Why is the sun’s core cooler than its crust?

[karthick]

Why is the sun’s core cooler than its crust?

Why is our sun’s outer crust some 200-300 times hotter than its core? One lot of astrophysicists claimed to have the answer last year. But now another group says the first lot got it all wrong, leaving the paradox unexplained.

The sun’s core is about 6,000 degrees Celsius, but its outer layer, the corona, is far hotter. It’s a phenomenon that influences solar weather forecasting and the theory behind fusion reactors.

Last year American scientists said they had solved the mystery with research showing how high-energy Alfvén wave structures could super-heat the corona.

This seemed to be confirmed by astrophysicists who said they had detected Alfvén waves in the corona. They had published their results in prestigious journal Science.

Now, however, scientists at the University of Warwick say these waves are well-known magneto-acoustic kink waves - not Alfvén waves. These, they say, are a better fit as an explanation for the complex magnetic fields of the sun’s outer layer.

The latest findings have been published Thursday in the Astrophysical Journal Letters.

Said Warwick astrophysicist Tom Van Doorsselaere: “We interpret the data differently. They think they’re looking at an Alfvén wave, but in fact they are looking at kink waves.

“Kink waves are a bending of the magnetic field, much alike the bending of the string, when playing the guitar.

“Moreover, because the scientists from Boulder Colorado identified the wrong kind of wave all of their subsequent calculations are out. And, sadly, it means the question of why the corona is hot remains unanswered.”