Explosions of plasma in the Sun's atmosphere can reach temperatures of nearly 100,000 °C, much hotter than scientists had expected.
The finding is one of several about the region between the solar surface and the uppermost edge of the Sun's atmosphere, or corona, revealed by NASA's Interface Region Imaging Spectrograph (IRIS) mission. The spacecraft (pictured before its launch) found that much of the energy from solar flares goes into heating and accelerating the plasma explosions, reports a team led by Hardi Peter of the Max Planck Institute for Solar System Research in Göttingen, Germany.
Viggo Hansteen of the University of Oslo and his co-workers found short loops of magnetized plasma that flicker out within minutes and could help to explain how the corona gets so hot.
Jets of charged particles less than 300 kilometres wide also occasionally appear for up to 80 seconds, and may fuel the solar wind, say Hui Tian of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and his colleagues.