模拟剪切电离层E × B流中梯度漂移或Kelvin-Helmholtz不稳定性的支配
Modeling the dominance of the gradient drift or Kelvin-Helmholtz instability in sheared ionospheric E x B flows
摘要：
研究表明，在非均匀电离层等离子体中的剪切$\mathbf{E}\times\mathbf{B}$流中，梯度漂移（GDI）或Kelvin-Helmholtz（KHI）不稳定性可能增长。这项工作研究的条件下，导致这些不稳定性之一，占主导地位的其他使用一种新的模式来研究本地化的电离层不稳定性。与中性粒子的碰撞效应在不稳定性发展中起着重要的作用。结果表明，在低碰撞度区，KHI占主导地位，在高碰撞度区，GDI占主导地位，并存在一个中间区域，其中两种不稳定性同时存在。对于低碰撞的情况下，其中的速度剪切是足够远的密度梯度，GDI被发现增长作为一个次要的不稳定性延伸的KHI涡。在速度切变的方向上包含中性风驱动的电场并不影响任一不稳定性的优势。利用经验电离层模式的数据，发现了两个高度极限，当高度超过上限时，KHI是主要的。对于低于下限的高度，GDI占主导地位。在中间区域，两种不稳定性一起增长。增加速度切变会使两个极限高度降低。这意味着，对于密度和速度梯度跨越很大高度范围的电离层现象，如极光下极化流，天基和地基观测仪器观测到的不稳定性可能有很大不同。
英文摘要：
Studies have shown that in sheared $\mathbf{E}\times\mathbf{B}$ flows in an inhomogeneous ionospheric plasma, the gradient drift (GDI) or the Kelvin-Helmholtz (KHI) instability may grow. This work examines the conditions that cause one of these instabilities to dominate over the other using a novel model to study localized ionospheric instabilities. The effect of collisions with neutral particles plays an important role in the instability development. It is found that the KHI is dominant in low collisionality regimes, the GDI is dominant in high collisionality regimes, and there exists an intermediate region in which both instabilities exist in tandem. For low collisionality cases in which the velocity shear is sufficiently far from the density gradient, the GDI is found to grow as a secondary instability extending from the KHI vortices. The inclusion of a neutral wind driven electric field in the direction of the velocity shear does not impact the dominance of either instability. Using data from empirical ionospheric models, two altitude limits are found. For altitudes above the higher limit, the KHI is dominant. For altitudes below the lower limit, the GDI is dominant. In the intermediate region, both instabilities grow together. Increasing the velocity shear causes both limits to be lower in altitude. This implies that for ionospheric phenomena whose density and velocity gradients span large altitude ranges, such as subauroral polarization streams, the instabilities observed by space-based and ground-based observation instruments could be significantly different.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
