According to a report from NASA’s Goddard Space Flight Center, scientists recently gathered strong evidence to explain what makes the sun’s outer atmosphere is so much hotter than its surface. The new observations are consistent with only one current theory: Nanoflares, a constant sprinkling of spontaneous bursts of heating, provide the mysterious extra heat.
This finding is based on a mere six minutes of data from one of NASA’s least expensive types of mission: A sounding rocket. The EUNIS mission – Extreme Ultraviolet Normal Incidence Spectrograph – launched on April 23, 2013, gathering data every 1.3 seconds to track the properties of material over a wide range of temperatures in the complex solar atmosphere.
On the sun’s visible surface, called the photosphere, it registers at 6,000 Kelvins, while the corona regularly reaches temperatures which are 300 times as hot.
“That’s a bit of a puzzle,” said Jeff Brosius, a space scientist at Catholic University in Washington, D.C., and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Things usually get cooler farther away from a hot source. When you’re roasting a marshmallow you move it closer to the fire to cook it, not farther away.”
Theories abound as to what mechanisms power these nanoflares, and scientists will continue to explore these ideas further, gathering additional observations as their tools and instruments improve.
Video of the EUNIS sounding rocket mission can be found here.