Density irregularities have been observed in subauroral polarization streams (SAPS). One hypothesis of the cause of this ionospheric turbulence, based on the background morphology, is the gradient drift instability (GDI). This work models the GDI using a two‐dimensional electrostatic fluid model to determine if it is a viable cause of turbulence generation in SAPS. A statistical study of different velocity profiles, based on SuperDARN radar and Global Positioning System total electron content data, is used to prescribe parameters in the numerical model. The parameter space of different SAPS profiles is explored to study the effect on GDI development. As the velocity shear is initialized closer to the unstable density gradient, the GDI becomes increasingly damped. For these cases, the density and electric potential turbulence cascades obtained from the numerical model follow power laws of about −5/3 or −2, which is in agreement with observational data. If the region of sheared velocity overlaps the density gradient, the GDI becomes stabilized. The latitudinal location of maximum GDI growth depends on the density profile, the velocity profile, and the neutral wind direction. Using velocity profiles with regions of low velocity shear can cause instabilities that grow inside SAPS which have turbulence cascades with different behavior. In all parameter regimes considered, the GDI turbulence is precluded from extending through regions of velocity shear. Turbulence is generated for a variety of SAPS relevant conditions; therefore, the GDI has been shown to be a viable candidate for generating ionospheric irregularities in SAPS.

中文翻译：

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梯度漂移的不稳定性是导致极光下极化流密度不规则的原因的研究

在耳下极化流（SAPS）中观察到密度不规则。基于背景形态，这种电离层湍流成因的一种假设是梯度漂移不稳定性（GDI）。这项工作使用二维静电流体模型对GDI进行建模，以确定它是否是SAPS中产生湍流的可行原因。基于SuperDARN雷达和全球定位系统总电子含量数据的不同速度剖面的统计研究，用于在数值模型中规定参数。探索了不同SAPS配置文件的参数空间，以研究其对GDI开发的影响。随着速度剪切被初始化为更接近不稳定的密度梯度，GDI变得越来越衰减。对于这些情况，从数值模型获得的密度和电势湍流级联遵循约-5/3或-2的幂定律，这与观测数据一致。如果剪切速度区域与密度梯度重叠，则GDI变得稳定。最大GDI增长的纬度位置取决于密度分布，速度分布和中性风向。在低速剪切区域中使用速度剖面可能会导致SAPS内部出现不稳定性，这些不稳定性具有具有不同行为的湍流级联。在考虑的所有参数范围中，都不允许GDI湍流延伸通过速度剪切区域。在各种与SAPS相关的条件下都会产生湍流。因此，GDI已被证明是在SAPS中产生电离层不规则现象的可行候选者。