We evaluate the validity of Nonlinear Force Free Field (NLFFF) reconstruction performed with Optimization class (OPTI) codes. We present a postprocessing method that removes the inevitable non-solenoidality of the magnetic field calculated by OPTI codes, which is caused by the noticeable role played by the gradient of the gas pressure in the force balance at photospheric heights, and by some of the mathematical properties of the optimization procedure and the associated boundary value problem (BVP). In essence, postprocessing converts the entire non-solenoidal part of the magnetic field into a solenoidal field, which possibly represents an actual deviation of the magnetic field from its force-free approximation in the photosphere and the corona. Two forms of postprocessing are analyzed in this paper. Postprocessing I eliminates the non-solenoidal component without changing the transverse field at the measurement level, and Postprocessing II leaves the normal field component unchanged. Magnetic field reconstruction, postprocessing, and the comparison of certain values and energy characteristics are performed for active region AR 11158 over a short part of its temporal evolution including the X-class flare in 2011 February. Our version of the OPTI code showed that the free energy decreased by ∼ 10 32 $\sim10^{32}$ erg within 1 hour, which corresponds to theoretical estimations of the flare-caused magnetic energy loss. This result differs significantly from the one in Sun et al. (Astrophys. J. 748 , 15, 2012 ). Therefore, we also comment on some features of our OPTI code, which may cause significant differences between our results and those obtained using the Wiegelmann (Solar Phys. 219 , 87, 2004 ) version of OPTI code in the study by Sun et al. (Astrophys. J. 748 , 15, 2012 ).

中文翻译：

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非线性无力场优化重建的有效性

我们评估使用优化类 (OPTI) 代码执行的非线性自由场 (NLFFF) 重建的有效性。我们提出了一种后处理方法，它消除了由 OPTI 代码计算出的磁场不可避免的非电磁性，这是由于光球高度力平衡中气压梯度所起的显着作用，以及一些数学公式引起的。优化程序的属性和相关的边界值问题 (BVP)。本质上，后处理将磁场的整个非螺线管部分转换为螺线管场，这可能代表了磁场与其在光球和日冕中的无力近似值的实际偏差。本文分析了两种后处理形式。后处理 I 消除了非电磁元件而不改变测量级别的横向场，后处理 II 保持正常场分量不变。对活动区域 AR 11158 进行了磁场重建、后处理以及某些值和能量特征的比较，在其短暂的时间演化过程中，包括 2011 年 2 月的 X 级耀斑。我们的 OPTI 代码版本表明，自由能在 1 小时内降低了 ∼ 10 32 $\sim10^{32}$ erg，这与耀斑引起的磁能损失的理论估计相对应。这一结果与 Sun 等人的结果显着不同。(Astrophys. J. 748, 15, 2012)。因此，我们也对我们的 OPTI 代码的一些特性进行了评论，这可能会导致我们的结果与在 Sun 等人的研究中使用 Wiegelmann (Solar Phys. 219, 87, 2004) 版本的 OPTI 代码获得的结果之间存在显着差异。(Astrophys. J. 748, 15, 2012)。