A year after the solar eclipse, Dallas area scientists are still uncovering cosmic clues

For some Dallas-area scientists, the total solar eclipse on April 8, 2024, was more than just a once-in-a-lifetime cosmic spectacle: It was a rare and invaluable research opportunity, the perfect controlled experiment.

Now, one year later, some researchers have begun to share their findings, while others are still piecing together data from those fleeting four minutes when the moon eclipsed the sun.

From the corona to the ionosphere

At Southern Methodist University, geophysicist Stephen Arrowsmith set up barometers across campus to measure changes in atmospheric pressure. He also parked a giant subwoofer playing inaudible, low-frequency chirps across the university.

The goal was to detect gravity waves—ripples in Earth’s atmosphere due to gravity pushing down on parcels of rising air—by detecting any changes as a sound travels. (Gravity waves aren’t to be confused with gravitational waves, invisible ripples in space-time.)

“The best analogy I have [of a gravity wave] is like a ship going over the ocean, producing this wave behind it,” said Arrowsmith, who is also a professor of earth sciences at SMU. “It’s kind of like that in the atmosphere, but it’s produced in the wake that’s generated by the eclipse itself.”

Eclipses have long been suspected to cause gravity waves, Arrowsmith added. Some studies have confirmed they do, but none so far have been based on data collected during a total solar eclipse, at least to his knowledge.

At the University of Texas at Arlington, professor of space physics Yue Deng seized the rare opportunity to study the sun’s corona. This glowing crown of plasma flares from the sun’s outer atmosphere becomes visible to the naked eye only during an eclipse’s fleeting shadow.

While the sun is about 93 million miles from Earth, its corona still manages to touch the planet. It does so through solar winds—a constant stream of charged subatomic particles hurled into space by the corona’s intense heat. These winds brush against Earth’s magnetic field and upper atmosphere, which help shield the planet from cosmic rays originating elsewhere in the galaxy. But solar winds can also disrupt telecommunications and endanger astronauts, especially during solar storms that blast out bursts of radiation.

The atmospheric disturbances triggered by the eclipse could interfere with radio signals and potentially lead to communication problems, wrote Deng in an email: “The eclipse provides us an excellent opportunity to study what happens when there is a sudden and localized change in the upper atmosphere.”

On the morning of the total solar eclipse, Deng and colleagues from UTA and the Massachusetts Institute of Technology set up instruments at the university’s Maverick Stadium. The researchers had cameras taking pictures of the corona and GPS receivers measuring total electron content, or the total number of electrons on the path between a radio transmitter and receiver. They also had magnetometers measuring changes in Earth’s magnetic field.

In Richardson, at the University of Texas at Dallas, Fabiano Rodrigues and his colleagues tracked changes in geospace, the combined area of Earth’s upper atmosphere and nearby space that also contains the ionosphere located some 50 to 400 miles above the planet’s surface.

The ionosphere is home to all of Earth’s charged subatomic particles in its atmosphere. It’s also the highway through which radio waves and GPS signals travel, pinging off gas particles and stray electrons en route to trackers and iPhones.

Throughout the day, the ionosphere is constantly shifting, going from energized by sunlight to falling into a stupor by nightfall. The quantity and motion of these charged particles is also impacted by Earth and space weather.

Rodrigues sought to create a sensor device that can provide real-time information on the dance of these particles in the ionosphere at a fraction of the cost of a commercial device, which typically runs in the tens of thousands of dollars, and without ever having to leave the ground.

He and his colleagues placed these sensors on UT Dallas’ campus and two locations in Dallas. They also placed them at colleges in New Hampshire, Pennsylvania, Illinois and Texas near or in the path of totality.

Some answers, more yet to come

All three D-FW area scientists are still working through the data they’ve collected. For Arrowsmith, the results so far are promising.

“We have this amazing set of observations,” Arrowsmith said, noting that they observed changes in the atmosphere. “We see changes in how long it’s taking sound to propagate around campus; those changes are happening really fast, and they’re happening all the time through the eclipse.”

The changes don’t match up perfectly with the change in temperature, which dropped about 3.3 degrees Fahrenheit during totality (or when the moon completely blocked the sun), according to the National Weather Service in Fort Worth. This observation seems to indicate that sound waves weren’t just traveling horizontally along the ground—think an invisible slinky moving on its side—but vertically, as if the slinky were upright and bouncing up into the air.

“[Sound] is traveling up into the atmosphere at slightly higher altitudes,” Arrowsmith said. “Not super high, but a few hundred meters or so and being refracted back to the ground.”

Arrowsmith is hopeful the research will prove useful for better weather prediction of short-term, small-scale weather phenomena. It may also have applications in understanding how sound travels through a city and related issues like noise pollution.

“There’s a lot of interest in being able to predict sound in urban environments,” Arrowsmith said, noting military applications such as predicting the size and location of an explosion.

“Understanding how sound travels in urban environments is actually of interest just in and of itself, also from a noise pollution angle to being able to understand these things better,” he added.

Deng’s data has confirmed a cooling effect in Earth’s upper atmosphere that moves with the eclipse’s path of totality—like a supersonic wave, she said. Scientists had observed this before, but the total solar eclipse made the connection much clearer.

But the data still leaves questions about a key driver of space weather: coronal mass ejections. These powerful outbursts of magnetized plasma erupt from the sun with varying frequency throughout its 11-year solar cycle—ranging from about once a week to several times a day at the peak of the solar cycle, according to NASA.

When these ejections slam into Earth’s magnetic field and upper atmosphere, they trigger intense geomagnetic storms tied to dazzling auroras. But beyond their beauty, coronal mass ejections can wreak havoc on satellites in low Earth orbit, temporarily knocking out critical navigation and communications systems.

“The thing we don’t know is when and how a coronal mass ejection will happen,” Deng said in a video call. “We just don’t know when a major [coronal mass ejection] can happen and cause a major storm. Even if a [coronal mass ejection] happens, it may or may not impact Earth.”

Rodrigues hopes his research will shed light on the ionosphere’s inner workings and help improve the accuracy of future radio and GPS systems that pass through it.

During the eclipse, he said, all his sensors made successful observations, proving the effectiveness of the technology. He added that his team is still working on an analysis of the data.

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