One of the conundrums in solar physics was the question of why the chronosphere and solar wind regions of the sun were so very much hotter than the surface. The surface of the sun is typically around 5k kelvin while the outer regions have temps that spike well into the millions.
A long suspected magnetic field – plasma interaction has been confirmed according to published reports:
“…Magnetic waves — called Alfven waves — can carry enough energy from the sun’s active surface to heat its atmosphere, or corona.
‘The surface and corona are chock full of these things, and they’re very energetic,’ said Bart de Pontieu, a physicist at the Lockheed Martin Solar and Astrophysics Laboratory in California.
The sun contains powerful heating and magnetic forces which drive the temperature to tens of thousands of degrees at the surface — yet the quieter corona wreathing the sun reaches temperatures of millions of degrees. Scientists have speculated that Alfven waves act as energy conveyor belts to heat the sun’s atmosphere, but lacked the observational evidence to prove their theories.
De Pontieu and his colleagues changed that by using the Japanese orbiting solar observatory Hinode to peer at the region sandwiched between the sun’s surface and corona, called the chromosphere. Not only did they spot many Alfven waves, but they also estimated the waves carried more than enough energy to sustain the corona’s temperatures as well as to power the solar wind (charged particles that constantly stream out from the sun) to speeds of nearly 1 million mph.”
So cool to see the mechanism finally revealed. I remember this being one of the first big unanswered questions we’d come across when I was teaching astro courses at Lehigh. (We did solar astronomy before starting the stellar.)
Read the rest here.