EDP Sciences
Free access
Volume 437, Number 1, July I 2005
Page(s) 297 - 302
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20042495

A&A 437, 297-302 (2005)
DOI: 10.1051/0004-6361:20042495

Flares associated with abnormal rotation rates: Longitudinal minimum separation of leading and following sunspots

K. M. Hiremath1, G. S. Suryanarayana1 and M. R. Lovely1, 2

1  Indian Institute of Astrophysics, Bangalore-560034, India
    e-mail: hiremath@iiap.res.in
2  Sree Krishna College, Guruvayur, Kerala-680102, India

(Received 7 December 2004 / Accepted 1 February 2005 )

Using six years (1969-1974) of data of sunspot groups from the white light pictures of the Kodaikanal Observatory, we compute rotation rates of the leading and the following sunspots and the rate of change of longitudinal separation during their life times. We find that (i) the spots that are associated with abnormal rotation rates (i.e, rotation rates that are greater than 1$\sigma$ from the mean rotation) and that approach at a separation rate of $1{-}2\,$deg/day also experience minimum longitudinal separation (~ $6^{\circ}{-}10^{\circ}$) of their foot points during the course of their evolution; (ii) spots that have a minimum separation eventually trigger flares; and (iii) events with abnormal rotation rates and minimum approaching distances of the foot points occur on average during between $50{-}80\%$ of the life spans, indicating the annihilation of magnetic energy, probably below the surface. These results support the conventional physical scenario of magnetic reconnection that may be responsible for triggering flares.

Key words: sunspots -- Sun: flares

SIMBAD Objects in preparation

© ESO 2005