It is said that the farther away from the heat source, the cooler the air. Strangely, this is not the case with the sun. Now, New Zealand scientists may have figured out the key reason.
The surface temperature of the sun is about 6000 degrees Celsius, but within a few hundred kilometers from the surface of the sun, the temperature will suddenly rise to more than 1 million degrees Celsius, becoming the sun’s atmosphere, That is the corona.
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“The temperature is so high that the gas escapes the gravity of the sun and becomes the ‘solar wind’ , flying into space, crashing into Earth and other planets,” said study leader Dr Jonathan Squire from the University of Otago’s Department of Physics.
Researchers know from measurements and theory that the sudden increase in temperature is related to the magnetic field on the sun’s surface. But how these magnetic fields heat the gas is not yet known — a problem known as coronal heating.
“Astrophysicists have several different ideas about how magnetic field energy is converted into heat to explain this heating, but most have struggled to explain the observations certain aspects,” Squire said.
The prevailing theory is based on heating caused by turbulent flow, as well as heating caused by a type of magnetic wave called an ion cyclotron.
Squire and co-author Dr Romain Meyrand, in collaboration with scientists at Princeton University in the US and Oxford University in the UK, found that the two previous theories could be merged into one, solving a key part of the problem . The team’s findings were recently published in Nature Astronomy.
“However, both have some problems – turbulence is hard to explain why hydrogen, helium and oxygen in a gas get as hot as they are, while electrons are surprisingly cold; while magnetic wave theory could explain this feature, it doesn’t seem like there are enough waves on the surface of the sun to heat the gas,” Meyrand said.
The team used a six-dimensional supercomputer to simulate coronal gas, showing that the two theories are actually part of the same process, through a mechanism called a “spiral barrier.” Strange effects are linked.
This interesting phenomenon was discovered in earlier Otago research led by Meyrand.
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“If we imagine the plasma heating to happen as water running down a mountain, electrons are at the bottom is heated, then the spiral barrier acts like a dam, blocking the flow of water and converting its energy into ion cyclotron waves. In this way, the spiral barrier connects the two theories and solves their respective problems. ‘ Meyrand explained.
In this latest study, the team churned magnetic field lines in a simulation and found that the turbulence created waves, which then caused heating.
When this happens, the structures and eddies that form end up looking remarkably similar to measurements from NASA’s Parker Solar Probe, which recently became the first A man-made object that actually flew into the corona.
“This gives us the confidence to accurately capture key physical phenomena in the solar corona that, combined with theoretical discoveries about the heating mechanism, are a key tool in understanding coronal heating. Effective ways.”
Learning more about the Sun’s atmosphere and subsequent solar wind is important because of their profound effects on Earth, Squire explained.
The effect of the solar wind interacting with Earth’s magnetic field is known as “space weather,” and it causes everything from auroras to radiation that destroys satellites and geomagnetic currents that disrupt power grids . Fundamentally, these are triggered by the heating of the corona and its magnetic field.
“Perhaps, with a better understanding of fundamental physics, we can build better models to predict future space weather, and thus implement conservation strategies to avoid billions of dollar loss,” Squire said.
(Popular Science China)