Photospheric signatures of granular-scale flux emergence and cancellation at the penumbral boundary

Document Type

Article

Publication Date

10-20-2011

Abstract

We studied flux emergence events of sub-granular scale in a solar active region. The New Solar Telescope (NST) of the Big Bear Solar Observatory made it possible to clearly observe the photospheric signature of flux emergence with very high spatial (011 at 7057) and temporal (15 s) resolution. From TiO observations with the pixel scale of 00375, we found several elongated granule-like features (GLFs) stretching from the penumbral filaments of a sunspot at a relatively high speed of over 4kms-1. After a slender arched darkening appeared at the 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 05 wide and 3″ long. The moving BP encountered nearby structures after several minutes of stretching, and the well-defined elongated shape of the GLF faded away. Magnetograms from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and NST/InfraRed Imaging Magnetograph 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. © 2011. The American Astronomical Society. All rights reserved.

Identifier

80053994989 (Scopus)

Publication Title

Astrophysical Journal

External Full Text Location

https://doi.org/10.1088/0004-637X/740/2/82

e-ISSN

15384357

ISSN

0004637X

Issue

2

Volume

740

Grant

0745744

Fund Ref

National Science Foundation

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