NASA gets a quick glimpse of a mysterious layer of the sun

Imagine for a minute you’ve been transported into the middle layers of the sun’s atmosphere. The surface of the sun, the “visible disk” scientists call the photosphere, tip below you, red-hot plasma heated to 10,000 degrees Fahrenheit. Above you, the vast corona, an atmospheric aura of gas superheated to several million degrees Fahrenheit, projects heat, light, magnetism, and radioactive particles into space with explosive force. The crown has long been a puzzle to scientists: it is much hotter than the layers below. Traveling outward from the surface of the sun would be like stepping away from a campfire and feeling even more heat than when you were sitting next to the flames.

You float in the chromosphere, the slice of the sun’s atmosphere sandwiched between these two well-studied layers, which is named (“color sphere”) for its touches of pink visible from Earth during total solar eclipses. Up close, these pink lightning bolts are seas of boiling hydrogen plasma heading toward the massive horizon of the sun. But another, more dominant force is unleashed in the chromosphere: the sun’s magnetic fields. These fields are created well below the surface of the sun by the dynamo effect – heat and rotation on the largest scale of the solar system. The sun’s magnetic fields are massive, but in its inner layers their forces are channeled and controlled by the pressure of superheated plasma, convecting its heat outward like a boiling pot of tomato soup.

Put on your ultraviolet light glasses, however, and you’ll see something interesting. As it ascends into the chromosphere, the relative strength of the superheated plasma decreases rapidly, but the magnetic fields remain relatively strong. The higher you look, the more the forces of magnetism dominate. In the photosphere, magnetic fields push the plasma aside, exploding outward in massive loops, rooted at their base in dark regions we call sunspots. (In the photosphere, each is the size of the Earth.) These magnetic loops twist and shear as they interact with the plasma and with each other, creating a dynamic and chaotic environment – a superheated hubbub so powerful that the effects are felt. feel on our own planet 93 million kilometers away.

What you would see in the sun’s atmosphere is hypothetical, of course – not only because the chromosphere would instantly vaporize you, but because for decades scientists have had to guess exactly what’s going on inside. Unlike the photosphere and the crown, it is very difficult to see and therefore to map. “It’s a really confusing place,” says David McKenzie, principal investigator of NASA’s Chromospheric Layer Spectropolarimeter 2, or Clasp2, a sounding rocket that briefly fired above Earth’s atmosphere to observe the sun, then parachuted its payload of instruments and data. . “That’s what makes him so exciting. It is a border right in the middle of the atmosphere of the sun.

McKenzie is the co-author of a new article that appeared in February in Scientific progress, the result of data collected by Clasp2 in 2019, which represents the first successful mapping of the magnetic field of the four-layer chromosphere, using new techniques of ultraviolet imaging of a solar magnetic field. Written by a team from Japan, Europe and the United States, its results seem to confirm theories about how the crown gets overheated. Using these new mapping techniques, scientists believe they will be able to better understand in real time coronal mass ejections (CMEs) and “space weather” launched by the sun – huge magnetic and radioactive fields that cause chaos when they strike Earth. or technology in space.

Courtesy of David E. McKenzie

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