for January 1, 2011 between 01:30 and 02:00 TAI.

For AIA data however, because the cadences are so high, we need to be more specific: For eg:
aia.lev1[2011.01.01_01:30/30m]: This query requests all AIA image records for January 1, 2011 for the half hour starting at 01:30. It will return 1200 records!! (one image in each of 8 wavelength channels every 12 seconds).
However,if we use aia.lev1[2011.01.01_01:30/30m][? WAVELNTH=171 ?]: This query now subselects the data from the above query to include only those image records for which the WAVELNTH keyword equals 171 (i.e., images from the 171Å channel of AIA). It will return 150 records (one image every 12 seconds).
aia.lev1[2011.01.01_01:30/30m][? WAVELNTH=171 or WAVELNTH=304 ?]: This query returns those image records for which the WAVELNTH keyword equals either 171 or 304. It returns 300 records.

Exporting data

See tutorial at http://soi.stanford.edu/~mbobra/JSOC_Tutorial/JSOC_Tutorial.mov

However; for the purposes of tracking sunspots: knowing the name of the dataseries we want, and National Oceanic and Atmospheric Administration (NOAA) Active Region:NOAA AR # numbers may be sufficient. A good source to find the active region number on aprticular day is Solar monitor page at http://www.solarmonitor.org/ or the Helio Event Knowledge base (HEK) at http://www.lmsal.com/hek. Once you know the active region number,you are ready to get your data.

Example 1: checking to see if the data are there

• Go to the exportdata page at: http://jsoc.stanford.edu/ajax/exportdata.html. Type in your series name and time duration in the RecordSet box .Type in :"hmi.M_45s[2011.12.12_03:10:00/30m]" If you click "Recount" ; it will show you how many records(40) are there in the series you selected.

Example 2: HMI data using NOAA regions

1. This time go down to the "Method" box, select url.
2. In the now visible "Processing" select box, select hg_patch
3. Click through the two popups that appear
4. In the drop-down list for "Series" pick hmi_Ic_noLimbDark_720s
5. NOAA region box, enter your favorite region - more than 5 days old for this data, Try for this test, 1410,
6. For a first try, enter 24h in the cadence box.(can be a multiple of the series cadence)
7. Then enter e.g. 500 in both width and height of the box sizes.
8. In the protocol box check jpeg images.
9. Ignore the colortable etc. They are not quite functional yet.
10. Enter your email address in the notify box and click submit.
11. After about 10-12 seconds, move down to the darker blue panel and click on submit status request. Its a good idea to wait as sometimes the requests havent gotten through and its messes up things.
12. Click submit again to determine the status of your request. Your image should soon be ready. Click on the url that you are pointed to.
13. Click on the jpeg image. This one shows the spot a bit off center, so go back up to the light bluepanel, the X and Y boxes are locations in solar degrees from disk center (well central meridian and equator) so to center the spot a bit change X from 0 to 4
14. GO back up to the Record Count line, click recount button to let you submit the same request again. Then Submit export request again, and get status until you get the result.
15. Note: for the Ic_noLimbDark series; you need to use the NOAA AR nos as that series has only been created for Active Regions. For the other HMI series you could use NOAA regions or put in your T-start and T-stop. See examples below.

Example 2: HMI data using T_start and T_stop.

1. This example is udeful if you know the coordinates on the sun of the area you want to look at.
2. Reset the page. Always clear the earlier request. If you know the series you are planning to look at,proceed as above till #4. (In this case we know we would like to pick and an hmi series). Then from the drop box pick another HMI series , say hmi.M_720s
3. put in a T_start time in the correct format: 2011.12.12_12:00:00_TAI and T_STOP: 2011.12.12_13:00:00_TAI
4. In the Cadence put in 720s.
5. For T_REF, you can put in the starting time
6. Then enter e.g. 500 in both width and height of the box sizes.
7. put in a value for X and Y say, 1200 and 1500.(theses are CCD pixels )
8. In the protocol box check MP4.
9. Again Ignore the colortable etc. They are not quite functional yet.
10. Enter your email address in the notify box and click submit.
11. After about 10-12 seconds, move down to the darker blue panel and click on submit status request. Its a good idea to wait as sometimes the requests havent gotten through and its messes up things.
12. Click submit again to determine the status of your request. Your images and movie should soon be ready. Click on the url that you are pointed to.
13. Note : If you have put in a NOAA number, then it overrides the "cadence" value you may have put, and assumes the basic data cadence.

Example 3: AIA data using T_start and T_stop.

1. Reset the page.In the recordset box on the top of the page, type in :"aia.lev1[2011.01.01_01:30/5m][? WAVELNTH=171 ?]". Click Recount. You should get a Record count of 25.
2. Now click Method "url" and under Processing , click "hg_patch".
3. From the series drop down menu, pick aia.lev1
4. Neave the NOAA number blank and in T_START type in: 2011.01.01_01:30:00_TAI. In T_STOP:type in 2011.01.01_01:35:00_TAI.
5. In the Cadence put in 24s.Note that we are asking for 12 sec cadence data at 24s, so a multiple of 12.
6. Go with value For T_REF, you can put in the starting time, ie. 2011.01.01_01:30:00_TAI
7. Then enter e.g. 500 in both width and height of the box sizes.
8. put in a value for X and Y say, 1200 and 1500.(theses are CCD pixels )
9. In the protocol box check mpeg.
10. Again Ignore the colortable etc. They are not quite functional yet.
11. Enter your email address in the notify box and click submit.
12. After about 10-12 seconds, move down to the darker blue panel and click on submit status request. Its a good idea to wait as sometimes the requests havent gotten through and its messes up things.
13. Click submit again to determine the status of your request. Your images and movie should soon be ready. Click on the url that you are pointed to.

Good resource for Coordinate systems for solar image data by W. T. Thompson

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