September 21, 2023

Why is the Sun’s outer atmosphere so staggeringly hot? AI can help us find out

    the face of the sun is obscured by the moon during an eclipse, revealing the wispy lines of the sun's outer atmosphere, or corona

the face of the sun is obscured by the moon during an eclipse, revealing the wispy lines of the sun’s outer atmosphere, or corona

Researchers are using artificial intelligence to solve a long-standing solar mystery.

At about 1.8 million degrees Fahrenheit (1 million degrees Celsius), the sun‘s outer atmosphere, or corona, is much hotter than its visible “surface,” the photosphere, which radiates hottest at 10,340 degrees F (5,730 degrees C). However, no one knows exactly why the corona is so hot.

There are two leading theories about the cause: heat released by dissipating plasma waves traveling through the corona, and energy released by breaking and reconnecting magnetic field lines. Both seem to be active on the sun, but what the dominant form of heating is, or whether they both contribute equally, remains unknown.

Related: The sun is erupting with a record number of sunspots, raising concerns about solar storms

Now researchers at Northumbria University in England are turning to artificial intelligence to help answer this question. In one project, Patrick Antolin and Ramada Sukarmadji teamed up with scientists at the Lockheed Martin Solar and Astrophysics Laboratory to use machine learning to hunt for tiny flares that release “nanojets” into the corona.

Nanoflares are an idea invented by solar physicist Eugene Parker (whose is NASA Parker solar probe is named after) in the late 1980s. He hypothesized that when magnetic field lines loop up and into the solar corona break and reconnect, they release a sudden burst of energy. In 2021, Antolin and other scientists observed using data from NASA’s Interface Region Imaging Spectrograph (IRIS) mission nanoflares For the first time. The question is, are they common enough to explain the warming of the corona?

Because they are small, nanoflares and the resulting nanojets of energy are difficult to detect.

“At the moment we can only identify nanojet events by eye, what we need is a way to detect them automatically,” Sukarmadji said in a statement. rack. “They are very small and the limited evidence we have suggests there are probably more of them than we think. But to really understand them further we need to be able to detect them when they occur.”

tendrils of orange plasma floating above the sun in close-up

tendrils of orange plasma floating above the sun in close-up


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By training AI algorithms to recognize nanojets in images from space missions such as IRIS, the Parker Solar Probe, NASA’s Solar Dynamics Observatory (SDO) and the European Space Agency Solar Orbiterthe team hopes to gain more insight into how common nanoflares occur.

Another side effect of magnetic reconnection in the corona sought by AI is a phenomenon called “coronal rainIt occurs when the reconnection causes localized drops in temperature in the corona. This forms denser clumps of plasma, some 150 miles (250 km) wide, and then falls out of the corona at 62 miles (100 km) per second, like gigantic falling stars. When they hit the photosphere, brief but brilliant flashes and shock waves can result, sending a wave of hot plasma back up toward the corona.

Antolin and fellow Northumbrian solar physicist Luke McMullan train AI on images of corona rain seen by IRIS, then use those algorithms to enhance lower-resolution images taken by SDO and search them for signs of corona rain.

Together, these two AI-led searches into the effects of magnetic reconnection could finally answer the question of why the solar corona is so incredibly hot.

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