Extracting HARP data from the JSOC#

This page only contains basic information about using this service, and it is work in progress. Please refer to the JSOC page directly for full details.

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 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.

Total magnetic flux#

One useful quantity to extract from the HARPs is the total magnetic flux: either positive (MPOS_TOT), negative (MNEG_TOT) or absolute (MTOT). To get these, go to Box 4 on the LookData page and find the keywords in the list. Select them, and then look in the bottom-left of the LookData page and click on the 'Prepare keyword table in plain text format', and then click the 'Fetch keyword values for RecordSet' button. You will then a see a plain ascii file containing the values.

Note that the flux is given in units of Webers, and also note that is for the whole HARP area. To get the area, you will also need to get the keyword SIZE for the projected area of the region. Dividing by SIZE gives the magnetic flux density (measured in Tesla or Gauss). Note that the unit of SIZE is micro-hemispheres (mH), which I guess is 2*pi*R_sun^2*10^-6.