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 highresolution 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.Sun: magnetic fields, Sun: photosphere, Sun: flares As shown by magnetogram data from both groundbased and space-borne instruments, photospheric magnetic fields can experience some rapid, significant and permanent changes during X-and M-class solar flares. For instance, Wang et al. [1] detected a permanent increase in the magnetic flux of the leading polarity of active regions and a decrease in the following polarity based on a sample of six Xclass flares. Sudol and Harvey [2] conducted a survey of 15 X-class flares and found that abrupt and persistent changes in the photospheric magnetic flux are common features associated with X-class flares. At least two-third of the field changes occurred in the penumbral regions of sunspots. With the advanced non-linear force-free field modelling techniques [3] , Jing et al. [4] investigated the altitude variation of magnetic shear associated with the X3.4 flare of 2006 December 13. They found that magnetic shear increased after the flare around the flaring magnetic neutral line (NL) below a height of ∼8 Mm and decreased from that height to ∼70 Mm. Citation: Li Y X, Jing J, Tan C Y, et al. The change of magnetic inclination angles associated with the X3.4 flare on

Rapid Changes of Photospheric Magnetic Field After Tether-Cutting Reconnection and Magnetic Implosion

“…Namely, the transverse field near the magnetic polarity inversion line (PIL) at the core flaring region is enhanced rapidly and irreversibly, which is often accompanied by an increase of magnetic shear. Such a rapid change of vector PMFs closely associated with flares/CMEs has been consistently found later on using ground-based (Schmieder et al 1994;Wang et al 2002Wang et al , 2004bWang et al , 2005Wang et al , 2007Liu et al 2005;Su et al 2011) and Hinode observations (Jing et al 2008;Li et al 2009). Indirect evidence includes the unbalanced flux evolution of the line-of-sight magnetic field , the variation of the sunspot white-light structure in flaring regions (Wang et al 2004a;Deng et al 2005;Liu et al 2005;Chen et al 2007), and the change in the pattern of the penumbral Evershed flow (Deng et al 2011).…”

The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare

“…For example, a large increase in inclination angle for ROI 1 (Figure 3(d)) between the second and third scans is accompanied by a slight increase in field strength (Figure 3(a)), giving approximately no change in the horizontal field (Figure 3(b)). The Li et al (2009) result supports the reconnection picture of Liu et al (2005), whereby newly connected fields near the magnetic neutral line contributed to field inclination becoming more horizontal. This picture suggests that the field lines after the flare in our study become newly reconnected, low-lying, more horizontal field lines near the flaring neutral line.…”

“…Li et al (2009) also found a transverse-field increase of 20% after an X3.4 flare. We found no significant changes in transverse-field strength either immediately before or after the flare.…”

“…Previous studies have also reported changes in field orientation after a flare. Li et al (2009) found an inclination angle change of ≈ 5 • toward the horizontal in a region of enhanced Gband intensity after an X-class flare, and the inclination becoming more vertical by ≈ 3 • in a region of diminished G-band intensity. Although their study focuses on penumbral regions, the region becoming more horizontal after the flare is located close to the flaring neutral line, similar to our findings.…”

What determines the penumbral size and Evershed flow speed?

“…The authors interpret the sudden change of penumbral white light structure to be a result of the change of overall magnetic field inclination down to the photosphere due to magnetic reconnection in the flare, which was then confirmed by other authors (Sudol & Harvey 2005;Li et al 2009). …”