1 research outputs found
Photospheric Signatures of Granular-scale Flux Emergence and Cancellation at the Penumbral Boundary
We studied flux emergence events of sub-granular scale in a solar active
region. New Solar Telescope (NST) of Big Bear Solar Observatory made it
possible to clearly observe the photospheric signature of flux emergence with
very high spatial (0".11 at 7057{\AA}) and temporal (15 s) resolution. From TiO
observations with the pixel scale of 0".0375, we found several elongated
granule-like features (GLFs) stretching from the penumbral filaments of a
sunspot at a relatively high speed of over 4 km s-1. After a slender arched
darkening appeared at a tip of a penumbral filament, a bright point (BP)
developed and quickly moved away from the filament forming and stretching a
GLF. The size of a GLF was approximately 0.5" wide and 3" long. The moving BP
encountered nearby structures after several minutes of stretching, and a
well-defined elongated shape of a GLF faded away. Magnetograms from SDO/HMI and
NST/IRIM revealed that those GLFs are photospheric indicators of small-scale
flux emergence, and their disappearance is related to magnetic cancellation.
From two well-observed events, we describe detailed development of the
sub-structures of GLFs, and different cancellation processes that each of the
two GLFs underwent.Comment: Accepted for publication in The Astrophysical Journa