Letter to the Editor

Tilt and of major flare-producing active regions

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
² W.W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA

Corresponding author: L. R. Tian, tlr@ns.bao.ac.cn

Received: 21 March 2003
Accepted: 25 June 2003

Abstract

We surveyed 86 active regions in the years from 1996 to 2002 in the 23rd solar cycle that produced more than three major flares. We studied the systematic tilt angle with respect to the solar equator and the force-free parameter  of the magnetic field of the active regions, and we obtained the following results. (1) Only 46 (54%) of the active regions follow Joy's law. (2) 43 (50%) active regions obey the hemispheric helicity rule. (3) 56 (65%) have the same sign for the tilt and the , and the tilt and the  of all 86 regions are positively correlated. (4) 33 (60%) of the 55 active regions which have an  magnetic configuration show the same sign for the tilt and . 
It is commonly believed that the sign of the tilt and  obtained in the photosphere can describe the sign of the twist and writhe of the flux tube rising from the convection zone. Therefore, the results above appear to support the kink hypothesis for active regions that the sign of the twist and writhe should be the same where a kink instability has developed (Linton et al. [CITE]).