Nanoflares responsible for superhot corona of the Sun

The Sun’s corona is known to be very hot. In fact, it is actually much hotter than the Sun’s surface. But the reason why the corona, the Sun’s outer atmosphere, is extremely hot — several million degrees Kelvin — was not known. Now scientists have apparently found the answer: nanoflares.

August 15, 2009 04:23 pm | Updated December 04, 2021 11:46 pm IST - CHENNAI:

Scientists have found that nanoflares are responsible for the very high temperature of the Sun's corona.

Scientists have found that nanoflares are responsible for the very high temperature of the Sun's corona.

The Sun’s corona is known to be very hot. In fact, it is actually much hotter than the Sun’s surface. But the reason why the corona, the Sun’s outer atmosphere, is extremely hot — several million degrees Kelvin — was not known.

Scientists have apparently found the answer: nanoflares.

The very hot temperatures of the Sun were previously attributed by scientists to a steady-heating phenomenon. According to the steady-heating model, the coronal loop of a given length and temperature should in turn have a specific density. But measurements showed otherwise. The coronal loops have much higher density.

Until now scientists did not find evidence of nanoflares, though the bigger solar flares are well known and studied.

The NASA’s X-Ray Telescope and the Extreme-ultraviolet Imaging Spectrometer, which are on board Japan’s Hinode satellite have provided the first ever proof of nanoflares.

These two instruments were able to measure ultra-hot plasma of 10 million degree K and 5 million degree K respectively, notes >NASA

According to James Klimchuk, an astrophysicist at the >Goddard Space Flight Center’s Solar Physics Laboratory in Greenbelt Maryland, U.S., the very high temperature measured by the instruments can only be produced by “impulsive energy bursts” — the nanoflares.

Dr. Klimchuk presented his findings recently at the > International Astronomical Union general Assembly in Rio de Janeiro, Brazil.

The nanoflares begin to heat the coronal loop in a very strange way. And wherever the density of the loop is low, the brightness is less and vice versa. About one million degree K is sufficient enough to make the corona bright.

According to a theoretical model used by Dr. Klimchuk and his team, the coronal loop is a collection of 5 million -10 million degree K high-density low-brightness strands and one million degree K low-density but brighter strands.

“For the first time we have detected this 10 million degree K plasma, which can only be produced by the impulsive energy burst of nanoflares,” Dr. Klimchuk was quoted as saying in the NASA release.

0 / 0
Sign in to unlock member-only benefits!
  • Access 10 free stories every month
  • Save stories to read later
  • Access to comment on every story
  • Sign-up/manage your newsletter subscriptions with a single click
  • Get notified by email for early access to discounts & offers on our products
Sign in

Comments

Comments have to be in English, and in full sentences. They cannot be abusive or personal. Please abide by our community guidelines for posting your comments.

We have migrated to a new commenting platform. If you are already a registered user of The Hindu and logged in, you may continue to engage with our articles. If you do not have an account please register and login to post comments. Users can access their older comments by logging into their accounts on Vuukle.