EDP Sciences
Free access
Issue
A&A
Volume 411, Number 3, December I 2003
Page(s) L497 - L500
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20031618


A&A 411, L497-L500 (2003)
DOI: 10.1051/0004-6361:20031618

Letter

The flares associated with the abnormal rotation rates of the bipolar sunspots: Reconnection probably below the surface

K. M. Hiremath1 and G. S. Suryanarayana2

1  Indian Institute of Astrophysics, Bangalore-560034, India
2  Indian Institute of Astrophysics, Kodaikanal-624103, India

(Received 26 September 2003 / Accepted 14 October 2003 )

Abstract
We use the observations of Kodaikanal observatory white light pictures to study the association between the rotation rates of the bipolar sunspots and triggering of the flares. For the years 1969-1974, we compute daily rotation rates of the leading and the following spots of the bipolar sunspot groups during their life span. We find that either leading or following or both of the bipolar spot groups which have abnormal rotation rates during the course of their evolution are strongly associated with the occurrence of flares in the later stage of their life span. Other important findings are: (i) the abnormal rotation rates and the flares occur during the $50{-}80\%$ of their life span of the spot group and, (ii) abnormal rotation rate of about $2^{\circ}$/day is required for triggering the flares. The strong relation between the occurrence of abnormal rotation rates of the sunspot groups and the occurrence of the flares enabled us to estimate the probable region of depth of reconnection below the solar surface.


Key words: bipolar sunspots -- abnormal rotation rates -- flares -- flux tubes

Offprint request: K. M. Hiremath, hiremath@iiap.ernet.in




© ESO 2003

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