Estimation of the depths of initial anchoring and the rising-rates of sunspot magnetic structures from rotation frequencies of sunspot groups
J. Javaraiah and
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, , across the convective envelope at 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 also has its trend similar to .
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 Mm), and those of spot groups which live successively longer are initially anchored in successively deeper layers, by 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 , the 'anchoring layer' of its magnetic structure rises at a rate km day-1, as the spot group ages.
Key words: Sun: sunspots Sun: rotation
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© European Southern Observatory (ESO) 1997
Online publication: April 6, 1998