This is one of the highest-resolution images ever taken of the solar corona, or outer atmosphere. It was captured by NASA’s High Resolution Coronal Imager, or Hi-C, in the ultraviolet wavelength of 19.3 nanometers. Hi-C showed that the Sun is dynamic, with magnetic fields constantly warping, twisting, and colliding in bursts of energy. Added together, those energy bursts can boost the temperature of the corona to 7 million degrees Fahrenheit when the Sun is particularly active. Credit: NASA

The Puzzle of Why the Sun is Hotter Away From Its Surface

Source: Harvard-Smithsonian Center for Astrophysics press release
Posted: 01/28/13

Summary: Solar astronomers have long wondered why the Sun’s atmosphere gets hotter, rather than colder, as you move away from the star’s surface. High resolution observations are now revealing the mechanism that pumps energy into the Sun’s corona.

The Sun’s visible surface, or photosphere, is 10,000 degrees Fahrenheit. As you move outward from it, you pass through a tenuous layer of hot, ionized gas or plasma called the corona. The corona is familiar to anyone who has seen a total solar eclipse, since it glimmers ghostly white around the hidden Sun.

But how can the solar atmosphere get hotter, rather than colder, the farther you go from the Sun’s surface? This mystery has puzzled solar astronomers for decades. A suborbital rocket mission that launched in July 2012 has just provided a major piece of the puzzle.

The High-resolution Coronal Imager, or Hi-C, revealed one of the mechanisms that pumps energy into the corona, heating it to temperatures up to 7 million degrees F. The secret is a complex process known as magnetic reconnection.

Read more: The Puzzle of Why the Sun is Hotter Away From Its Surface — Astrobiology Magazine.

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