So this might be why the sun is so hot

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Aug 4, 2017

We know the sun is immensely, insanely, unfathomably hot, or else NASA would have long since sent a probe over there—but nobody is entirely sure why our star’s atmosphere is hundreds of times hotter than its comparatively cool but still blistering surface.

Think 6,000 degrees Fahrenheit when “cool” describes the sun. Multiply that by several hundred and you have a corona that burns at millions of degrees.

Now a team of scientists from UCL, George Mason University and Naval Research Laboratory who recently published a NASA-funded study in Nature Communications are thinking that the sun’s corona (atmosphere) scorches like the fires of Mount Doom because its elemental composition and magnetic activity are conspiring. Sort of.  The research shed light on how more magnetic activity in the solar corona is related to a boost in elements such as iron, which could have a significant effect on the skyrocketing of already torrid temperatures.

"Why the Sun's corona is so hot is a long-standing puzzle. It's as if a flame were coming out of an ice cube,” said team lead Dr. David H. Brooks of George Mason University. It doesn't make any sense! Solar astronomers think that the key lies in the magnetic field, but there are still arguments about the details.”

Just think, this is the corona at a time of low activity.

The sun has an 11-year magnetic cycle, during which conditions change from one extreme to the other. Mild periods at solar minimum eventually flare into a solar maximum with magnetic activity so intense that it leads to an increase in sunspots (evidence of magnetic field flux) on the photosphere and sends radiation levels soaring.

"Previously, many astronomers thought that elemental composition in a star's atmosphere depended on the properties of the star that don't change, such as the rotation rate or surface gravity,” said Dr. Brooks. “Our results suggest that it may also be linked with the magnetic activity and heating processes in the atmosphere itself, and they change with time, at least in the Sun."

Mass and energy that flow from a star’s photosphere (surface) into its corona are believed to be influenced by elemental composition. Some force that is still unknown transports certain elements into the corona over others, giving it a unique elemental signature. Any change in the amounts of these elements also means a change in mass and energy. If science can find out what this mysterious force is, it could unlock major insight into the transport of energy to the corona.

Until NASA finally does launch its solar probe, which could possibly give us even more answers, the team will continue to observe star cycles that could illuminate even more about why stellar coronae are the dragon's breath of space.

(via Phys.org)