Magnetic waves may heat the corona

Growing evidence suggests that magnetic waves are the reason our star’s corona is so hot. 

Coronal hole

A close-up, false-color look at the Sun shows the large, dark polar coronal hole astronomers studied in order to determine what heats our star’s corona. White lines show the position of the Hinode spacecraft’s spectrometer slits, used to observe gas motions in the corona.
Courtesy Michael Hahn

Last week, while many of us were suffering from sweltering temperatures, solar physicists meeting in Bozeman, Montana, were discussing their own heat problem: the enduring mystery of why the Sun’s corona is roughly 100 times hotter than the layers below it.

A new analysis by Michael Hahn and Daniel Savin (Columbia University) suggests that astronomers might have the culprit in hand. This culprit, the so-called Alfvénic waves, has been a suspect for more than seven decades. The oscillations move along solar magnetic field lines like the vibrations in a plucked guitar string, and it’s thought that somehow they transfer their energy to the Sun’s hot, ionized gas. In 2011 the waves were detected permeating the upper solar atmosphere.

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