Europe 1 with AFP 3:23 p.m., April 4, 2024

This is a scientific event rare enough to be highlighted. On April 8, thanks to a perfect alignment of the Moon with the Earth and the Sun, a total eclipse of the Sun will be visible in North America. This will be an exceptional opportunity for researchers to study certain scientific data. 

Millions of Americans will be able to observe a total eclipse on Monday, a rare phenomenon that will attract many tourists along a diagonal crossing the United States from south to northeast. This event, which will also be broadcast live on the internet, will be an incredible scientific opportunity for researchers.

Strange animal behaviors, a rarely observable solar corona, and even possible effects on humans: scientists will be hard at work on April 8 to collect valuable data during the solar eclipse. 

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A solar crown 

When the Moon completely covers the Sun's central disk, the outer layer of its atmosphere, called the solar corona, will be visible "in a very special way," said Pam Melroy, associate administrator at NASA. However, this is an area “that we do not yet fully understand”. The heat of the corona increases with distance from the surface of the Sun, a counterintuitive phenomenon that scientists struggle to explain. It is also in this upper region that solar flares occur, or the prominences of immense plasma structures.

During an eclipse, the lowest part of the corona is better visible than using a specific instrument called a coronagraph, says Shannon Schmoll, an astronomer at Michigan State University. So this is a golden opportunity to study it. One thing particularly excites scientists: the Sun is currently close to its peak activity, which returns every 11 years. Thus, “the chances of observing something incredible are very high,” rejoiced Pam Melroy.

What are the consequences for the Earth’s atmosphere? 

Scientists will also study changes in the upper part of Earth's atmosphere, the ionosphere. This is where a large part of the communications signals pass. “Disruptions in this layer can cause problems for our GPS and communications,” said NASA official Kelly Korreck.

However, the ionosphere is affected by the Sun: its particles are charged with electricity under its radiation during the day. Three small sounding rockets will be launched before, during and just after the eclipse from Virginia, in the eastern United States, in order to measure these changes.

The drop in light caused by the eclipse, more rapid and localized than a sunset, should make it possible to learn more about how light affects the ionosphere -- in order to be able to better predict potential future problematic disturbances.

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A surprising reaction in animals

Eclipses cause surprising behaviors in animals: for example, giraffes have been seen galloping, or roosters and locusts starting to crow. In addition to light, temperatures and winds can also drop, to which animals are sensitive.

Andrew Farnsworth, a researcher at Cornell University's Ornithology Laboratory, studies the effect on birds. It uses weather radars to detect animals in flight. During the previous eclipse in the United States, in August 2017, researchers observed “a drop in the number of flying animals,” he explains.

This eclipse had caused the cessation of daytime behavior (with insects or birds landing), but without causing nocturnal behavior such as the flight of bats or migratory birds, he explains. This year, in April, these birds may be further pushed to migrate. These studies are “important for understanding the way in which animals perceive the world”, underlines the expert.