标题： 临界环面不稳定性高度如何随太阳周期变化？ 显示英文标题

标题： How does the critical torus instability height vary with the solar cycle?

摘要： 理想磁流体动力学环面不稳定性可以驱动日冕物质抛射的爆发。 磁场强度衰减的临界阈值在不同太阳活动区域的不同高度发生，因此理解这种变化可能改善空间天气预测。 在这项工作中，我们旨在找出临界环面不稳定性高度如何在整个太阳活动周期中演变。 我们研究了1996年至2023年的HMI和MDI空间天气HMI活跃区补丁（SHARPs和SMARPs）的一个重要子集，总共包含来自4436个独特活跃区补丁的21584张磁图。 对于每张磁图，我们计算主要极性倒转线上的平均临界高度、总无符号磁通量以及正负磁极之间的分离度。 我们发现活跃区中的临界高度随着太阳活动周期变化，在太阳极大期（极小期）观察到较高的（较低的）平均临界高度。 我们得出结论，这是因为临界高度与相反磁极之间的分离度成正比，而这种分离度又与区域内的总磁通量成正比，太阳极大期观测到的磁力更强、通量更大且尺寸更大的区域更多。 这一结果值得注意，因为尽管临界高度更高，但在太阳极大期观测到的CMEs比太阳极小期更多。 显示英文摘要

摘要： The ideal magnetohydrodynamic torus instability can drive the eruption of coronal mass ejections. The critical threshold of magnetic field strength decay for the onset of the torus instability occurs at different heights in different solar active regions, and understanding this variation could therefore improve space weather prediction. In this work, we aim to find out how the critical torus instability height evolves throughout the solar activity cycle. We study a significant subset of HMI and MDI Space-Weather HMI Active Region Patches (SHARPs and SMARPs) from 1996-2023, totalling 21584 magnetograms from 4436 unique active region patches. For each magnetogram, we compute the critical height averaged across the main polarity inversion line, the total unsigned magnetic flux and the separation between the positive and negative magnetic polarities. We find the critical height in active regions varies with the solar cycle, with higher (lower) average critical heights observed around solar maximum (minimum). We conclude this is because the critical height is proportional to the separation between opposite magnetic polarities, which in turn is proportional to the total magnetic flux in a region, and more magnetic regions with larger fluxes and larger sizes are observed at solar maximum. This result is noteworthy because, despite the higher critical heights, more CMEs are observed around solar maximum than at solar minimum.