The Rotating Sunspot in AR 10930 |
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| Authors: | Soonyoung Min Jongchul Chae |
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| Institution: | (1) Department of Physics and Astronomy, Seoul National University, Seoul, 151-747, Korea |
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| Abstract: | We study the pattern and behavior of a rotating sunspot in Active Region 10930. The rotational angular speed has been extracted
from the apparent motions of the sunspot determined by applying a new optical technique – called non-linear affine velocity
estimator (NAVE) – to high-resolution G-band images taken by the Solar Optical Telescope (SOT) onboard the Hinode satellite. The structure and dynamics of coronal loops in this active region have been examined using the images obtained
by the X-Ray Telescope (XRT) and the spectral data taken by the Extreme-ultraviolet Imaging Spectrometer (EIS), both also onboard Hinode. Our results are summarized as follows: i) The small sunspot of positive polarity rotated counterclockwise about its center by 540° during the period of five days.
ii) Its angular velocity varied with the azimuth angle as well as the radial distance, being affected by the asymmetric shape
of the umbra. iii) The angular velocity increased up to 8° h−1 until 13 December as the sunspot grew, and then decreased rapidly down to 3° h−1 on the next day as the sunspot decayed. iv) The coronal loops that connected the two sunspots became sigmoidal in shape. v) The coronal emissions from the regions around the rotating sunspot were blueshifted, which may indicate the expansion of
the coronal loops. Our results suggest that the rotation of the sunspot may be closely related to the dynamic development
of emerging twisted magnetic fields. |
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| Keywords: | Sunspots magnetic fields Magnetic fields photosphere Magnetic fields corona |
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