Tilt and α _best of major flare-producing active regions
Yang Liu Submitted: 2003-07-18 10:16
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 α
m best 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
m best, and the tilt and the α
m best of all
86 regions are positively correlated. (4) 33 (60%) of the 55
active regions which have an etagammadelta magnetic configuration
show the same sign for the tilt and α
It is commonly believed that the sign of the tilt and α
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. 1999).
Authors: Lirong Tian, Y. Liu
Publication Status: A&Ap. Lett. (accepted)
Last Modified: 2003-07-18 10:16