arXiv 1708.045222017-08-15astro-ph.SR

观测驱动的太阳日冕模式中磁通量绳的识别和表征

Magnetic Flux Rope Identification and Characterization from Observationally-Driven Solar Coronal Models

Chris Lowder, Anthony Yeates

备注：: Accepted for publication in ApJ (16 pages, 14 figures, 2 tables, 2 animations)
DOI：: 10.3847/1538-4357/aa86b1

摘要：

磁通量是由日冕中的磁场剪切和重联作用形成的，是一种沿轴线缠绕的扭曲磁场结构。它们的演化和潜在爆发对空间天气具有重要意义。在这里，我们描述了一种新的方法，用于自动检测磁通绳在模拟磁场，基于磁力线螺旋度。比以前的方法更强大，它还允许确定每个磁通绳结构的全体积范围。我们的磁通绳检测和组织（FRoDO）代码是公开的，它可以测量喷发前磁通绳随时间的磁通量和螺旋度含量，并检测喷发。作为第一个演示，该代码被应用于从时间依赖的磁摩擦模型的输出，跨越1996年6月15日至2014年2月10日。在此期间，1561喷发和2099非喷发的磁通量绳检测，跟踪，并确定其特征。对于这个特定的模型数据，爆发通量绳有一个平均净螺旋度大小的$(2.66 \pm 6.82) \times 10^{43}$ Mx $^2$，而非爆发通量绳有一个显着较低的平均值$(4.04 \pm 9.25) \times 10^{42}$ Mx $^2$，虽然有重叠的两个分布。类似地，喷发通量绳的平均无符号磁通量为$(4.04 \pm 6.17) \times 10^{21}$ Mx，显著高于非喷发绳的平均值$(7.05 \pm 16.8) \times 10^{20}$ Mx。这些爆发通量绳的值是在广泛的范围内预期从观测和理论估计，虽然在这个特定的模型中的喷发率低于观测到的日冕物质抛射。在未来的FRoDO代码将被证明是一个有价值的工具，用于评估不同的非潜在日冕模拟的性能，并将它们与观测结果进行比较。

英文摘要：

Formed through magnetic field shearing and reconnection in the solar corona, magnetic flux ropes are structures of twisted magnetic field, threaded along an axis. Their evolution and potential eruption are of great importance for space weather. Here we describe a new methodology for the automated detection of flux ropes in simulated magnetic fields, based on fieldline helicity. More robust than previous methods, it also allows the full volume extent of each flux rope structure to be determined. Our Flux Rope Detection and Organization (FRoDO) code is publicly available, and measures the magnetic flux and helicity content of pre-erupting flux ropes over time, as well as detecting eruptions. As a first demonstration the code is applied to the output from a time-dependent magnetofrictional model, spanning 1996 June 15 - 2014 February 10. Over this period, 1561 erupting and 2099 non-erupting magnetic flux ropes are detected, tracked, and characterized. For this particular model data, erupting flux ropes have a mean net helicity magnitude of $(2.66 \pm 6.82) \times 10^{43}$ Mx$^2$, while non-erupting flux ropes have a significantly lower mean of $(4.04 \pm 9.25) \times 10^{42}$ Mx$^2$, although there is overlap between the two distributions. Similarly, the mean unsigned magnetic flux for erupting flux ropes is $(4.04 \pm 6.17) \times 10^{21}$ Mx, significantly higher than the mean value of $(7.05 \pm 16.8) \times 10^{20}$ Mx for non-erupting ropes. These values for erupting flux ropes are within the broad range expected from observational and theoretical estimates, although the eruption rate in this particular model is lower than that of observed coronal mass ejections. In future the FRoDO code will prove a valuable tool for assessing the performance of different non-potential coronal simulations and comparing them with observations.

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英文摘要：

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