An international team of researchers of Peking University, China; including one at Indian Institute of Astrophysics, Bengaluru, has unravelled why the Sun’s atmosphere is hotter than its surface.

About Corona’s Heating Puzzle

  • The temperature at the core of the Sun is nearly 15 million degrees Celsius, while that at its surface layer, known as the photosphere, is merely 5,700 degrees C. 
  • The natural thing to expect is that still further outwards, in its atmosphere, known as the corona, the temperatures would be comparable to that at the surface (photosphere).
  • But in reality the temperature of the corona is much higher. It starts increasing outside the photosphere, reaching a value of about one million degrees or more in the corona. 




Deciphering the puzzle

  • The key to the puzzle lies in geyser-like jets known as solar spicules that emanate from the interface of the corona and the photosphere. 
  • While in a photograph these look like tiny hairlike projections, they are in fact 200-500 kilometres wide and shoot up to heights of about 5,000 km above the solar surface.
  • It has been suspected that these spicules act as conduits through which mass and energy from the lower atmosphere bypass the photosphere and reach the corona.
  • The present study, has deciphered how these spicules form and also shows that they act as conduits through which hot plasma is carried into the corona region.