The crossover effect in sunspots and the fine structure of penumbra

Golovko, A. A.

doi:10.1007/bf00157848

Cited by 20 publications

(9 citation statements)

References 7 publications

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“…First, one can assume the existence of unresolved structure when analyzing the data, in particular when interpreting spectral line asymmetries (e.g., Bumba 1960;Grigorjev & Katz 1972;Golovko 1974;Sánchez Almeida & Lites 1992;Wiehr 1995;Solanki & Montavon 1993;Bellot Rubio 2004;Sánchez Almeida 2005). Via line fitting and with proper modeling, this indirect technique allows us to infer the physical properties of unresolved structures.…”

Section: Introductionmentioning

confidence: 99%

High‐Resolution Proper Motions in a Sunspot Penumbra

Márquez

Alméida

Bonet

2006

ApJ

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Local correlation tracking techniques are used to measure proper motions in a series of high angular resolution ($0B1) penumbra images. If these motions trace true plasma motions, then we have detected converging flows that arrange the plasma in long narrow filaments cospatial with dark penumbral filaments. Assuming that these flows are stationary, the vertical stratification of the atmosphere and the conservation of mass suggest downflows in the filaments on the order of 200 m s À1 . The association between downflows and dark features may be a sign of convection, as it happens with the nonmagnetic granulation. Insufficient spatial resolution may explain why the estimated vertical velocities are not fast enough to supply the radiative losses of penumbrae.

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Section: Introductionmentioning

confidence: 99%

High‐Resolution Proper Motions in a Sunspot Penumbra

Márquez

Alméida

Bonet

2006

ApJ

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“…Unscrambling the averages to retrieve properties of the unresolved structure is both difficult and prone to misinterpretation. Researchers have approached the problem by analyzing the data assuming the existence of unresolved structures (e.g., Bumba 1960;Grigorjev & Katz 1972;Golovko 1974;Sánchez Almeida & Lites 1992;Solanki & Montavon 1993;Wiehr 1995;Sánchez Almeida et al 1996;Westendorp Plaza et al 2001;Bellot Rubio 2004;Sánchez Almeida 2005). Then the outcome of the analysis depends on the specific assumptions, a difficulty that increases as the resolution worsens and the observational average becomes coarser.…”

Section: Introductionmentioning

confidence: 99%

The Evershed Effect Observed with 0.2″ Angular Resolution

Alméida

Márquez

Bonet

et al. 2007

ApJ

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We present an analysis of the Evershed effect observed with a resolution of 0.2 00 . Using the new Swedish 1 m Solar Telescope and its Littrow spectrograph, we scan a significant part of a sunspot penumbra. Spectra of the nonmagnetic line Fe i k7090.4 allows us to measure Doppler shifts without magnetic contamination. The observed line profiles are asymmetric. The Doppler shift depends on the part of the line used for measuring, indicating that the velocity structure of penumbrae remains unresolved, even with our angular resolution. The observed line profiles are properly reproduced if two components with velocities between zero and several km s À1 coexist in the resolution elements. Using Doppler shifts at fixed line depths, we find a local correlation between upflows and bright structures and between downflows and dark structures. This association is not specific to the outer penumbra, but it also occurs in the inner penumbra. The existence of such a correlation was originally reported in 1969 by Beckers and Schröter, and it is suggestive of energy transport by convection in penumbrae.

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“…Â íè aeíåé îá ëàñ òè ïî ðû Ð1 òàê aeå íà áëþ äà ëèñü àíî ìàëü íûå V-ïðîôè ëè ôî òîñ ôåð íûõ ëè íèé. Î íà áëþ äå íè ÿõ àíî ìàëü íûõ V-ïðî ôè ëåé ôî òîñ ôåð íûõ ëè íèé â ïî ëó òå íè ïÿ òåí è îêî ëî ïîð ñî îá ùà åò ñÿ, íà ïðèìåð, â ðà áî òàõ [9,10,12,[34][35][36]40]. Â áîëü øè íñòâå ðà áîò îíè îá ú ÿñíÿ þò ñÿ íà ëè ÷è åì ïðî òè âî ïî ëîae íûõ ïî ëÿð íîñ òåé.…”

Section: îáñóAeäåíèåunclassified

“…Îíè ñî ñòî ÿò èç òðåõ-÷å òû ðåõ äî ëåé. Â ðà áî òàõ [12,13] òà êîå ÿâ ëå íèå íà çû âà åò ñÿ êðîñ ñî âåð-ýô ôåê òîì. Âïåð âûå ýòîò ýô ôåêò îá íà ðó aeåí â ñî ëíå÷ íûõ ïÿò íàõ â ðà áî òå [17].…”

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