Numerical Experiments Based on the Catastrophe Model of Solar Eruptions
Numerical Experiments Based on the Catastrophe Model of Solar Eruptions
复制标题
基于太阳喷发灾变模型的数值实验
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Jun Lin
中科院分区：
文献类型：
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作者：
Xiaoyan Xie;Udo Ziegler;Zhixing Mai;Ning Wu;Jun Lin
在Isenberg等人开发的突变模型的基础上，我们使用NIRVANA代码执行磁流体动力学（MHD）数值实验来研究日冕磁结构的各种行为，包括用于模拟日冕中悬浮的日珥的载流通量绳。这些行为包括磁通绳平衡高度随背景磁场变化的演化，相应的磁通绳内部平衡，系统失去平衡后磁通绳的动态特性，以及参考半径对磁通绳平衡高度的影响。在我们的计算中，我们使用了Sittler & Guhathakurta给出的日冕密度分布的经验模型，并考虑了物理扩散。我们的实验表明，平衡高度的模拟结果与理论结果存在偏差，但不明显，两种结果的演化特征相似。如果通量绳最初位于理论平衡曲线的稳定分支，由于系统的自我调节，在模拟中经过几轮振荡后，通量绳将迅速达到平衡位置；如果将磁通绳的初始位置设置在理论平衡曲线上的临界点处，则磁通绳将失去平衡。相应的，磁通绳的内部平衡也可以达到，由于我们的实验中提升了磁通绳小半径的近似，与理论结果有一定的偏差，但这种偏差并不影响系统的全局平衡。参考半径对助流绳平衡高度的影响与理论预测一致。我们的计算表明，失平衡后通量绳的运动与Lin-Forbes模型和观测预测的结果一致。实验中观察到磁通绳前方的快模激波的形成。磁通绳的向外运动是平滑的，由于计算中考虑了两种扩散，磁能连续地转换为其他类型的能量，并且允许磁通绳后面的电流片中依次发生磁重联。
On the basis of the catastrophe model developed by Isenberg et al., we use the NIRVANA code to perform the magnetohydrodynamics (MHD) numerical experiments to look into various behaviors of the coronal magnetic configuration that includes a current-carrying flux rope used to model the prominence levitating in the corona. These behaviors include the evolution in equilibrium heights of the flux rope versus the change in the background magnetic field, the corresponding internal equilibrium of the flux rope, dynamic properties of the flux rope after the system loses equilibrium, as well as the impact of the referential radius on the equilibrium heights of the flux rope. In our calculations, an empirical model of the coronal density distribution given by Sittler & Guhathakurta is used, and the physical diffusion is included. Our experiments show that the deviation of simulations in the equilibrium heights from the theoretical results exists, but is not apparent, and the evolutionary features of the two results are similar. If the flux rope is initially locate at the stable branch of the theoretical equilibrium curve, the flux rope will quickly reach the equilibrium position in the simulation after several rounds of oscillations as a result of the self-adjustment of the system; and the flux rope lose the equilibrium if the initial location of the flux rope is set at the critical point on the theoretical equilibrium curve. Correspondingly, the internal equilibrium of the flux rope can be reached as well, and the deviation from the theoretical results is somewhat apparent since the approximation of the small radius of the flux rope is lifted in our experiments, but such deviation does not affect the global equilibrium in the system. The impact of the referential radius on the equilibrium heights of the flux rope is consistent with the prediction of the theory. Our calculations indicate that the motion of the flux rope after the loss of equilibrium is consistent with which is predicted by the Lin-Forbes model and observations. Formation of the fast mode shock ahead of the flux rope is observed in our experiments. Outward motions of the flux rope are smooth, and magnetic energy is continuously converted into the other types of energy because both the diffusions are considered in calculations, and magnetic reconnection is allowed to occur successively in the current sheet behind the flux rope.