The Great Solar Eclipse 2024: Science Experiments

On April 8, 2024, millions of people across North America looked up to witness a rare total solar eclipse. While the public enjoyed the spectacle, NASA and other research institutions were executing a series of high-stakes experiments. For scientists, this was not just a visual event. It was a unique opportunity to turn the sky into a natural laboratory. By “chasing” the moon’s shadow, researchers gathered critical data on the sun’s outer atmosphere and the Earth’s upper atmospheric layers that is impossible to collect at any other time.

Chasing the Shadow: The WB-57 High-Altitude Jets

One of the most ambitious projects involved literally chasing the eclipse to extend the observation time. NASA deployed its WB-57 high-altitude research aircraft to fly along the path of totality.

While an observer on the ground in Texas or Ohio might have experienced about four minutes of darkness, these jets move at 460 miles per hour. By flying in the same direction as the moon’s shadow, the pilots were able to extend the duration of totality to over six minutes. This extra time was crucial for the instruments onboard to capture high-resolution data.

Flying Above the Atmosphere

The WB-57s fly at an altitude of 50,000 feet. This offers two massive advantages over ground telescopes:

• Weather Independence: At 50,000 feet, the planes are well above any cloud cover that might ruin the view for ground observers.
• Clearer Images: By flying above most of Earth’s atmosphere, the cameras avoid the blurring effect caused by air turbulence. They also capture infrared light that is usually absorbed by atmospheric moisture before it reaches the ground.

The Instruments

These jets carried specific payloads to study the solar corona. One key instrument was a mid-wave infrared camera designed to photograph the dust ring around the sun and search for “Vulcanoids.” These are hypothetical asteroids thought to exist inside the orbit of Mercury. They are usually impossible to see due to the sun’s glare, but the eclipse provided a rare window to hunt for them.

The APEP Mission: Rockets into the Ionosphere

While the jets looked up at the sun, another NASA mission looked at how the sudden darkness affected Earth. This was the APEP mission (Atmospheric Perturbations around Eclipse Path).

NASA launched three sounding rockets from the Wallops Flight Facility in Virginia. The goal was to study the ionosphere, a layer of the Earth’s atmosphere roughly 55 to 310 miles up. This layer is electrified by solar radiation and is critical for radio communications and GPS systems.

The Launch Sequence

To understand the changes fully, the timing had to be precise. The rockets were launched in a specific sequence:

1. 45 minutes before peak eclipse: To establish a baseline of normal ionosphere conditions.
2. During the peak eclipse: To measure the immediate effects of the sudden loss of sunlight.
3. 45 minutes after peak eclipse: To see how quickly the ionosphere recovered.

Why the Ionosphere Matters

When the sun sets at night, the ionosphere thins out slowly. However, during an eclipse, the sunlight vanishes and returns rapidly. Scientists compare this to a boat moving through water. The boat creates a wake. Similarly, the eclipse creates a “wake” or ripple in the atmosphere. The APEP rockets measured charged particle density and electric and magnetic fields to understand how these disturbances affect satellite communications and radio waves.

Solving the Coronal Heating Mystery

The primary target for many of these experiments is the solar corona. This is the sun’s outer atmosphere, which appears as a pearly white halo during totality. A major question in astrophysics is the “coronal heating problem.”

The surface of the sun (the photosphere) is about 6,000 degrees Celsius. Logic suggests that as you move away from a heat source, it should get cooler. However, the corona is significantly hotter, reaching temperatures over 1 million degrees Celsius.

During the 2024 eclipse, NASA utilized the ACES (Airborne Coronal Emission Surveyor) experiment. Flown on a Gulfstream V aircraft, this instrument utilized a solar spectrometer to analyze the light coming from the corona. By looking at specific wavelengths of infrared light, scientists hope to identify the magnetic processes responsible for heating the corona to such extreme temperatures.

Citizen Science: The Eclipse Megamovie and SunSketcher

NASA also relied on a massive network of citizen scientists to gather data that a single agency could not collect alone.

• The Eclipse Megamovie: This project mobilized photographers along the entire path of totality to take images of the corona. By stitching these images together, researchers created a continuous movie of the eclipse as it moved across the continent. This allows them to track transient features in the corona, such as plasma jets, over a period of 90 minutes rather than just a few minutes.
• SunSketcher: This smartphone app was used by volunteers to time the exact moments the sun’s light disappeared and reappeared through the valleys of the moon (Baily’s Beads). Collecting this data from thousands of locations helps refine our understanding of the sun’s precise shape. The sun is not a perfect sphere; it is an oblate spheroid. Measuring its oblateness helps test theories of gravity and solar physics.

SuperDARN and Ham Radio

The study of the ionosphere extended beyond rockets. The Super Dual Auroral Radar Network (SuperDARN) is a collection of ground-based radars normally used to study auroras. During the eclipse, these radars bounced radio signals off the ionosphere to map changes in plasma density and wind speed in the upper atmosphere.

Simultaneously, the HamSCI project involved amateur radio operators (hams) across North America. They transmitted signals during the eclipse to test how the changing ionosphere altered signal propagation. Many operators reported that high-frequency bands, which usually work better at night, suddenly became active during the day as the moon’s shadow passed over.

Frequently Asked Questions

Why does NASA use planes instead of satellites for this? Satellites in orbit cannot always hold the specific position required to view an eclipse for an extended duration in the same way a plane flying within the atmosphere can. Furthermore, instruments on planes can be serviced, adjusted, or swapped out, whereas satellite hardware is fixed once launched.

What is the main goal of studying the solar corona? The main goals are to understand why the corona is much hotter than the sun’s surface and to study how solar wind is accelerated. Solar wind interacts with Earth’s magnetosphere and can cause space weather events that disrupt power grids and satellites.

Did the eclipse damage the ionosphere? No. The changes to the ionosphere are temporary. It is similar to the changes that happen every night when the sun sets, just much faster. The ionosphere returns to its normal state shortly after the sunlight returns.

How long will it take to analyze the data from 2024? While the event lasted only a few hours, the data analysis will take years. The images from the WB-57s and the data from the APEP rockets provide terabytes of information that scientists will be combing through for the next decade.