“Campfires” to heat the sun’s crown

AFP, Posted on Wednesday 05 May 2021 at 07:53

The abundance of “campfires” that heat the sun’s crown can explain why its temperature is higher than its surface, which is a real physical mystery as the solar orbiter tries to unravel.

To date, “we have no coherent explanation for this phenomenon,” Frederick Achere, an astronomer with the Astronomical Institute, told AFP.

This has been going on for more than 70 years, with the solar corona – the Sun’s atmosphere, whose white disk warming the Earth – surpassing the Sun’s surface temperature of one million degrees Celsius. About 5,500 degrees.

“When we move away from it, the temperature drops a little bit, and when we move away from it, like a radiator, it heats up a lot”, but very quickly this temperature rises very high, it appears in astronomy and astronomy.

This is where the solar orbiter comes into operation, according to a study by the European Space Agency and NASA, which took the first images of the sun last year. Five minute observation to check the proper functioning of his tools.

About 77 million kilometers from the Sun, halfway between the Earth and its star, they showed a new phenomenon: mini solar flares, ubiquitous on the surface, called “campfires”.

Since then, a team of European, American and Russian scientists has approached “clean” data that has been measured, that is, taken by an instrument of study that takes ultraviolet images.

Thanks to him, we were able to “see the finest structures in the atmosphere of the sun”, Mr. Achere explains, and to determine whether they are “small-scale copies of the big events we already know”.

400 to 4,000 km long (smaller than the size of the Sun), they rise 1,000 to 5,000 km above the Sun’s surface – the halo. Intermediate, they appear in very short periods of 10 to 200 seconds. But in this very short time the “coronal” temperature will reach over one million degrees Celsius.

Scientists consider this way to be “warming of the atmosphere by countless small flashes occurring everywhere,” said Ms. David Bergmans of the Royal Observatory in Belgium, who signed the study with David Long. Achere explains. , From the Mullard Space Science Laboratory, UK.

– “Matches” –

The second study, led by Chinese scientist Yazi Chen and Professor Hardy Peter from the German Max Planck Institute, designed the event using the observations of a solar orbiter.

He comes to a similar conclusion, suggesting that “this process contributes significantly to the heat of the crown.”

In short, “we are trying to heat up the atmosphere of this big star with competition”, in short, everyone adds that it is necessary to wait for other detailed observations to confirm a scene. Well m. Wow. Atmosphere that can rise millions of kilometers above the surface.

“We are trying to find out if these small explosions are enough and if they carry enough energy to bring the corona to its temperature,” he adds.

You have to handle yourself with a little patience. The solar orbiter will deploy all its capabilities in the fall, when the battery of its instruments is fully operational.

Through the Spice Spectrograph – Frederick Achere is the scientific director – we expect accurate measurements of the temperature and density of the solar atmosphere, so its campfire.

The PHI polarization draws intermediate “maps” of countless magnetic fields passing through its surface, and its contact is thought to be the driving force behind the campfire. These interactions are at the heart of large solar flares.

It is necessary to wait until next February-March, when the study will be twice as close as it was in the first column of the sun, where it will be even clearer, and especially smaller, at 200 km. . ‘Huh. Who knows, the smaller the fire, the more likely it is.

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