One of the longstanding mysteries in solar physics is why the Sun's outer atmosphere, or corona, is millions of degrees hotter than its surface.
Now, scientists claim to have finally solved the mystery after they discovered a major source of hot gas that replenishes the corona -- jets of plasma shooting up from just above the Sun's surface, the 'Science' journal reported.
Scott McIntosh of the National Center for Atmospheric Research in Colorado, a member of an international team which carried out the NASA-supported research, said: "It's always been quite a puzzle to figure out why the Sun's atmosphere is hotter than its surface.
"By identifying that these jets insert heated plasma into the Sun's outer atmosphere, we can gain a much greater understanding of that region and possibly improve our knowledge of the Sun's subtle influence on the Earth's upper atmosphere."
Team member Rich Behnke of the National Science Foundation, which funded the research, said: "These observations are a significant step in understanding observed temperatures in the solar corona.
"They provide new insight about the energy output of the Sun and other stars. The results are also a great example of the power of collaboration among university, private industry and government scientists and organisations."
In fact, for its research, the team focused on jets of plasma known as spicules, which are fountains of plasma propelled upward from near the surface of the Sun into the outer atmosphere.