Ionospheric Response to the 2020 South American Total Solar Eclipse: Observing Atmospheric Gravity Waves and Total Electron Content Interactions

日全食一直是人们关注的最明显的天象。对于广泛的科学研究来说，这也是一个独特的机会。太阳辐射的突然关闭可能会在从地表到电离层的整个大气中造成扰动，电离层是地球表面上方约50至600英里处离子和自由电子高度集中的大气区域。观测日食期间的这种扰动为了解电离层动力学和大气层中的能量传输提供了一个独特的机会。这次2020年的南美日食特别令人感兴趣，因为它将发生在下面的安第斯山脉正在产生大气重力波(AGW)的区域，这会对电离层中的总电子含量(TEC)产生扰动。在这个项目中，该小组将对2020年12月智利南部和阿根廷日全食期间电离层中的总电子含量(TEC)和AGW之间的相互作用进行观测和建模。它将重点关注与安第斯山脉地形锋面相关并由其锚定的被称为“山波”的AGW。该小组将收集大约35个全球导航卫星系统(GNSS)站点的大地测量数据和6个站点在2020年日食之前、期间和之后的天气观测，以研究TEC被日食产生的AGW扰动的机制。现有稀疏全球导航卫星系统连续网络的站点将得到安装以观测日食的临时站点的补充。通过开发和应用新技术，该团队将分析产生的数据集，以解决有关电离层TEC变化和日食本影之间相互作用的悬而未决的问题。这些新的观测将使该团队能够在2017年和2019年日食期间收集的观测数据的基础上再接再厉。新的观测还将有助于完善数据处理技术和对未来日食的解释，例如2024年的北美日食。该项目将解决具体的科学问题：日食通过大气条件的变化，是否会引发山波或其他与地形特征有关的对流层水平的AGW？这些触发的AGW是否会传播到电离层的高度，从而扰乱电离层的TEC？日食是否像早先的理论研究预测的那样，触发了与地形无关的AGW？该团队将使用电离层动态3D模型(SAMI3)和奇异谱分析(SSA)这一非参数建模技术，将TEC扰动与受太阳遮挡影响的背景TEC分开。日食在全食区域内和周围产生了两组截然不同的TEC变化：一组是由于电离辐射的减少和关闭造成的直接影响，另一组是与大气和天气冷却有关的一组更复杂的间接影响，这些影响从基本的大气行为传播到电离层。由于目前TEC分析技术的局限性，与日食引起的AGW和电离层TEC之间的复杂相互作用有关的扰动了解得很少。该项目将通过收集新数据、将SSA等新技术应用于TEC时间序列和模拟AGW-TEC相互作用来处理这两个主题。该项目将有助于制作准确的背景TEC模型，以可靠地探测由海啸和核爆炸引发的AGW(以及声波)引起的电离层时间序列异常。它还将提高依赖于电离层实时状态的系统的可靠性，包括电信和实时定位服务。该项目将由一名职业生涯较早的阿根廷裔美国教员领导，并通过将一名拉丁美洲女大地测量员纳入实地工作和随后的数据分析，进一步促进地球科学的多样性。俄亥俄州立大学(OSU)的一名研究生将参与现场活动和对TEC数据的分析。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。

Total solar eclipse has always been the most visible celestial phenomenon that attracts public attention. It is also a unique opportunity for a broad range of scientific research. The sudden shutdown of solar radiation can create disturbances throughout the atmosphere, from the surface to the ionosphere, a region of atmosphere with a high concentration of ions and free electrons from about 50 to 600 miles above the Earth's surface. Observation of such disturbances during a solar eclipse provides a unique opportunity to understand ionospheric dynamics and energy transportation in the atmosphere. This 2020 South America solar eclipse is of particular interest because it will occur in a region where atmospheric gravity waves (AGWs) are being generated by the Andes below, which create perturbations in the total electron content (TEC) in the ionosphere. In this project the team will observe and model the interaction between the total electron content (TEC) in the ionosphere and AGWs during the December 2020 total solar eclipse in southern Chile and Argentina. It will focus on AGWs known as “mountain waves” that are associated with and anchored by the topographic front of the Andes. The team will collect geodetic data at about 35 Global Navigation Satellite System (GNSS) sites and weather observations at 6 sites before, during, and after the 2020 eclipse so as to examine the mechanisms by which TEC is perturbed by eclipse-generated AGWs. The sites of the existing sparse GNSS continuous network will be complemented with temporary sites installed to observe the eclipse. Through the development and application of novel techniques, the team will analyze the resulting dataset to address unresolved questions about interactions between the ionospheric TEC variations and the eclipse’s umbra. These new observations will allow the team to build on observational data collected during the 2017 and the 2019 eclipses. New observations will also help to perfect the data processing techniques and interpretation of future eclipses, such as the 2024 North American eclipse. This project will address specific scientific questions: does the passage of the eclipse, through changes in atmospheric conditions, trigger mountain waves or other troposphere-level AGW associated with topographic features? Do these triggered AGWs propagate up to ionospheric heights, perturbing the ionospheric TEC? Does the eclipse trigger AGWs not associated with topography, as predicted by earlier theoretical studies? The team will use a dynamic 3D model of the ionosphere (SAMI3) and singular spectrum analysis (SSA), a non-parametric modeling technique, to separate TEC perturbations from the background TEC affected by the obscuration of the Sun. Eclipses generate two sets of distinct TEC changes within and around the totality zone: a direct effect due to the reduction and shutoff of ionizing radiation, and a set of more complex indirect effects, associated with both cooling of the atmosphere and the weather, that propagate into the ionosphere from the underlying atmospheric behavior. Perturbations related to the complex interaction between eclipse-induced AGWs and the ionospheric TEC are poorly understood due to limitations in current TEC analysis techniques. This project will address both topics by collecting new data, applying new techniques such as SSA to TEC time series, and modeling the AGW-TEC interactions.The project will help to produce accurate background TEC models to reliably detect anomalies in ionospheric time series due to AGWs (and also acoustic waves) triggered by tsunamis and nuclear explosions. It will also enhance the reliability of systems that depend on the real-time state of the ionosphere, including telecommunications and real-time positioning services. The project will be led by an early career Argentine-American faculty member and further promote diversity in geosciences by including a female Latin American geodesist in fieldwork and subsequent data analysis. A graduate student from Ohio State University (OSU) will participate in the field campaign and the analysis of the TEC data.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.