Collaborative Research: Anomalous Plasma Cooling in the Topside Ionosphere During Solar Eclipses

先前在2017年日食期间对上层大气（电离层）弱电离部分的观测揭示了一个令人惊讶的结果。两颗卫星在850千米高空穿越电离层顶层观测到的电子和离子温度，并不是预期的对月球阴影的平滑响应，而是在较冷的等离子体区域和正常温度区域之间显示出复杂和零星的跳跃。这个项目将通过对这次日食和其他日食事件的等离子体观测（温度、密度、流量）进行彻底的分析，来调查这些意想不到的等离子体温度调制。这将提供关于电离层如何响应照明驱动的瞬态变化的重要信息。了解这些反应是很重要的，因为太阳光照是电离和结构基本过程的关键驱动因素。通过电离层的无线电传播取决于电离和结构发生的程度，日食提供了一种受控和可量化的方式，可以更多地了解电离层对使用无线电频率的全球网络（例如全球导航卫星系统）的正面和负面影响。该项目将利用国防气象卫星计划对等离子体密度、电子和离子温度以及等离子体输运的测量，提供日食期间电离层等离子体异常的详细特征。它还将提供不规则太阳源区与相应的电离层瞬态调制之间相互关系的识别和表征。最后，该项目将确定异常流动和温度的物理机制，控制参数和限制情况。这项工作的最终目标是更好地理解白天电离层照明的短期变化如何在电离层密度、温度和漂移中产生不均匀的响应。该项目将通过支持波士顿大学的研究生，促进高技能劳动力的发展。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Previous observations during the 2017 solar eclipse in the weakly ionized portion of the upper atmosphere (the ionosphere) revealed a surprising result. Rather than the expected smooth response to the Moon's shadow, the electron and ion temperatures observed by two satellites traversing the topside ionosphere at 850 km in altitude showed complex and sporadic jumps between regions of cooler plasma and regions where the temperatures were nominal. This project will investigate these unexpected plasma temperature modulations by conducting a thorough analysis of the plasma observations (temperatures, density, flows) for this and other past eclipse events. This will provide important information about how the ionosphere responds to the transient changes in the illumination drivers. Knowledge of these responses is important since solar illumination is a key driver of fundamental processes of ionization and structuring. Radio propagation through the ionosphere depends on how much ionization and structuring occurs, and solar eclipses provide a controlled and quantifiable way to learn more about both positive and adverse effects of the ionosphere on global networks that use radio frequencies, for example the Global Navigation Satellite System. This project will provide detailed characterization of the ionospheric plasma anomalies during solar eclipses using Defense Meteorological Satellite Program measurements of the plasma density, electron and ion temperatures, and plasma transport. It will also provide identification and characterization of mutual relationship between the irregular solar source regions and consequential ionospheric transient modulation. Finally, the project will identify the physical mechanisms, controlling parameters, and limiting cases of the anomalous flows and temperatures. The ultimate goal of this work is to obtain a better understanding of how short-term changes in the illumination of the dayside ionosphere can produce non-uniform responses in the ionospheric density, temperature, and drifts.This project will contribute to the development of a highly-skilled workforce by supporting a graduate student at Boston University.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.