Scientists discovered an important clue while observing immense coils of hot, electrified gas, known as coronal loops. Scientists are interested in the corona, which appears as a halo of light seen by the unaided eye during a total solar eclipse, because eruptive events in this region can disrupt high-technology systems on Earth.
Astronomers also hope to use the solar corona studies to better understand other stars.
Aschwanden is lead author of a paper describing this research to be published in the Astrophysical Journal. The new observations reveal the location of the unidentified energy source, showing that most of the heating occurs low in the corona, within about 10,000 miles from the Sun's visible surface. The gas fountains form arches, hundreds of thousands of miles high, capable of surrounding 30 Earths. As gas emerges from the solar surface, it's heated and rises, then cools and crashes back to the surface at more than 60 miles per second. The old theory of uniform heating predicted that the loops would be substantially hotter at their tops because gas at the top of the loops is thinner, and does not radiate heat away as efficiently as the dense gas near the bottom.