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

之前在2017年日食期间在高层大气电离层(电离层)弱电离部分进行的观测显示了一个令人惊讶的结果。两颗卫星穿越海拔850公里的电离层顶部，观测到的电子和离子温度并没有对月球阴影做出预期的平稳反应，而是在较冷的等离子体区域和名义温度区域之间出现了复杂和零星的跳跃。这个项目将通过对这次和其他过去日食事件的等离子体观测(温度、密度、流动)进行彻底的分析，来研究这些意想不到的等离子体温度调制。这将提供有关电离层如何响应照明驱动器中的瞬时变化的重要信息。了解这些响应很重要，因为太阳照明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的发生程度，日食提供了一种可控和可量化的方式，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积极和不利影响。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传输的测量，详细描述日食期间的电离层等离子体异常。它还将确定和描述不规则太阳源区与相应的电离层瞬变调制之间的相互关系。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了解日侧电离层照度的短期变化如何在电离层密度、温度和漂移中产生非均匀响应。该项目将通过支持波士顿大学的一名研究生来促进高技能劳动力的发展。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.