EDP Sciences
Free access
Volume 371, Number 2, May IV 2001
Page(s) 731 - 737
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20010429

A&A 371, 731-737 (2001)
DOI: 10.1051/0004-6361:20010429

Submergence of magnetic flux in interaction of sunspot groups

B. Kálmán

Heliophysical Observatory of the Hungarian Academy of Sciences, PO Box 30, Debrecen, Hungary

(Received 13 December 2000 / Accepted 2 March 2001 )

Submergence of magnetic flux is demonstrated in the process of evolution of sunspot groups NOAA 6850 (26 Sep.-07 Oct. 1991) and 7220/22 (06-17 July 1992). In both cases new magnetic flux emerges immediately behind an existing spotgroup. The new flux does not interact with the old one, as can be seen in YOHKOH X-ray images, so no significant flare activity occurs, although umbrae of different magnetic polarity collide. In both cases the quickly forward moving p-spots of the new flux force the submergence of the f-spots of the older region, these being squeezed from two sides between the old and new p-spots. This leads to the disappearance of about 16 1021 Mx of f-polarity in AR 6850. In the case of this region the submerged flux interacts with newly emerging magnetic fields and in the next rotation continues its life as the complex and eruptive AR 6891. In AR 7220/22, spots of both polarities submerge in the intermediate part of the complex between the old leader of AR 7220 and the quickly growing AR 7222, leaving in the next rotation a bipolar-looking group (AR 7248), consisting of two p-polarity spots. So, submergence of magnetic flux due to interaction of old and new activity may play an important role in the decay of sunspot groups.

Key words: Sun: activity -- Sun: magnetic fields -- sunspots

Offprint request: B. Kálmán, kalman@tigris.klte.hu

© ESO 2001