UH scientists map
sun’s outer magnetism

University of Hawaii solar scientists for the first time have mapped the magnetic field in the sun's outer atmosphere with a unique telescope that they built at Haleakala on Maui.

This development will help tremendously to understand the sun's effects on earth, astronomer Haosheng Lin said in a telephone interview from Denver. The scientists presented their findings at an American Astronomical Society meeting there today.

Lin, lead author of the study, worked with astronomer Jeff Kuhn, head of the Institute for Astronomy solar program at Haleakala, and engineer Roy Coulter on the telescope experiment.

The magnetic field is the most important field in the corona, Lin said, adding that it dominates everything and determines whether geomagnetic storms or solar flares evolve.

It has been known for years that magnetic fields control the outer parts of the sun that influence the earth's nearby space and upper atmospheric environment, the scientists said.

They are responsible for nearly all of the sun's explosive activities, causing variations in the amount and kinds of solar radiation that affects the earth's magnetosphere, ionosphere and its climate, they said. But while these magnetic fields have been measured on the visible surface of the sun, scientists weren't able until now to observe them through the corona, the faint outer region of the sun's atmosphere, Lin said.

Now that the magnetic field can be mapped, he said, "We can start to observe the source of the phenomena, which will give us a better handle to attack this problem."

The technology wasn't there to make observations of the sun's coronal magnetic fields until the UH group built a special telescope and instruments, he said.

During an eclipse, the moon blocks the light of the sun so the corona, a million times thinner than the light of the sun's disc, can be seen, Lin noted.

With their telescope, he said, "We are creating an artificial eclipse so you can see the corona that you can't see with a regular telescope."

He said they began developing the telescope and instruments to go with it four years ago with Coulter as the primary technician.

IFA Director Rolf Kudritzki said Haleakala's clear observing conditions helped to make the "exciting results" possible. "The ability to finally see the sun's coronal magnetic fields will open new opportunities for solar and solar-terrestrial research," he said.

Lin said the next step is to generate coronal magnetograms, or magnetic maps, that modelers can use "to improve our sketchy understanding of how the corona works.

"What we will do is start to make regular observations and try to catch the magnetic field in those regions that have flares," he said. "We want to catch them in action to see how the magnetic field evolves, how flares happen."

He said their unusual telescope "is only a small start." It's only half a meter inside but a bigger one can be built with the same design, he said.

"With this success, I think we can say we can do this. We need better resolution and better sensitivity, which requires a bigger telescope. Four meters would be great but we may want to go for two meters."

NASA, the National Science Foundation and the Air Force Office of Scientific Research supported the experiment.


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