Solar Magnetic Tracking. III. Apparent Unipolar Flux Emergence in High-resolution Observations

Derek Lamb, Craig DeForest, Hermance Hagenaar, Clare Elizabeth Parnell, Brian Welsch

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


Understanding the behavior of weak magnetic fields near the detection limit of current instrumentation is important for determining the flux budget of the solar photosphere at small spatial scales. Using 0farcs3-resolution magnetograms from the Solar Optical Telescope's Narrowband Filter Imager (NFI) on the Hinode spacecraft, we confirm that the previously reported apparent unipolar magnetic flux emergence seen in intermediate-resolution magnetograms is indeed the coalescence of previously existing flux. We demonstrate that similar but smaller events seen in NFI magnetograms are also likely to correspond to the coalescence of previously existing weak fields. The uncoalesced flux, detectable only in the ensemble average of hundreds of these events, accounts for 50% of the total flux within 3 Mm of the detected features. The spatial scale at which apparent unipolar emergence can be directly observed as coalescence remains unknown. The polarity of the coalescing flux is more balanced than would be expected given the imbalance of the data set, however without further study we cannot speculate whether this implies that the flux in the apparent unipolar emergence events is produced by a granulation-scale dynamo or is recycled from existing field.
Original languageEnglish
Pages (from-to)1405-1416
Number of pages12
JournalAstrophysical Journal
Issue number2
Publication statusPublished - Sept 2010


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