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Astron. Astrophys. 327, 795-799

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Estimation of the depths of initial anchoring and the rising-rates
of sunspot magnetic structures from rotation frequencies
of sunspot groups

J. Javaraiah and M.H. Gokhale

Indian Institute of Astrophysics, Bangalore - 560 034, India

Received 11 April 1997 / Accepted 1 July 1997


The mean variation of the `initial' rotation frequency of sunspot groups, with the life span of spot groups in the range 12 to 2 days, has its trend similar to the radial variation of plasma rotation frequency, FORMULA, across the convective envelope at 15o latitude as given by helioseismology.

The mean variation, with age, of the rotation frequency of sunspot groups which live for 10-12 days in latitudes 10o-20o also has its trend similar to FORMULA.

These results suggest: (i) In all latitudes, the magnetic structures (e.g, bunch of flux tubes) of spot groups which live for 2 days are initially anchored near the surface (radial distance FORMULA Mm), and those of spot groups which live successively longer are initially anchored in successively deeper layers, by FORMULA 21000 km per day, (ii) the structures which yield spot groups living 10-12 days are initially anchored near the base of the convective envelope.

For a spot group which lives 10-12 days in latitudes 10o-20o, the `anchoring layer' of its magnetic structure rises at a rate FORMULA km day-1, as the spot group ages.

Key words: Sun: sunspots - Sun: rotation

Send offprint requests to: J. Javaraiah

© European Southern Observatory (ESO) 1997

Online publication: October 14, 1997
Last change: April 6, 1998