Turbulence-dominated Shock Waves: 2D Hybrid Kinetic Simulations
Turbulence-dominated Shock Waves: 2D Hybrid Kinetic Simulations
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DOI：
10.3847/1538-4357/ac4781
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
M. Nakanotani;G. Zank;L.-L. Zhao-L.
中科院分区：
文献类型：
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作者：
M. Nakanotani;G. Zank;L.-L. Zhao-L.
我们进行二维混合动力学模拟研究湍流与激波的相互作用。我们在上游注入无力磁场，使其对撕裂模不稳定性不稳定。磁场演变成湍流并与音速马赫数为2.4的激波相互作用。湍流特性，总的和归一化的剩余能量和归一化的交叉螺旋度，改变整个冲击波。而速度和磁场波动的能量主要是均匀分布上游，速度波动放大占主导地位的下游的冲击波。在激波处，磁场、速度和密度波动的湍流谱的振幅也增加，而它们的谱指数保持不变。我们比较了我们的结果与Zank等人。湍流传输模型在冲击波，并发现它提供了一个合理的解释跨冲击波的光谱变化。我们发现，粒子被有效地加速在冲击波前，和幂律谱形成下游。这可以通过扩散冲击加速来解释，其中粒子通过在冲击波的上游和下游散射来获得能量。加速粒子的轨迹表明，上游湍流起着粒子散射的作用。
We investigate the interaction of turbulence with shock waves by performing 2D hybrid kinetic simulations. We inject force-free magnetic fields upstream that are unstable to the tearing-mode instability. The magnetic fields evolve into turbulence and interact with a shock wave whose sonic Mach number is 2.4. Turbulence properties, the total and normalized residual energy and the normalized cross helicity, change across the shock wave. While the energy of velocity and magnetic fluctuations is mostly distributed equally upstream, the velocity fluctuations are amplified dominantly downstream of the shock wave. The amplitude of turbulence spectra for magnetic, velocity, and density fluctuations are also increased at the shock wave while their spectral index remains unchanged. We compare our results with the Zank et al. model of turbulence transmission across a shock, and find that it provides a reasonable explanation for the spectral change across the shock wave. We find that particles are efficiently accelerated at the shock front, and a power-law spectrum forms downstream. This can be explained by diffusive shock acceleration, in which particles gain energy by being scattered upstream and downstream of a shock wave. The trajectory of an accelerated particle suggests that upstream turbulence plays a role scattering of particles.