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HMI Active Region Patches

HMI Active Region Patches. Michael Turmon JPL/Caltech. Mask and Patch Data Products. Mask: 2011/02/14 12:00. Magnetograms (M_720s) + intensitygrams (Ic_720s) yield activity masks (Marmask_720s). Active clumps in Marmask_720s are grouped into “instantaneous patches” (Mpatch_720s)

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HMI Active Region Patches

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  1. HMI Active Region Patches Michael TurmonJPL/Caltech

  2. Mask and Patch Data Products Mask: 2011/02/14 12:00 • Magnetograms (M_720s) + intensitygrams (Ic_720s) yield activity masks (Marmask_720s). • Active clumps in Marmask_720s are grouped into “instantaneous patches” (Mpatch_720s) • The instantaneous patches are linked temporally using an overlap metric to produce HARPs (HMI ARPatch) • A HARP is about the scale of a NOAA active region. • We have its entire history. zoom HARP (text overlayin this imageis flipped)

  3. HARP Geometry • HARPs are a simple concept, but their geometry can be complex. • They are often not “simply connected” • I.e., a single HARP can consist of multiple compact blobs • Their configuration is unknown until final demise • HARPs are retrospectively pasted together (“merged”) as future growth is observed One Day Earlier HARPs: 2011/02/14 12:00 One Day Later

  4. Delivering the HARPs as a Data Product • HARPs are a sequence of cut-outs from the original image set. • To use, you shift the cut-out to the correct place in M_720s, etc. • There is no complex transformation. Just a shift in pixel coordinates. • In JSOC, the HARP data series is indexed by HARP number, analogous to NOAA AR number, and time. • Encoding: on-HARP (orange patch) is ≥ 64; active area within HARP is 66; inactive within HARP is 65. (Using symbolic KWs) Mag: 2011/02/14 12:00 Instantaneous bounding box HARP bounding box (bigger) HARP origin

  5. What the HARP is aimed at • Why is the HARP bounding box larger than the instantaneous bounding box? How is that size determined? • Note: You do need not to know or remember these details. • We want the HARP to be in image coordinates for ease-of-use, but we also want the HARP to be a consistent size for AR studies • Key: The HARP cutout is made as if seen by observer hovering above the AR, moving at a constant angular rate (deg. lon/day). • Per-HARP angular rate determined from differential rotation formula in powers of sin2(lat) evaluated at HARP centroid in latitude, and encoded in HARP KWs. • The dimensions (degrees lon X degrees lat) of the HARP is given by the smallest lat-lon bounding box that encompasses all presentations of the HARP from birth to death. • HARPs have equal extent in longitude => they are “tall” at the limb.

  6. Graphical Overview of HARP Sizing • Orange pixels are on-HARP; black pixels are active. The white line marks the instantaneous bounding box (in image-pixel coordinates). • The blue dots mark the lat-lon center of the HARP. The center has a constant latitude and advances in longitude with constant rate. • The red boxes show a fixed-size lat-lon bounding box, centered on the blue dots, which encompasses all HARP pixels at all times. • The HARP is the smallest image-domain box containing the red boxes. Time   Same lat/lon 

  7. Acknowledgement The research described in this paper was carried out in part by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

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