活动区螺旋射流的数值模拟
Numerical Simulation of Helical Jets at Active Region Peripheries
摘要：
在整个日冕的少数极性侵入体上方观测到日冕喷流。一些最活跃的发生在活动区域的外围，那里的磁场强烈倾斜。这些喷流在低日冕中表现出非径向传播，因为它们遵循倾斜场，并且通常具有宽的螺旋形状。我们提出了一个三维磁流体动力学模拟这样的活动区周边螺旋喷流。我们考虑一个初始势场与双极磁通分布嵌入在一个高度倾斜的磁场，代表附近的活动区域的字段。少数极性的通量最初位于秃斑分界线之下。表面运动被用来将自由能注入分界线下方的封闭场中，形成S形通量绳，最终爆发产生螺旋状射流。我们发现，一个零点取代秃补丁早期的演变和喷发的结果从磁突破和一个理想的扭结喷发通量绳的组合。我们讨论了这两种机制是如何耦合的，并将我们的结果与以前的模拟冠孔射流。这种比较支持的假设，所有的日冕射流的通用机制是一个耦合之间的爆发重联和理想的不稳定性。我们进一步表明，我们的结果是在良好的定性和定量协议与活动区周边射流的观察。
英文摘要：
Coronal jets are observed above minority polarity intrusions throughout the solar corona. Some of the most energetic occur on the periphery of active regions where the magnetic field is strongly inclined. These jets exhibit a non-radial propagation in the low corona as they follow the inclined field, and often have a broad, helical shape. We present a three-dimensional magnetohydrodynamic simulation of such an active-region-periphery helical jet. We consider an initially potential field with a bipolar flux distribution embedded in a highly inclined magnetic field, representative of the field nearby an active region. The flux of the minority polarity sits below a bald-patch separatrix initially. Surface motions are used to inject free energy into the closed field beneath the separatrix, forming a sigmoidal flux rope which eventually erupts producing a helical jet. We find that a null point replaces the bald patch early in the evolution and that the eruption results from a combination of magnetic breakout and an ideal kinking of the erupting flux rope. We discuss how the two mechanisms are coupled, and compare our results with previous simulations of coronal-hole jets. This comparison supports the hypothesis that the generic mechanism for all coronal jets is a coupling between breakout reconnection and an ideal instability. We further show that our results are in good qualitative and quantitative agreement with observations of active-region periphery jets.
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