Computer Science
Scientific paper
Feb 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003esasp.517..291h&link_type=abstract
In: Proceedings of SOHO 12 / GONG+ 2002. Local and global helioseismology: the present and future, 27 October - 1 November 2002,
Computer Science
Sunspots, Torsional Oscillations
Scientific paper
High-resolution (0.6 arc sec/pixel) MDI data maps with two single sunspots seen in brightness, line-of-sight velocity and magnetic field are analyzed. Using the assumption of the cylindrical symmetry, the radial, tangential and vertical components of the velocities are calculated for a number of distances from the center of the sunspot to its penumbral outer limit. Time variations of these components show significant power in a period range near 2-5 days and in the well-known 5-min band. The power in the 5-min region would be associated with interaction between acoustic oscillations and the sunspot structure. Analysis of the velocity components vs. distance from the center of spot shows no substantial temporal variations for both radial and vertical ones. Nevertheless, the tangential velocity component is changed significantly and reverses its sign to the opposite one. The most important velocity changes are located near the outer limit of the spot's umbra. This phenomenon can be interpreted as a torsional oscillation of the sunspot. An explanation of this oscillation feature is presented and discussed.
Didkovsky Leonid V.
Haneychuk V. I.
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