HMI Active Region Patches

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HMI Active Region Patches

• Michael TurmonJPL/Caltech

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Mask and Patch Data Products

• 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 AR
  Patch)
• A HARP is about the scale of a NOAA active
  region.
• We have its entire history.

Mask 2011/02/14 1200
zoom
HARP
(text overlayin this imageis flipped)
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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

HARPs 2011/02/14 1200
One Day Earlier
One Day Later
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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 1200
Instantaneous bounding box
HARP bounding box (bigger)
HARP origin
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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 gt they are
  tall at the limb.

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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 ?
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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.