* The Solar Enigma: Unraveling How Sunspot Umbra, the Sun’s Coldest Point, Fuels Its Multi-Million-Degree Corona

by François Dupont
Solar Orbiter Camera Modification

Pioneering research utilizing the Goode Solar Telescope at Big Bear Solar Observatory has unearthed potent wave energy from the sunspot umbra, potentially maintaining the Sun’s corona at temperatures of a million degrees. Although the discovery sheds new light on the Sun’s coronal heating dilemma, the enigma remains partially unresolved.

Researchers, using data from Big Bear Solar Observatory’s Goode Solar Telescope, have unveiled an intense wave energy presence in the Sun’s chilliest area, the sunspot umbra. This energy could be fueling the bafflingly high temperatures found in the star’s corona.

A perplexing question that has confounded solar physicists for a century lies about five thousand kilometers above the Sun’s surface: how can the Sun’s corona, its outer atmosphere, be hundreds of times hotter than its visible surface?

An international team of scientists offers a new perspective on this issue, often termed the Sun’s coronal heating problem, using novel observational data acquired with the 1.6-meter Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO), managed by NJIT’s Center for Solar Terrestrial Research (CSTR).

Published recently in Nature Astronomy, the study announces the discovery of intense wave energy emerging from a cool, dark, and highly magnetized plasma region on the Sun, capable of navigating the solar atmosphere and maintaining a million-degree Kelvin temperature within the corona.

Researchers state this discovery is a significant milestone in decoding a multitude of enigmas surrounding our closest star.

“Solving the coronal heating problem, one of the most persistent puzzles in solar physics research, has been our objective for nearly a century,” said Wenda Cao, BBSO director and NJIT physics professor, also a co-author of the study. “This research offers fresh insights, potentially helping us untangle various conundrums in energy transportation and dissipation in the solar atmosphere, as well as the nature of space weather.”

The team, led by Yuan Ding, used the unique imaging capabilities of the GST to observe transverse oscillations in the sunspot umbra, the darkest and coldest region on the Sun.

Strong magnetic fields create such dark sunspot regions, suppressing thermal conduction and blocking the energy flow from the hotter interior to the visible surface (or photosphere), where temperatures reach about 5,000 degrees Celsius.

The team investigated this by measuring the activity associated with many dark features spotted in an active sunspot recorded on July 14, 2015, by BBSO’s GST, including oscillatory transverse motions of plasma fibrils within the sunspot umbra, where the magnetic field is over 6,000 times stronger than Earth’s.

Vasyl Yurchyshyn, NJIT-CSTR research professor of heliophysics and BBSO senior scientist, explains that “Fibrils are cone-shaped structures with typical heights of 500-1,000 km and a width of approximately 100 km. Their lifespan is about two to three minutes, and they tend to reemerge at the same location within the darkest umbra areas, where the magnetic fields are most potent.”

“Our team has, for the first time, detected lateral oscillations of these dark dynamic fibrils in the sunspot umbra, manifestations of fast waves,” said Cao. “These persistent and pervasive transverse waves in highly magnetized fibrils channel energy upwards via vertically elongated magnetic conduits, contributing to the Sun’s upper atmosphere heating.”

Through simulating these waves numerically, the team estimates the energy transmitted could be thousands of times stronger than energy losses in active region plasma of

Frequently Asked Questions (FAQs) about Sun’s coronal heating problem

What is the primary discovery made by the research team?

The research team, utilizing the Goode Solar Telescope at Big Bear Solar Observatory, discovered intense wave energy in the sunspot umbra, the Sun’s coldest region. This energy may maintain the Sun’s corona at temperatures of a million degrees.

What is the Sun’s coronal heating problem?

The Sun’s coronal heating problem refers to the question that has baffled solar physicists for a century: why is the Sun’s upper atmosphere, or corona, hundreds of times hotter than its visible surface?

How does the sunspot umbra contribute to the heating of the Sun’s corona?

The research team found that the sunspot umbra, the Sun’s darkest and coldest region, experiences transverse oscillations or fast waves. These persistent waves in highly magnetized fibrils channel energy upwards through vertically elongated magnetic conduits, potentially contributing to the heating of the Sun’s upper atmosphere.

What are the implications of this research?

This research offers fresh insights into the Sun’s coronal heating problem and might help unravel various enigmas about energy transportation and dissipation in the solar atmosphere, as well as the nature of space weather.

Is the Sun’s coronal heating problem fully solved now?

No, the problem is not completely solved yet. While the new findings advance our understanding of the energy transport processes and heating of the solar corona, there remain sunspot-free regions associated with hot coronal loops that still need to be explained.

More about Sun’s coronal heating problem

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HelioFan June 21, 2023 - 7:16 am

I wonder how this discovery is gonna impact our understanding of space weather… seems like a big deal!

CosmicRay June 21, 2023 - 1:21 pm

Science never ceases to amaze! This research is gonna change our understanding of the sun. cant wait to see what’s next…

Heatwave21 June 21, 2023 - 3:05 pm

It’s interesting how somthing so cold can power something so hot. Guess we have a lot more to learn bout the sun.

StarryEyed June 21, 2023 - 5:43 pm

Just read the article, mind-blown… didn’t realize the coldest part of the sun could heat up the hottest! Science is amazing…

SolarJunkie99 June 21, 2023 - 8:07 pm

Wow!! I can’t believe they’re finally making progress on the coronal heating problem. this is like massive news for solar physics…Keep it up guys!


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