The change of magnetic inclination angles associated with the X3.4 flare on December 13, 2006

Abstract

Recent studies showed a consistent pattern of changes in the sunspot structure associated with major flares: part of the peripheral penumbral regions vanishes during flares, and meanwhile, the umbral cores and/or inner penumbral regions are darkened. To understand the underlying physics of these observations, we compare the magnetic inclination angle in the decayed peripheral and the enhanced inner penumbral regions before and after the 4B/X3.4 flare of 2006 December 13 by using the high-resolution vector magnetograms from Hinode. We find that the mean inclination angle in the decayed penumbra increases after the flare while that in the enhanced penumbra near flaring neutral line decreases. The result confirms the previous idea that two components of a δ sunspot become connected after flares. As a result of new connection, peripheral penumbral fields change from a more inclined to a more vertical configuration and transverse fields in umbral core and inner penumbral regions increase substantially (Liu et al. 2005). The flare-associated changes of Doppler width as well as other parameters (the transverse field strength, continuum intensity and filling factor) are also presented.