Variations of the 3‐D coronal magnetic field associated with the X3.4‐class solar flare event of AR 10930

Abstract

The variations of the 3-D coronal magnetic fields associated with the X3.4-class flare of active region 10930 are studied in this paper. The coronal magnetic field data are reconstructed from the photospheric vector magnetograms obtained by the Hinode satellite and using the nonlinear force-free field extrapolation method developed in our previous work (He et al., 2011). The 3-D force-free factor , 3-D current density, and 3-D magnetic energy density are employed to analyze the coronal data. The distributions of and current density reveal a prominent magnetic connectivity with strong negative values and strong current density before the flare. This magnetic connectivity extends along the main polarity inversion line and is found to be totally broken after the flare. The distribution variation of magnetic energy density reveals the redistribution of magnetic energy before and after the flare. In the lower space of the modeling volume the increase of magnetic energy dominates, and in the higher space the decrease of energy dominates. The comparison with the flare onset imaging observation exhibits that the breaking site of the magnetic connectivity and site with the highest values of energy density increase coincide with the location of flare initial eruption. We conclude that a cramped positive region appearing in the photosphere causes the breaking of the magnetic connectivity. A scenario for flare initial eruption is proposed in which the Lorentz force acting on the isolated electric current at the magnetic connectivity breaking site lifts the associated plasmas and causes the initial ejection.

The magnetic field in the solar atmosphere

“…Force-free modeling suggests energy storage rates of a few 10 23 J h −1 to a few 10 25 J h −1 Sun et al 2012b;Malanushenko et al 2014;He et al 2014, and see also Fig. 15a).…”

“…However, there have been doubts about the reliability of the latter owing to very uncertain estimates. Often also a decrease of the free energy occurs already before the time of the peak SXR flux of a flare, and in other cases this has been seen even before the flare onset (Jing et al 2009;He et al 2014).…”

Chirality and magnetic configuration associated with two-ribbon solar flares: AR 10930 versus AR 11158

“…In our scenario (see Figure 6 and He et al 2014), the breaking of magnetic connectivity causes ejection of some electric current (at the magnetic connectivity breaking site) in the core area (see Figure 4) Figure 5. The bars in the preflare α diagrams (golden color) represent the prominent magnetic connectivity as well as the associated strong electric current (see core area in Figure 4) formed before the flare; and the bars in the postflare α diagrams (light-blue color) indicate the two branches of the broken magnetic connectivity.…”

“…(Note that DBIE is an advancement of the original BIE method proposed by , see also Wang et al 2000Wang et al , 2001He & Wang 2006;He et al 2011. ) This method has been utilized to analyze the coronal magnetic structures for a variety of solar ARs (He & Wang 2008;He et al 2011He et al , 2012He et al , 2014Liu et al 2013;Wang et al 2013;Yang et al 2014;Wang et al 2015). Figure 2 displays the employed photospheric vector magnetograms before and after the two flare events.…”

“…Note that in the force-free magnetic field, α is a constant along each field line (see the description in Section 1). He et al (2014) studied the variations of α and current density distributions in AR 10930 (left columns of Figures 4 and 5) before and after the X3.4 flare eruption. Direction of Bt in Figure 2 a rightward (→) leftward (←) Sign of force-free factor α (see Figure 5) b negative (α < 0) positive (α > 0) Twist orientation of coronal magnetic field lines in Figure 3 c inverse S-shaped S-shaped Orientation of flare-ribbon distribution in Figure 1 d right-leaning ( ) left-leaning ( ) a The left-handed or right-handed chirality is defined by the morphological relation between the direction of Bt (the thumb pointing in) and the polarity orientation of Bz (pointing from the positive polarity to the negative polarity by the other four fingers with the palm facing the PIL) in photospheric vector magnetograms.…”