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GONG Magnetogram Data Products

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Sky-coordinate images• Single-site or merged?

– Single-site requires users to select.– Merge has lower noise, may require site-

specific correction to reduce jumps as stations change.

• At what cadence? – 1 min – highest cadence, most noise.– 3 min or 5 min – compromises.– 10 min – lowest cadence, least noise,

rotational smearing starts to be a concern.• Rotational smearing correction? How?

– Rotation crosses 1 pixel at disk center in about 15 min.

– Remap and average in heliographic coordinates, transform back to sky.

• What temporal filter/averaging algorithm?– Simple box car.– Hathaway filter (Gaussian).– Will need to specify width in any case.

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Remapped images

• Same questions as for sky images:– Single-site/merged– Cadence– Rotational smearing easy

to deal with– Temporal filter

• What spatial resolution for remapped images?– Currently 0.2°

• What projection for remapped images?– Currently longitude - sine

latitude

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Synoptic Maps• Single-site or merged? • At what cadence

– Trade-off between effort and science: What’s rapid enough for space weather?

– 1, 2, 4, 8 hours?• How to interact with SOLIS

cadence?– Identical times for

comparison?– Different times to fill in

temporal gaps ?• How to treat poles,

projection of LOS, missing data?