期刊
ASTROPHYSICAL JOURNAL
卷 752, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/752/2/109
关键词
Sun: photosphere; sunspots; techniques: photometric
资金
- Spanish MICINN [AYA2011-29833-C06-04, PCI2006-A7-0624]
- Junta de Andalucia [P07-TEP-2687]
- European FEDER funds
- STFC [ST/H000429/1, PP/D002907/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H000429/1, PP/D002907/1] Funding Source: researchfish
- UK Space Agency [ST/J001732/1] Funding Source: researchfish
High-resolution blue continuum filtergrams from Hinode are employed to study the umbral fine structure of a regular unipolar sunspot. The removal of scattered light from the images increases the rms contrast by a factor of 1.45 on average. Improvement in image contrast renders identification of short filamentary structures resembling penumbrae that are well separated from the umbra-penumbra boundary and comprise bright filaments/grains flanking dark filaments. Such fine structures were recently detected from ground-based telescopes and have now been observed with Hinode. A multi-level tracking algorithm was used to identify umbral dots (UDs) in both the uncorrected and corrected images and to track them in time. The distribution of the values describing the photometric and geometric properties of UDs is more easily affected by the presence of stray light while it is less severe in the case of kinematic properties. Statistically, UDs exhibit a peak intensity, effective diameter, lifetime, horizontal speed, and a trajectory length of 0.29I(QS), 272 km, 8.4 minutes, 0.45 km s(-1), and 221 km, respectively. The 2 hr 20 minute time sequence depicts several locations where UDs tend to appear and disappear repeatedly with various time intervals. The correction for scattered light in the Hinode filtergrams facilitates photometry of umbral fine structure, which can be related to results obtained from larger telescopes and numerical simulations.
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