旋转Z极简中的爆炸性喷发周期
Explosive eruption cycles in a rotating Z-pinch
AI总结：
该研究通过磁流体动力学方法揭示了Z极简中MHD屏障的亚稳态特性，展示了其在临界高度崩溃并重复重建的周期性行为，通过组合优化计算了能量释放过程。
摘要：
一种超音速剪切流沿着磁场线方向可以线性稳定受限磁流体动力学（MHD）等离子体中的陡峭压力梯度。在Z极简几何中，我们展示出这种传输屏障——我们称之为“MHD屏障”——类似于托卡马克装置的边缘平台，是亚稳态的，即对有限振幅的磁通管位移不稳定。我们模拟了加热和剪切的Z极简中MHD屏障的缓慢形成，当达到临界高度时，该屏障崩溃，将约1个数量级的受限热能排出。MHD屏障随后重建，这一过程重复，类似于核聚变实验中观察到的ELM周期。我们证明，亚稳态平衡的可用能量以及最能量有利的排出等离子体量可以通过磁通管交换的组合优化从第一原理计算得出。
英文摘要：
A transonic shear flow directed along magnetic field lines can linearly stabilize a steep pressure gradient in a confined magnetohydrodynamic (MHD) plasma. In Z-pinch geometry, we show that, like the edge pedestal in tokamak devices, this transport barrier -- which we call the ``MHD pedestal'' -- is metastable, i.e., unstable to finite-amplitude displacements of flux tubes. We simulate the slow formation of an MHD pedestal in a heated and sheared Z-pinch, which collapses on reaching a critical height, expelling an order-unity fraction of the confined thermal energy. The MHD pedestal then rebuilds and the process repeats, in a manner analogous to the ELM cycle seen in fusion experiments. We show that the available energy of the metastable equilibrium, and the most energetically favorable amount of ejected plasma, can be calculated from first principles via combinatorial optimization of flux-tube interchanges.
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