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Hawaii News

University of Hawaii researchers measure sun’s powerful magnetic field

Researchers at the University of Hawaii have recently focused on an exotic area of the sun called the corona, and have shed light on the sun’s powerful magnetic field.

This work has implications on Earth. The so-called solar wind — fast-moving, high-energy particles — whack Earth’s magnetic field and periodically produce power outages.

UH Institute for Astronomy graduate student Benjamin Boe conducted a new study that used total solar eclipse observations to measure the shape of the coronal magnetic field with higher spatial resolution and over a larger area than ever before. The results were published June 3 in the Astrophysical Journal.

Boe was advised by UH-Manoa astronomy professor Shadia Habbal, who has led a group of eclipse chasers, the Solar Wind Sherpas, making scientific observations during solar eclipses for more than 20 years. These observations have led to breakthroughs in unveiling some of the secrets of the physical processes defining the corona.

“The corona has been observed with total solar eclipses for over a century, but never before had eclipse images been used to quantify its magnetic field structure,” Boe said in a release. “I knew it would be possible to extract a lot more information by applying modern image processing techniques to solar eclipse data.”

Boe traced the pattern of the distribution of magnetic field lines in the corona, using an automatic tracing method applied to images of the corona taken during 14 eclipses during the past two decades. This data provided the chance to study changes over two 11-year magnetic cycles of the sun.

Boe found that there were very fine-scale structures throughout the corona. Higher-resolution images showed smaller-scale structures, implying that the corona is even more structured than previously reported. To quantify these changes, Boe measured the magnetic field angle relative to the sun’s surface.

During periods of minimum solar activity, the corona’s field emanated almost straight out of the sun near the equator and poles, while it came out at a variety of angles at midlatitudes. During periods of maximum solar activity, the coronal magnetic field was far less organized and more radial.

“These results … indicate that the leading ideas for how to model the formation of the solar wind are not complete, and so our ability to predict and defend against space weather can be improved,” Boe said.

When the solar wind hits Earth, Earth’s magnetic field deflects the energy to the poles, creating the aurora borealis — the northern lights — and the equivalent in the south, the aurora australis.

Solar research is vital to any future settlement on the moon, which has no strong magnetic field. During a solar storm or flare, settlers would have to be indoors or would experience radiation sickness.

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