Science can now explain why sun’s atmosphere is hotter than its surface

August 2, 2014

Researchers have found substantial evidence to explain why the Sun’s outer atmosphere is much hotter than its surface.
As per scientists, ‘Nanoflares’ – a continuous infusion of impulsive bursts of heating, none of which can be individually detected – is behind the production of the extra heat.
The photosphere, the visible surface of the Sun, is around 6,000 Kelvins, while the corona reaches temperatures which are 300 times more than the photosphere.
NASA’s EUNIS (Extreme Ultraviolet Normal Incidence Spectrograph) rocket, equipped with a very sensitive spectrograph gathered information about the Sun about how much material is present at a given temperature by recording different wavelengths of light.
EUNIS flew up nearly 321 km above the ground aboard a sounding rocket and gathered about collected observations from above the planet’s air.
It scanned a region on the Sun known to be magnetically complex, also termed active region, which can often be the source of larger flares and coronal mass ejections.
Several theories have been offered for how the magnetic energy coursing through the corona is converted into the heat that raises the temperature.
The EUNIS spectrograph was tuned into a range of wavelengths useful for locating material at temperatures of 10 million Kelvin – temperatures that are a key characteristic of nanoflares.
Scientists have conjectured that infinite number of nanoflares could heat up solar material in the atmosphere to temperatures of up to 10 million Kelvins. This material would cool very rapidly, producing ample solar material at the 1 to 3 million degrees regularly seen in the corona. However, the faint presence of that extremely hot material should remain.
The EUNIS team studied the data from the rocket and found a wavelength of light indicating presence of 10 million degree material.