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!!!Extracting HARP data from the JSOC

For information about HMI Active Region Patches (HARPs) and, in particular, the difference between HARPs, SHARPs and MHARPs please visit the [JSOC HARP page|http://jsoc.stanford.edu/HMI/HARPS.html]. Below I describe ways of accessing some useful information from the HARPs.

The following Open Access paper has more information about the HMI pipeline that generates the HARP data:
[Hoeksama et al. (2014, Solar Physics, 289, 3483)|https://ui.adsabs.harvard.edu/link_gateway/2014SoPh..289.3483H/doi:10.1007/s11207-014-0516-8]

!!Constructing a query with Lookdata

The first thing to note is that active regions are assigned a HARPNUM, but this is different from the NOAA active region number. The chances are you will know your active region's NOAA number, but not its HARPNUM.

To construct a query for the NOAA number, go to the [LookData page|http://jsoc.stanford.edu/ajax/lookdata.html] and enter, click on the 'RecordSet Select' tab, and type the following in the text box,

{{{
hmi.sharp_720s[][2011.02.13/1d][? NOAA_ARS ~ "11158" ?]
}}}

you should see that 120 entries are found. Since HARPs are derived from 720s cadence data, then this shows that all of the HARP data-sets for 13-Feb-2011 have been found.

!!Average active region properties

There are a number of parameters that are averaged or summed over the active region as a whole. It is then easy and quick to extract these for a time period (e.g., the passage of the AR across the disk). Each parameter is assigned a keyword, and you see the complete list by clicking on the 'Series Content' tab of the LookData page. Useful ones are:

USFLUX - total, unsigned magnetic flux in Maxwells.\\
MEANGAM - angle of the average magnetic field vector in degrees (90 corresponds to radial field).\\
AREA - area in micro solar hemispheres (mH). To convert to cm%%sup 2/%, multiply by 3.044 x 10%%sup 16/%.\\
T_OBS - time of observation.\\
HARPNUM - it's a good idea to print your region's HARP number.

Be careful with the following parameters:

MTOT - total line-of-sight magnetic flux density (G), but JSOC lists it as magnetic flux in Wb.\\
SIZE - projected area in mH/2 units, i.e., SIZE = 2 x AREA for region at disk center.

From the 'Series Content' page, you can de-select all keywords and then select just the ones you want. After doing this, go to the 'RecordSet Select' tab. In Box 4 you will see the keywords you selected. Select these with your mouse. In the bottom-left, click on 'Prepare keyword table in plain text format', and then click on the 'Fetch keyword values...' button. You'll then see an ASCII table containing your parameters as a function of time.


!!SHARP files

Once you know your HARP number (HARPNUM), then you can download the SHARP data from the JSOC. Go to the usual [ExportData page|http://jsoc.stanford.edu/ajax/exportdata.html] and type the following into the RecordSet box:

{{{
hmi.sharp_720s[7237][2018.02.11_07:00/3h]
}}}

which downloads three hours of data for AR 12699 (HARPNUM=7237) from 11-Feb-2018. For each time step you'll receive 31 FITS files. Each file contains a rectangular image containing the active region. Note that the pixel map that defines the active region area is stored in the 'bitmap' file. This image has 3 levels defining: the active region pixels for that particular image (highest value); the active region pixels for the complete evolution (middle value); and the pixels not part of the active region definition (lowest level).