1. Survey of Magnetic Field Parameters Associated With Large Solar Flares
- Author
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Li, Ting, Zheng, Yanfang, Li, Xuefeng, Hou, Yijun, Li, Xuebao, Zhang, Yining, and Chen, Anqin
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Until now, how the magnetic fields in M/X-class flaring active regions (ARs) differ from C-class flaring ARs remains unclear. Here, we calculate the key magnetic field parameters within the area of high photospheric free energy density (HED region) for 323 ARs (217 C- and 106 M$/$X-flaring ARs), including total photospheric free magnetic energy density E$_{free}$, total unsigned magnetic flux $\Phi$$_{HED}$, mean unsigned current helicity h$_{c}$, length of the polarity inversion lines $L$$_{PIL}$ with a steep horizontal magnetic gradient, etc., and compare these with flare/coronal mass ejection (CME) properties. We first show the quantitative relations among the flare intensity, the eruptive character and $\Phi$$_{HED}$. We reveal that $\Phi$$_{HED}$ is a measure for the GOES flux upper limit of the flares in a given region. For a given $\Phi$$_{HED}$, there exists the lower limit of F$_\mathrm{SXR}$ for eruptive flares. This means that only the relatively strong flares with the large fraction of energy release compared to the total free energy are likely to generate a CME. We also find that the combinations of E$_{free}$-$L$$_{PIL}$ and E$_{free}$-h$_{c}$ present a good ability to distinguish between C-class and M$/$X-class flaring ARs. Using determined critical values of E$_{free}$ and $L$$_{PIL}$, one predicts correctly 93 out of 106 M/X-class flaring ARs and 159/217 C-class flaring ARs. The large $L$$_{PIL}$ or h$_{c}$ for M$/$X-class flaring ARs probably implies the presence of a compact current with twisted magnetic fields winding about it., Comment: ApJ accepted for publication. 16 pages, 4 figures
- Published
- 2024