Effect of Magnetic Storm Related Thermospheric Changes on the Evolution of Equatorial Plasma Bubbles
Effect of Magnetic Storm Related Thermospheric Changes on the Evolution of Equatorial Plasma Bubbles
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DOI：
10.1029/2018ja025995
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
A. Bhattacharyya;M. Fedrizzi;T. Fuller‐Rowell;P. Gurram;B. Kakad;S. Sripathi;S. Sunda
中科院分区：
文献类型：
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作者：
A. Bhattacharyya;M. Fedrizzi;T. Fuller‐Rowell;P. Gurram;B. Kakad;S. Sripathi;S. Sunda
过去预测赤道和低纬度站记录的 VHF 和 L 波段无线电信号闪烁的努力主要基于日落后赤道 F 层底部瑞利-泰勒不稳定性的理论线性增长率，该层负责产生赤道等离子体气泡（EPB）。然而，正是 EPB 在其非线性演化阶段达到倾角赤道上方的最大高度以及 EPB 内中等尺度不规则性的发展决定了闪烁的纬度分布。 VHF 和 L 波段接收器网络在安静的一天（2015 年 3 月 13 日和 2015 年 3 月 20 日，即 2015 年 3 月 17 日磁暴发生几天后）记录的闪烁幅度表明，3 月 20 日由 EPB 不规则性引起的闪烁的纬度范围小于 3 月 13 日。来自赤道站的地磁和电离探空仪数据以及从全球导航卫星系统观测获得的垂直总电子含量分布表明，这两天的赤道电离层条件大致相同。使用耦合热层、电离层、等离子体层和电动力学模型对这 2 天的热层条件进行了模拟。研究发现，2015 年 3 月 17 日的主要磁暴过后，热层原子氧密度增强，导致 3 月 20 日倾角赤道上空的离子-中性碰撞频率增强。这限制了这一天 EPB 在倾角赤道上升的高度，从而影响闪烁的纬度分布。
Past efforts to predict scintillations on VHF and L‐band radio signals recorded at equatorial and low‐latitude stations have been mostly based on a theoretical linear growth rate of Rayleigh‐Taylor instability on the bottomside of the post‐sunset equatorial F layer, which is responsible for the generation of an equatorial plasma bubble (EPB). However, it is the maximum height that an EPB reaches above the dip equator and development of intermediate scale irregularities within the EPB, in its nonlinear phase of evolution that determines the latitudinal distribution of scintillations. Amplitude scintillations recorded by a network of VHF and L‐band receivers on a quiet day, 13 March 2015 and on 20 March 2015, a few days after the 17 March 2015 magnetic storm, show that latitudinal extent of scintillations caused by EPB irregularities is lesser on 20 March than on 13 March. Geomagnetic and ionosonde data from an equatorial station, and vertical total electron content distributions obtained from Global Navigation Satellite Systems observations, indicate that the equatorial ionospheric conditions are approximately same on these 2 days. Simulation of thermospheric conditions for these 2 days is carried out using the Coupled Thermosphere, Ionosphere, Plasmasphere, and Electrodynamics model. It is found that thermospheric atomic oxygen density is enhanced in the aftermath of the major magnetic storm of 17 March 2015, resulting in enhanced ion‐neutral collision frequencies over the dip equator on 20 March. This limits the height to which an EPB rises over the dip equator on this day, and thus impacts the latitudinal distribution of scintillations.