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

Ohio State University, The, Columbus OH

Investigators

Abstract

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.