Scientists learn how sun transfers heat to the outer reachers of its atmosphere (4/6/2008)

The launch of EUNIS from White Sands Missile Range

As a result of intensive collaboration with NASA's Goddard Space Flight Center near Washington, astronomers at Queen's University Belfast have announced an exciting discovery that could pave the way to solving a problem which has been baffling solar physicists for years.

The fact that the temperature increases as you move away from the surface of the Sun has had scientists perplexed for decades. Many believe that waves travel from the surface of the Sun and release their energy in the outer layers of the solar atmosphere; similar to ocean waves travelling across the sea before releasing their energy when they crash into land.

Researchers from the Astrophysics Research Centre at Queen's and NASA have now shown that certain types of waves are unable to travel to the outer reaches of the Sun.

The discovery came after the use of compact and lightweight components allowed for the highly sensitive Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) to be launched from White Sands Missile Range in New Mexico.

During this NASA rocket flight, an unprecedented 145 spectral images of the outer atmosphere of our Sun were captured in under six minutes. Traditionally, such pictures taken by satellites would run at one per minute, while EUNIS provided images at a rate of one per 2.5 seconds at a massively lower cost.

David Jess, a current PhD student at Queen's University Belfast, has used the data from this flight to investigate processes occurring within our Sun's atmosphere.

"The sun is the building block of our lives. We rely on it for heat, light and so much more. Common sense tells us that the further you travel away from a heat source, the cooler the air will be. The Sun, however, doesn't obey common sense. The fact that the temperature increases as you move away from the surface of the Sun has been baffling solar physicists for decades. EUNIS has allowed us to test mechanisms for heat transfer to these outer reaches of the Sun's atmosphere," explained David Jess.

"Using the unrivalled data rates provided by EUNIS, we have shown that certain waves appear to hit a barrier at approximately 3000 km above the surface of the Sun, in a region called the corona. The corona can be seen during total eclipses. The amount of material, or density, at this height drops dramatically and we have revealed that this is the most likely cause for the dip in strength of the waves," according to Jess.

The Queen's University Solar Physics Group, led by Dr. Mihalis Mathioudakis, has been at the forefront of rapid wave observations in the Sun for many years.

"This is an amazing discovery as we try to aim to raise the understanding of waves in our Sun and finally comprehend why the outer layers of the Sun are hotter than its surface. The involvement of our group with NASA is providing a huge impact on the solar physics community." said Dr. Mathioudakis.

"Queen's University will be key players in a future flight of EUNIS scheduled for mid-2010."

EUNIS is currently undergoing extensive modifications at NASA's Goddard Space Flight Center to improve sensitivity and resolution for the 2010 launch.

Note: This story has been adapted from a news release issued by Queen's University Belfast

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