The nonlinear evolution of electromagnetic instabilities in reversed shear plasmas is investigated by means of global gyrokinetic simulations. It is found that the kinetic infernal mode (KIM), which is a pressure-driven instability with low to intermediate toroidal mode number excited in a region of low magnetic shear, is unstable at high β, while the ion temperature gradient mode is unstable at low β, where β is the ratio of the plasma kinetic pressure to the magnetic pressure. The β threshold of the KIM is much lower than that of the kinetic ballooning mode (KBM) appearing in a normal shear plasma, while both the KIM and KBM are strong at the unfavorable curvature region, and the KIM has the same parity as the KBM. Nonlinear simulations show that the KIM gets saturated by exciting strong zonal flows and fluctuations of low toroidal mode number. The amplitude of the KIM turbulence is similar to that of the KBM turbulence in spite of the fact that the linear growth rate of the KIM is much higher than that of the KBM. This is because the excitation of zonal flows and fluctuations at low toroidal mode number is stronger in the reversed shear plasma than that of the normal shear plasma. On the other hand, the energy flux and particle flux due to the KIM turbulence are about two or three times larger than those by the KBM turbulence.

中文翻译：

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反向剪切托卡马克中动力学地狱模式的全局陀螺动力学非线性模拟

通过全局陀螺动力学模拟研究了反向剪切等离子体中电磁不稳定性的非线性演变。发现动力学地狱模式 (KIM) 是一种压力驱动的不稳定性，具有在低磁剪切区域激发的中低环形模式数，在高 β 时不稳定，而离子温度梯度模式在低 β，其中 β 是等离子体动压与磁压的比值。KIM 的 β 阈值远低于正常剪切等离子体中出现的动力学气球模态 (KBM)，而 KIM 和 KBM 在不利曲率区域都很强，并且 KIM 与 KBM 具有相同的奇偶性. 非线性模拟表明，KIM 因激发强烈的纬向流动和低环模数的波动而饱和。尽管 KIM 的线性增长率远高于 KBM，但 KIM 湍流的幅度与 KBM 湍流的幅度相似。这是因为在低环模数下的带状流动和波动的激发在反向剪切等离子体中比在正常剪切等离子体中更强。另一方面，KIM 湍流引起的能量通量和粒子通量大约是 KBM 湍流引起的能量通量和粒子通量的两倍或三倍。