Properties of Umbral Dots as Measured From the New Solar Telescope Data and MHD Simulations

Kılçık, Ali; Yurchyshyn, Vasyl; Rempel, Matthias; Abramenko, V. I.; Kitai, Reizaburo; Goode, Philip R.; Cao, Wenda; Watanabe, Hiroko

doi:10.1088/0004-637x/745/2/163

Cited by 24 publications

(36 citation statements)

References 34 publications

(59 reference statements)

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“…The scatter plot derived from PLGs shows a distribution similar to that found by Berrilli et al (2002) and Yu et al (2011) in their studies on quiet-Sun granulation. Indeed, the UDs distribution revealed from our study is not in agreement with the results found by Kilcik et al (2012) and Ji et al (2016). The LBGs distribution is similar to the UDs distribution, although for LBGs the range of intensity values is shifted into higher intensities.…”

Section: Resultscontrasting

confidence: 95%

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Comparison of different populations of granular features in the solar photosphere

Falco

Puglisi

Guglielmino³

et al. 2017

A&A

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Context. The granulation is the most visible manifestation of convective motions occurring in the uppermost layers of the solar convection zone. Strong magnetic fields hinder these motions, but the appearance of bright structures such as umbral dots (UDs) and light bridges (LBs) in sunspots also shows that in strong magnetic field regions, the convection is not completely suppressed. Aims. We aim to investigate the properties of the granules identified by a new segmentation algorithm in regions characterized by different magnetic field strength, in order to improve the current knowledge of the mechanism behind the appearance of the different bright structures in sunspots. Methods. We analyzed data acquired by the CRisp Imaging SpectroPolarimeter at the Swedish Solar Telescope on 6 August 2011 relevant to a large sunspot with a LB observed in NOAA AR 11263. We applied a new segmentation algorithm to the data acquired along the Fe I 630.15 nm line. Results. We found that the granules in the LB have a diameter between 0. 22 and 0. 99, that is, smaller than the granules in a nearby plage region (PL) and similar to those of the UDs. We observed values of the mean continuum intensity between 0.42 I c and 0.98 I c for the LB granules, which are similar to those of the UDs. PL granules have higher values, probably reflecting different conditions of the plasma convection. Mean Doppler velocity and mean magnetic field strength have been studied and even for these physical parameters we found similar values between LB granules and UDs. Conclusions. Different values for the physical properties analyzed have been found between the granules of the PL and LB granules of the three analyzed solar regions. In particular, we show that the granules in PL and sunspot regions have different physical properties. This clearly depends on the different physical conditions of the regions where these two kind of granular structures are embedded. We also confirm the recent findings on the similarity between granules in PL and quiet Sun regions. We show values of the various physical quantities analyzed in PL granules in agreement with those reported in the literature for quiet Sun granules. Finally, a noteworthy result is that the granules observed in the faint LB have physical properties similar to those found for UDs.

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Section: Resultscontrasting

confidence: 95%

“…The results of the UDs physical properties obtained in the last decade are summarized in Table 2. Taking into account the most recent results, the UDs diameters observed by Kilcik et al (2012) cover the range between 0 . 23 and 0 .…”

Section: Individual Featuresmentioning

confidence: 86%

Comparison of different populations of granular features in the solar photosphere

Falco

Puglisi

Guglielmino³

et al. 2017

A&A

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“…The velocity range of CUDs is between 0.19 and 0.38 km s −1 and that of PUDs between 0.45 and 0.51 km s −1 (see Table 3); the horizontal velocity of CUDs is slower than that of PUDs. Watanabe, Kitai, and Ichimoto (2009) and Kilcik et al (2012) concluded that PUDs have a relatively fast horizontal velocity because they are located in regions with a strong horizontal component of the magnetic field and/or a strongly inclined field. Our findings confirm their conclusions.…”

Section: Ud Propertiesmentioning

confidence: 99%

Investigation of Umbral Dots with the New Vacuum Solar Telescope

Jiang

Feng

et al. 2015

Sol Phys

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Umbral dots (UDs) are small isolated brightenings observed in sunspot umbrae. They are convective phenomena existing inside umbrae. UDs are usually divided into central UDs (CUDs) and peripheral UDs (PUDs) according to their positions inside an umbra. Our purpose is to investigate UD properties and analyze their relationships, and further to find whether or not the properties depend on umbral magnetic field strengths. Thus, we selected high-resolution TiO images of four active regions (ARs) taken under the best seeing conditions with the \textit{New Vacuum Solar Telescope} in the Fuxian Solar Observatory of the Yunnan Astronomical Observatory, China. The four ARs (NOAA 11598, 11801, 12158, and 12178) include six sunspots. A total of 1220 CUDs and 603 PUDs were identified. Meanwhile, the radial component of the vector magnetic field of the sunspots taken with the \textit{Helioseismic and Magnetic Imager} on-board the \textit{Solar Dynamics Observatory} was used to analyze relationships between UD properties and umbral magnetic field strengths. We find that diameters and lifetimes of UDs exhibit an increasing trend with the brightness, but velocities do not. Moreover, diameters, intensities, lifetimes and velocities depend on the surrounding magnetic field. A CUD diameter was found larger, the CUD brighter, its lifetime longer, and its motion slower in a weak umbral magnetic field environment than in a strong one.Comment: 16 Pages, 7 Figures, and 5 Tables, accepted for publication in Solar Physic

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“…A UD is a unique cosmic phenomenon for understanding magnetoconvection with both spatially and temporarily resolved observations. Such studies that compare with the numerical simulation and the observed properties is possible owing to this rich data set (Bharti et al 2010;Kilcik et al 2012). There are other magnetoconvection manifestation in the universe, such as the accretion disk and the low temperature stars, although those are very far and so tracking the temporal evolution of their magnetoconvective cells is almost impossible.…”

Section: Resultsmentioning

confidence: 99%

Observations of umbral dots and their physical models

Watanabe

2014

Publications of the Astronomical Society of Japan

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The Hinode satellite opens a new era to the sunspots research, because of its high spatial resolution and temporal stability. Fine scale structures in sunspots, called umbral dots (UDs), have become one of the hottest topics in terms of the close observation of the magnetoconvection.In this paper, a brief review of observed properties of UDs is given based on the recent literature. UDs born in the periphery of the umbra exhibit inward migration, and their speeds are positively correlated with the magnetic field inclination. Longerlasting UDs are tend to be larger and brighter, while lifetimes of UDs show no relation with their background magnetic field strength. UDs tend to disappear or stop its proper motion by colliding with the locally strong field region. The spatial distribution of UD is not uniform over an umbra but is preferably located at boundaries of cellular patterns. From our 2-dimensional correlation analysis, we measured the characteristic width of the cell boundaries (≈0.5 ′′ ) and the size of the cells (≈6 ′′ ).Then we performed a simplified analysis to get statistics how the UD distribution is random or clustered using the Hinode blue continuum images. We find a hint that the UDs become less dense and more clustered for later phase sunspots. These results may be related to the evolutional change of the subsurface structure of a sunspot.Based on these observational results, we will discuss their physical models by means of numerical simulations of magnetoconvection.

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Properties of Umbral Dots as Measured From the New Solar Telescope Data and MHD Simulations

Cited by 24 publications

References 34 publications

Comparison of different populations of granular features in the solar photosphere

Comparison of different populations of granular features in the solar photosphere

Investigation of Umbral Dots with the New Vacuum Solar Telescope

Observations of umbral dots and their physical models

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