How Earth's Sun's Atmosphere is Hotter Than Its Blazing Core

Two missions have taken a large step forward when it comes to understanding a bit more about the sun. Scientists have found a bit more about the corona and why it's hundreds of times hotter than the lower photosphere, which is the sun's visible surface.

In this latest study, the researchers observed a long-hypothesized mechanism for coronal heating, in which magnetic waves are converted into heat energy. Past papers have suggested that magnetic waves in the sun, called Alfvenic waves, have enough energy to heat up the corona. The question, though, is how that energy is converted to heat.

"For over 30 years scientists hypothesized a mechanism for how these waves heat the plasma," said Patrick Antolin, one of the researchers, in a news release. "An essential part of this process is called resonant absorption-and we have now directly observed resonant absorption for the first time."

Resonant absorption is a wave process in which repeated waves add energy to the solar material, a charged gas known as plasma, the same way that a perfectly-timed repeated push on a swing can make it go higher. Resonant absorption has signatures that can be seen in material moving side to side and front to back.

In order to see the full range of motions, the researchers used observations from NASA's Interface Region Imaging Spectrograph, or IRIS, and the Japan Aerospace Exploration Agency (JAXA)/NASA's Hinode solar observatory to successfully identify signatures of the process.

"Through numerical simulations, we show that the observed characteristic motion matches well what is expected from resonant absorption," said Antolin.

The findings are published in The Astrophysical Journal.

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