Observation of polar cap patches and calculation of gradient drift instability growth times: A Swarm case study
Observation of polar cap patches and calculation of gradient drift instability growth times: A Swarm case study
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极冠斑块的观察和梯度漂移不稳定性增长时间的计算：群体案例研究
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发表时间：
2014
期刊：
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通讯作者：
J. Moen
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作者：
A. Spicher;T. Cameron;E. Grono;K. Yakymenko;S. Buchert;L. Clausen;D. Knudsen;K. McWilliams;J. Moen
Swarm使命代表了一种强大的新工具，可用于调查极冠斑块和极冠内部的等离子体结构。在早期调试阶段，三颗Swarm卫星以珍珠串配置运行，使中午至午夜穿越极地。这提供了一个无与伦比的机会，研究梯度漂移不稳定性（GDI）过程中的潜在作用，极地冠补丁系统地计算GDI的增长时间，在他们的过境跨越极点从白天到晚上。在这项研究中，陡峭的千米级梯度作为初始结构出现，在大约90分钟的时间内持续存在，需要一个补丁穿过极冠。GDI的增长时间进行了计算，为选择的陡峭的密度梯度的昼侧和夜侧。数值范围从23秒到147秒，这与最近在尖点极光区的火箭测量结果一致，并为未来的研究提供了模板。生长时间的1分钟的顺序发现在白天和黑夜支持现有的观点，即GDI可能发挥主导作用，在产生无线电波闪烁的不规则性补丁过境极冠从白天到夜晚。
The Swarm mission represents a strong new tool to survey polar cap patches and plasma structuring inside the polar cap. In the early commissioning phase, the three Swarm satellites were operated in a pearls‐on‐a‐string configuration making noon‐midnight transpolar passes. This provides an unparalleled opportunity to examine the potential role of the gradient drift instability (GDI) process on polar cap patches by systematically calculating GDI growth times during their transit across the pole from day to night. Steep kilometer‐scale gradients appeared in this study as initial structures that persisted during the approximate 90 min it took a patch to cross the polar cap. The GDI growth times were calculated for a selection of the steep density gradients on both the dayside and the nightside. The values ranged from 23 s to 147 s, which is consistent with recent rocket measurements in the cusp auroral region and provides a template for future studies. Growth times of the order of 1 min found both on the dayside and on the nightside support the existing view that the GDI may play a dominant role in the generation of radio wave scintillation irregularities as the patches transit the polar cap from day to night.