Collaborative Research: CEDAR: Why is the High-Latitude Ionosphere More Variable in January than in July?

随着人类继续探索新的北极和南极的最后边界，极地国家投入巨资改善该地区的导航卫星覆盖。在这方面，极地纬度的高层大气（电离层）电离部分是这一难题的重要组成部分，因为它是卫星无线电信号传播的媒介，而且已知它含有强烈的干扰。该奖项为在极地纬度地区对意外的等离子体密度增强进行全面调查提供了支持，称为偶发性F。研究的重点是全球导航卫星系统（GNSS）的观测零星的F。导航卫星经常经历无线电信号质量的下降，并且零星的F已被证明是主要原因之一。随着冰盖融化北极向航运交通开放以及跨极飞行次数不断增加，这项调查特别及时，因为它有可能描述全球导航卫星系统信号丢失的发生情况并查明其机制。这项调查将验证最近的一组卫星观测结果，这些观测结果与传统智慧和过去基于几十年北方半球数据分析的预期背道而驰。验证将利用两个半球的地面观测和第一原理建模。众所周知，零星的F是由磁层强迫（对流和降水），它已被假设，热层的变化也可能是重要的。因此，人们期望对这些系统（磁层和热层）的特性有新的认识。为了帮助绘制和了解动态高纬度等离子体流，将使用和开发最先进的拉格朗日相干结构分析代码。这项工作有可能改变对一种现象的理解，这种现象自发现以来一直是广泛研究的主题。该奖项反映了NSF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。

With humanity continuing to explore last frontiers of the new Arctic and Antarctic, polar nations invest heavily in improving navigation satellite coverage of this region. In this context, the ionized portion of the upper atmosphere (ionosphere) at polar latitudes represents an important piece of the puzzle, since it is the medium through which the satellite radio signal travels and since it is known to contain strong disturbances. This award provides support for a comprehensive investigation into unexpected plasma density enhancements at polar latitudes called sporadic-F. The focus of the investigation is on the Global Navigation Satellite System (GNSS) observations of sporadic-F. Navigation satellites often experience degradation of radio signal quality and sporadic F has been demonstrated to be one of the leading causes. Opening of Arctic to shipping traffic as the ice cap melts and an ever-increasing number of transpolar flights make this investigation particularly timely due to its potential to characterize occurrence and identify mechanisms for GNSS signal loss. This investigation will validate a recent set of satellite observations that fly in the face of conventional wisdom and past expectations based on decades of northern hemisphere data analysis. The validation will utilize ground-based observations in both hemispheres and first-principles modeling. It is well-known that sporadic-F is controlled by magnetospheric forcings (convection and precipitation), and it has been hypothesized that thermospheric variations may also be important. Therefore, new insights into the characteristics of those systems (magnetosphere and thermosphere) are expected. To aid in mapping and understanding dynamic high-latitude plasma flows, the state-of-the-art Lagrangian coherent structure analysis code will be used and developed. This work has the potential to transform the understanding of a phenomenon that has been the subject of extensive study since its discovery.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.