We've talked at length about the upcoming solar eclipse's potential effects here on the ground. But what about its impacts on Earth's atmosphere? During the total solar eclipse this April 8, NASA will launch three rockets aimed at understanding how a sudden reduction in sunlight affects the ionosphere. What NASA learns could help mitigate the radio and satellite communication errors known to occur during some eclipses.
Located within the thermosphere, Earth's ionosphere is what separates a majority of the planet's atmosphere from the vacuum of space. This sub-layer consists of gas particles that have been ionized—or electrically charged—by the Sun's radiation, hence its name. But because the Sun plays such a huge role in the ionosphere's structure, the sub-layer is known to change between day and night: The portion of the ionosphere that faces the Sun thickens as more particles are ionized, while the part experiencing night thins as ionized particles relax.
The regularity of Earth's day-night shift makes it somewhat easy for scientists to understand how the ionosphere fluctuates in a typical 24-hour period. But during a total solar eclipse, which essentially creates a short-term artificial night, the ionosphere's changes are a lot tougher to predict. This isn't just important for astronomy's sake; changes in the ionosphere tend to create radio and satellite communication errors, which can be anywhere from inconvenient to catastrophic for Earthly infrastructure or space operations.
That's where NASA's rockets come in. Sounding rockets, or recoverable suborbital rockets that carry research equipment, offer scientists a way to study the atmosphere without committing spacecraft to low Earth orbit. All three of NASA's Atmospheric Perturbations around Eclipse Path (APEP) sounding rockets were tested during the annular solar eclipse in October 2023, then recovered from New Mexico's White Sands National Park. Now, on April 8, they'll capture snapshots of the ionosphere before, during, and immediately after the total solar eclipse.
Just 45 minutes before the Moon slips in front of the Sun, NASA will launch one rocket from its Wallops Flight Facility in Virginia. From a maximum altitude of 260 miles (420 kilometers), the rocket will measure the density of charged versus neutral ionosphere particles, as well as the sub-layer's magnetic field. Four small secondary instruments launched from the rocket will duplicate each of the rocket's measurements to ensure accuracy. This process will occur all over again at the eclipse's peak, then once more 45 minutes after the peak has passed.
Though coastal Virginia will only get about 81% coverage during the eclipse's peak, the rockets launched from Wallops Island will likely capture invaluable data about the eclipse shadow's ionospheric perturbations. These insights could help prevent high-frequency communication issues later down the line.
