Abstract

The results of numerical calculations of the spatial distribution of increments of gradient-drift instability in the region of developed multiple equatorial ionospheric bubbles are presented. The results of the numerical modeling of the spatial structure of equatorial ionospheric bubbles and the measurement data in the areas of developed plasma bubbles, both satellite and terrestrial, show the presence in these areas of large electron density gradients reaching values ranging from 10⁻⁴ to 10⁻³ m⁻¹ and high drift transfer velocities exceeding 1000 m/s. With such plasma parameters, small-scale inhomogeneities can develop in the region of plasma bubbles, which increase due to various types of instabilities at positive growth rates. The spatial distribution of the gradient-drift instability increment is studied. With this type of instability, small-scale electron density inhomogeneities can be generated, whose spatiotemporal scales are characteristic of equatorial F-scattering. Due to the developed plasma bubbles on the fronts of which gradient-drift instabilities develop, the study is carried out in the approximation of a strong elongation of plasma bubbles along the geomagnetic field lines. This makes it possible to use the results of the numerical simulation of the instability using the two-dimensional approximation of the Rayleigh–Taylor instability model as the background electron concentration. Unlike the previous works of the authors, this study is aimed at obtaining the spatial distribution of the growth rate both for different configurations of plasma bubbles and for different ratios of wave numbers. When studying the features of the distribution of the increment of the gradient-drift instability in the region of the development of plasma bubbles, it is necessary to take into account the significant inhomogeneity of the background values of the electron density and drift velocities. In this study, this is achieved by comparing the wavelengths with the parameters of the zones of development of these waves; in particular, the spatial and temporal extent of the region of large positive values of the increase increment is estimated. These estimates determine the choice of the range of wave numbers. It is found that electron density gradients at the fronts of the developed ionospheric bubbles can be an effective mechanism for the development of a gradient-drift instability; the increment of gradient-drift instability at the fronts of plasma bubbles reaches 0.01 s^–1, and for multiple bubbles these values are slightly less than for a single bubble. Taking into account the time of the existence of regions with such increments of more than 1000 s, such values create the conditions for the development of small-scale inhomogeneities on the “legs” of the plasma bubbles.

中文翻译：

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多等离子体气泡条件下梯度漂移不稳定性参数的测定

摘要

给出了多个赤道电离层气泡发育区域梯度漂移不稳定性增量空间分布的数值计算结果。赤道电离层气泡空间结构的数值模拟结果以及卫星和地面等离子气泡发达区域的测量数据表明，这些区域存在大的电子密度梯度，达到10 ^-4至10 ⁻³  m ⁻¹以及超过 1000 m/s 的高漂移传输速度。有了这样的等离子体参数，等离子体气泡区域就会出现小规模的不均匀性，这种不均匀性会由于正增长率下各种类型的不稳定性而增加。研究了梯度漂移不稳定增量的空间分布。由于这种不稳定性，会产生小尺度的电子密度不均匀性，其时空尺度是赤道 F 散射的特征。由于等离子体气泡的前沿发展了梯度漂移不稳定性，因此该研究是在等离子体气泡沿着地磁场线的强烈伸长的近似值中进行的。这使得可以使用瑞利-泰勒不稳定性模型的二维近似作为背景电子浓度对不稳定性进行数值模拟的结果。与作者之前的工作不同，这项研究的目的是获得不同等离子体气泡配置和不同波数比率的增长率的空间分布。在研究等离子体气泡发展区域梯度漂移不稳定性增量的分布特征时，需要考虑电子密度和漂移速度背景值的显着不均匀性。在这项研究中，这是通过将波长与这些波的发展区域的参数进行比较来实现的；尤其，估计增加增量的大正值区域的空间和时间范围。这些估计决定了波数范围的选择。研究发现，发达的电离层气泡前端的电子密度梯度可能是梯度漂移不稳定性发展的有效机制；等离子体气泡前沿梯度漂移不稳定性增量达到0.01 s 研究发现，发达的电离层气泡前端的电子密度梯度可能是梯度漂移不稳定性发展的有效机制；等离子体气泡前沿梯度漂移不稳定性增量达到0.01 s 研究发现，发达的电离层气泡前端的电子密度梯度可能是梯度漂移不稳定性发展的有效机制；等离子体气泡前沿梯度漂移不稳定性增量达到0.01 s^–1，对于多个气泡，这些值略小于单个气泡。考虑到这种增量超过 1000 秒的区域的存在时间，这些值为等离子体气泡“腿”上小规模不均匀性的发展创造了条件。