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Role of Sunspot and Sunspot-Group Rotation in Driving Sigmoidal Active Region Eruptions
Solar Physics, 2006We study active region NOAA 9684 (N06L285) which produced an X1.0/3B flare on November 4, 2001 associated with a fast CME (1810 km s−1) and the largest proton event (31 700 pfu) in cycle 23. SOHO/MDI continuum image data show that a large leading sunspot rotated counter-clockwise around its umbral center for at least 4 days prior to the flare. Moreover,
Lirong Tian, David Alexander
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A Unique High-Latitude Sunspot Group
Publications of the Astronomical Society of the Pacific, 1957The present sunspot cycle, No. 19, has proved to be exceptional in several respects. One of these is in the number of highlatitude groups which have all or at least some members at or above ± 40° latitude and have lasted more than one day. Normally a few high-latitude groups appear during a cycle, mostly near sunspot minimum.
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Cycle latitude effects for sunspot groups
Solar Physics, 1991Digitized Mount Wilson sunspot data from 1917 to 1985 are analyzed to examine meridional motion and rotation properties as a function of latitude and distance (ξ) from the average latitude of activity (ξ0) in each hemisphere. Latitude dependence similar to previous results is found, but only for spot groups whose areas are decreasing from one day to ...
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Sunspot Groups as Tracers of Sub-Surface Processes
International Astronomical Union Colloquium, 2000AbstractData on sunspot groups have been quite useful for obtaining clues to several processes on global and local scales within the sun which lead to emergence of toroidal magnetic flux above the sun’s surface. I present here a report on such studies carried out at Indian Institute of Astrophysics during the last decade or so.
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Automated Detection of Sunspots and Sunspot Groups in Full-Disk Solar Images
2010In this paper, a new adopted unsupervised segmentation technique is presented. This technique extracts both sunspots and sunspot groups from the solar disk as whole group that eases the automated sunspot group classification. MacIntosh Classification is used as standard to determine which group belongs to which class.
Sarab F. Majed +2 more
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Large Sunspot Group of February 1935
Nature, 1935ALTHOUGH the sunspot group referred to in NATURE of February 16 (p. 260) was not specially large, it was of interest because of its very rapid growth. Spectro-heliograms in K2, 3, 2 light were secured through thin cloud at the Solar Physics Observatory, Cambridge, on February 5, 6 and 7.
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