NASA – Paola Testa led team of the Harvard-Smithsonian Centre for Astrophysics (CfA) has found new clues to the mystery of coronal heating using observations from the recently launched Interface Region Imaging Spectrograph (IRIS).The team found that miniature solar flares called “nanoflares” – and the speedy electrons they produce – might partly be the source of that heat, at least in some of the hottest parts of the Sun’s corona.

A solar flare occurs when a patch of the Sun brightens dramatically at all wavelengths of light. During flares, solar plasma is heated to tens of millions of degrees in a matter of seconds or minutes.

IRIS probe of the world’s premier space agency has been used to observe ‘bombs’ of plasma on the sun, nanoflares that rapidly accelerate particles, and powerful jets that could drive the solar wind, and some other phenomena, five new studies report.

The NASA spacecraft has been designed to enter planetary atmospheres but it cannot fly through the outer atmosphere of the sun, where temperatures reach 3.5 million degrees Fahrenheit (2 million degrees Celsius). 

The IRIS will have to study the star from a safe distance. IRIS is better than previous instruments and it can take far more detailed observations of the sun and can capture observations of regions only about 150 miles (240 kilometers) wide on a time scale of just a few seconds.

“The combination of enhanced spatial and spectral resolution, which are both three to four times better than previous instruments, allows a much closer look at the sun’s atmosphere,” Hardi Peter of the Max Planck Institute for Solar System Research in Germany told Peter was the lead author on a study of hot plasma ‘bombs’ on the sun.

The surface of the sun, or photosphere, is visible to human eyes.

The hotter chromosphere and transition regions are situated above the photosphere and these regions which emit ultraviolet light that can only be observed from space. This is because the atmosphere of the Earth absorbs most of this radiation before it reaches land-based instruments. The outer part of the solar atmosphere is called the corona.

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