论文标题
从无线性冠状模型中推论相对螺旋的可靠性
Deducing the reliability of relative helicities from nonlinear force-free coronal models
论文作者
论文摘要
我们研究了活性区域（AR）NOAA〜12673在十个小时的时间间隔内的相对螺旋性，该时间间隔围绕X2.2火炬（SOL2017-09-06T08：57），还包括爆发性的X9.3 flare（三个小时后发生）（SOL2017-09-06T11：SOL2017-09-06T11：53）。 In particular, we aim for a reliable estimate of the normalized self-helicity of the current-carrying magnetic field, the so-called helicity ratio $|H_{\mathrm{J}}|/|H_{\mathcal{V}}|$, a promising candidate to quantity the eruptive potential of solar ARs.使用SDO/HMI矢量磁场数据作为输入，我们使用优化方法采用非线性力（NLFF）冠状磁场模型。使用有限体积方法计算相应的相对螺旋性和相关数量。从基于自由模型参数的不同选择的多个时间序列中，我们能够评估$ | h _ {\ mathrm {j}}} |/| h _ {\ mathcal {v}} | $的差异，并估计其不确定性。与较早的作品相比，该作品确定了对总磁能的非甲状腺液贡献，$ e _ {\ rm div}/e $是有关随后的相对螺旋性分析的磁场模型所需的磁性磁铁质量的选择标准，我们建议使用除非固醇磁能，否则将使用磁场模型，除了对免费磁能的贡献，混合} |/e _ {\ mathrm {j，s}} $。作为对相对磁性螺旋性（和相关数量）的可靠估计的秘诀，我们建议使用基于自由模型参数的不同组合的多个NLFF模型，以保留那些表现出$ e _ {\ rm div}/e $和$ e $和$ | e _ {\ e _ {\ rm mix} $/e e _} |/e/e/e _ _ _ {瞬间，随后计算平均值估计值，并使用单独贡献值的扩散作为不确定性的指示。
We study the relative helicity of active region (AR) NOAA~12673 during a ten-hour time interval centered around a preceding X2.2 flare (SOL2017-09-06T08:57) and also including an eruptive X9.3 flare that occurred three hours later (SOL2017-09-06T11:53). In particular, we aim for a reliable estimate of the normalized self-helicity of the current-carrying magnetic field, the so-called helicity ratio $|H_{\mathrm{J}}|/|H_{\mathcal{V}}|$, a promising candidate to quantity the eruptive potential of solar ARs. Using SDO/HMI vector magnetic field data as an input, we employ nonlinear force-free (NLFF) coronal magnetic field models using an optimization approach. The corresponding relative helicity, and related quantities, are computed using a finite-volume method. From multiple time series of NLFF models based on different choices of free model parameters, we are able to assess the spread of $|H_{\mathrm{J}}|/|H_{\mathcal{V}}|$, and to estimate its uncertainty. In comparison to earlier works, which identified the non-solenoidal contribution to the total magnetic energy, $E_{\rm div}/E$, as selection criterion regarding the required solenoidal quality of magnetic field models for subsequent relative helicity analysis, we propose to use in addition the non-solenoidal contribution to the free magnetic energy, $|E_{\rm mix}|/E_{\mathrm{J,s}}$. As a recipe for a reliable estimate of the relative magnetic helicity (and related quantities), we recommend to employ multiple NLFF models based on different combinations of free model parameters, to retain only those that exhibit smallest values of both $E_{\rm div}/E$ and $|E_{\rm mix}|/E_{\mathrm{J,s}}$ at a certain time instant, to subsequently compute mean estimates, and to use the spread of the individually contributing values as an indication for the uncertainty.
