Laminar and turbulent plasmoid ejection in a laboratory Parker Spiral current sheet
Laminar and turbulent plasmoid ejection in a laboratory Parker Spiral current sheet
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DOI：
10.1017/s0022377821000775
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发表时间：
2021-04
影响因子：
2.5
通讯作者：
E. Peterson;D. Endrizzi;M. Clark;J. Egedal;K. Flanagan;N. Loureiro;J. Milhone;J. Olson;C. Sovinec;J. Wallace;C. Forest
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文献类型：
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作者：
E. Peterson;D. Endrizzi;M. Clark;J. Egedal;K. Flanagan;N. Loureiro;J. Milhone;J. Olson;C. Sovinec;J. Wallace;C. Forest
在大红球上的实验以及用扩展磁流体动力学代码NIMROD进行的这些实验的模拟中，观察到磁流带结构尖端的准周期等离子体形成。在实验和模拟中发现，等离子体形成发生在一个依赖于压力梯度和磁曲率的特征时间尺度上。当压力梯度适中时，存在单模或层流等离子体，但当系统驱动较高时，会产生湍流等离子体喷射，从而产生多种尺寸的等离子体。然而，也观察到一个临界压力梯度，低于这个压力梯度等离子体流永远不会形成。一个简单的启发式模型，这种等离子体形成过程提出了一个结果，在高- $\beta$区域的头盔飘带的动态损失平衡。该模型能够解释实验和模拟中观测到的等离子体的周期性，当应用于高度为$3R_\odot$的太阳流光的二维模型时，产生的等离子体周期为90分钟。这与大角度和光谱日冕仪以及日地连线日冕和日球层调查仪器观测到的周期性等离子体斑点形成的位置和频率是一致的。
Quasi-periodic plasmoid formation at the tip of magnetic streamer structures is observed to occur in experiments on the Big Red Ball as well as in simulations of these experiments performed with the extended magnetohydrodynamics code, NIMROD. This plasmoid formation is found to occur on a characteristic time scale dependent on pressure gradients and magnetic curvature in both experiment and simulation. Single mode, or laminar, plasmoids exist when the pressure gradient is modest, but give way to turbulent plasmoid ejection when the system drive is higher, which produces plasmoids of many sizes. However, a critical pressure gradient is also observed, below which plasmoids are never formed. A simple heuristic model of this plasmoid formation process is presented and suggested to be a consequence of a dynamic loss of equilibrium in the high-$\beta$ region of the helmet streamer. This model is capable of explaining the periodicity of plasmoids observed in the experiment and simulations, and produces plasmoid periods of 90 minutes when applied to two-dimensional models of solar streamers with a height of $3R_\odot$. This is consistent with the location and frequency at which periodic plasma blobs have been observed to form by Large Angle and Spectrometric Coronograph and Sun Earth Connection Coronal and Heliospheric Investigation instruments.