On April 8, 2024, a total solar eclipse will occur in parts of the United States, and NASA-funded experiments are set to investigate the effects of this celestial event on the ionosphere. The ionosphere, an electrically conductive layer of our atmosphere located 100 to 400 miles above the Earth’s surface, experiences amplified changes during a total solar eclipse.
The ionosphere plays a crucial role in long-distance AM and shortwave radio communication. Radio operators use this layer to extend their broadcast range by bouncing signals off the ionosphere and around the curvature of the Earth. It is sustained by the Sun, as its rays separate negatively charged electrons from atoms, creating positively charged ions. At night, the ions and electrons recombine into neutral atoms, causing a portion of the ionosphere to disappear. When dawn breaks, the electrons are freed again, and the ionosphere swells in the Sun’s illumination, creating a daily cycle.
A total solar eclipse presents a unique opportunity for scientists to observe a natural experiment in action. Three NASA-funded projects are focusing on studying the changes in the ionosphere during the upcoming eclipse.
The Super Dual Auroral Radar Network (SuperDARN) is a collection of radars located worldwide that bounce radio waves off the ionosphere to analyze the returning signal. During the 2024 eclipse, three U.S.-based SuperDARN radars will monitor changes in the ionosphere’s density, temperature, and movement. Led by Bharat Kunduri from Virginia Polytechnic Institute and State University, the team will compare SuperDARN’s measurements with computer models to understand how the ionosphere responds to a solar eclipse.
Another experiment, called Ham Radio Science Citizen Investigation (HamSCI), involves amateur or “ham” radio operators. These operators will attempt to send and receive signals before, during, and after the eclipse. Led by Nathaniel Frissell from the University of Scranton, the HamSCI project aims to catalog how the sudden loss of sunlight during totality affects radio signals. By comparing the results to previous eclipse observations and computer models, Frissell hopes to assess the widespread changes in the ionosphere.
The RadioJOVE project focuses on detecting radio signals from space, particularly from Jupiter. However, during the total solar eclipse, RadioJOVE participants will shift their attention to the Sun. Using radio antenna kits, they will record solar radio bursts before, during, and after the eclipse. During the 2017 eclipse, some participants observed a reduction in the intensity of solar radio bursts. Chuck Higgins from Middle Tennessee State University and a founding member of RadioJOVE emphasizes the importance of more observations to draw firm conclusions about radio propagation through the ionosphere.
These NASA-funded experiments offer valuable insights into the behavior of the ionosphere during a total solar eclipse. By studying the changes in density, temperature, movement, and radio signals, scientists hope to enhance our understanding of this enigmatic layer of our atmosphere. The data collected will contribute to improving computer models and expanding our knowledge of how the ionosphere responds to solar eclipses.