Sun has always remained a mysterious celestial body for the global space experts. Now a group of scientists have successfully decoded why the Sun’s million-degree corona (the outermost atmosphere) is hotter than its surface.
The hotness of corona has been baffling the astronomers for decades. Finally, the team of researchers led by Paola Testa of the Harvard-Smithsonian Centre for Astrophysics (CfA) has uncovered new clues to this mystery.
The scientists used the observations made by the recently launched Interface Region Imaging Spectrograph (IRIS) to decode the mystery of coronal heating.
Sun’s corona layer possesses the miniature solar flares known as “nanoflares” along with the speedy electrons produced by them. According to the research team, the nanoflares and the electrons may partly be the source of the heat, at least at some of the hottest regions of corona.
Solar flares are also responsible for triggering electrons as well as protons from the solar plasma to a large fraction of the light’s speed. A solar flare occurs when a Sun’s patch brightens at all wavelengths of light. Scientists said at the time of flares, the solar plasma heats up to tens of millions of degrees in just seconds or minutes.
According to Testa, IRIS provides a new mode to carry observation on the telltale signs of nanoflares by having a close insight at the footpoints of coronal loops, i.e. loops of hot plasma extending from the surface of the Sun out into the corona.
The presence of high-energy electrons was inferred by the team using IRIS high-resolution ultraviolet imaging and spectroscopic observations of the footpoint brightenings.
With the help of computer simulations, the researchers modelled the response of the solar plasma that was confined in loops to the energy transported by energetic electrons.
The computer simulations showed that energy probably was deposited by electrons that traveled at the pace of about 20 percent of the speed of light.
The findings were reported in the journal Science.