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Science 7 December 2007:
Vol. 318. no. 5856, pp. 1597 - 1599
DOI: 10.1126/science.1146337
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Reports

Twisting Motions of Sunspot Penumbral Filaments

K. Ichimoto,1* Y. Suematsu,1 S. Tsuneta,1 Y. Katsukawa,1 T. Shimizu,2 R. A. Shine,3 T. D. Tarbell,3 A. M. Title,3 B. W. Lites,4 M. Kubo,4 S. Nagata5

The penumbra of a sunspot is composed of numerous thin, radially extended, bright and dark filaments carrying outward gas flows (the Evershed flow). Using high-resolution images obtained by the Solar Optical Telescope aboard the solar physics satellite Hinode, we discovered a number of penumbral bright filaments revealing twisting motions about their axes. These twisting motions are observed only in penumbrae located in the direction perpendicular to the symmetry line connecting the sunspot center and the solar disk center, and the direction of the twist (that is, lateral motions of intensity fluctuation across filaments) is always from limb side to disk-center side. Thus, the twisting feature is not an actual twist or turn of filaments but a manifestation of dynamics of penumbral filaments with three-dimensional radiative transfer effects.

1 National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Toyko 181-8588, Japan.
2 Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan.
3 Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, CA 94304, USA.
4 High Altitude Observatory, National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307-3000, USA.
5 Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan.

* To whom correspondence should be addressed. E-mail: ichimoto{at}solar.mtk.nao.ac.jp

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Sunspot Flows and Filaments.
G. Scharmer (2009)
Science 325, 155-156
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Penumbral Structure and Outflows in Simulated Sunspots.
M. Rempel, M. Schussler, R. H. Cameron, and M. Knolker (2009)
Science 325, 171-174
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