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First experimental proof of multiscale coupling in plasma has implications for fusion energy

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First experimental proof of multiscale coupling in plasma has implications for fusion energy


Prior to the equilibrium change, intense microscale magnetic turbulence is generated by electron beams injected into the two flux ropes. This turbulence induces three-dimensional magnetic reconnection. After the equilibrium change, the VEST device shows newly formed plasma (magenta) resulting from the reconnection of the two flux ropes, while the original flux ropes remain. In the simulation, the two flux ropes are observed to have merged into a single structure. Credit: Nature

Microscopic turbulence in plasma can trigger macroscopic structural changes. In complex physical systems, such cross-scale interactions—between different spatial and temporal scales—are known as multiscale coupling. To the best of their knowledge, Prof. Yong-Seok Hwang’s team, together with the Asia Pacific Center for Theoretical Physics, has now experimentally proven this phenomenon for the first time.

The work is published in the journal Nature.

The breakthrough resolves a long-standing puzzle in plasma physics, with implications for both fusion energy development and the study of astrophysical plasmas.

Seoul National University College of Engineering announced that a joint research team led by Prof. Yong-Seok Hwang from the Department of Nuclear Engineering, in collaboration with the Asia Pacific Center for Theoretical Physics (APCTP), has experimentally demonstrated the phenomenon of multiscale coupling in plasma—a long-standing puzzle in plasma physics—through the integration of fusion experiments and astrophysical plasma theory.

Initiated under the proposal of Prof. Hwang, who holds appointments in the Department of Nuclear Engineering and the Department of Energy Systems Engineering, the study was conducted solely by three Korean researchers.

The team included Dr. Jong Yoon Park, BK Assistant Professor at SNU and first author of the paper, and Dr. Young Dae Yoon, theoretical physicist at APCTP and corresponding author. This achievement, accomplished entirely by domestic researchers, is recognized as a milestone that significantly elevates Korea’s standing in global plasma science and technology research.

For plasma physicists, plasma—often called the “fourth state of matter,” distinct from solids, liquids, and gases—presents the formidable challenge of explaining how microscopic instabilities can drive macroscopic structural changes. The problem of multiscale coupling has therefore remained one of the most fundamental and long-standing issues in the field.

Plasma, however, is not only the essential medium for nuclear fusion reactions but also the predominant state of matter in the universe. Accordingly, understanding multiscale coupling in plasma has long been considered critical for both advancing fusion energy technology and unraveling the origins of the universe.

The team of Dr. Park and Dr. Yoon analyzed experimental data obtained from SNU’s fusion device and verified their findings through particle simulations using the KAIROS supercomputer at the Korea Institute of Fusion Energy. Their results proved that when microscopic magnetic turbulence is triggered, occurs effectively, inducing macroscopic structural changes within plasma.

The joint research team demonstrated for the first time that microscopic magnetic turbulence, deliberately induced by a strong electron beam, can increase plasma resistivity, thereby driving magnetic reconnection and ultimately producing large-scale structural changes—a direct experimental realization and proof of multiscale dynamics in plasma.

The study is particularly significant as an interdisciplinary achievement, combining experimental operations of Seoul National University’s fusion device with theoretical simulations conducted at APCTP.

This achievement also reflects the sustained efforts of Seoul National University and APCTP to provide early-career researchers with opportunities at an international level and to foster interdisciplinary collaboration. It stands as a representative case of advancing the global competitiveness of domestic researchers and nurturing future leaders in science and technology.

Dr. Jong Yoon Park, BK Assistant Professor at SNU, noted, “This outcome was only possible through countless discussions and debates between experts in fusion and theoretical physics, who started from different interests but ultimately arrived at common ground.

It is particularly meaningful in that it offers new clues to understanding the onset of magnetic reconnection, a process that plays a key role in cosmic phenomena such as solar flares and geomagnetic storms.”

Dr. Young Dae Yoon of APCTP added, “We hope this research will not only expand the framework of interpretation in but also serve as a foundation for the development of new technologies.”

More information:
Jong Yoon Park et al, Kinetic turbulence drives MHD equilibrium change via 3D reconnection, Nature (2025). DOI: 10.1038/s41586-025-09345-9

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The Best Presidents’ Day Deals on Gear We’ve Actually Tested

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The Best Presidents’ Day Deals on Gear We’ve Actually Tested


Presidents’ Day Deals have officially landed, and there’s a lot of stuff to sift through. We cross-referenced our myriad buying guides and reviews to find the products we’d recommend that are actually on sale for a truly good price. We know because we checked! Find highlights below, and keep in mind that most of these deals end on February 17.

Be sure to check out our roundup of the Best Presidents’ Day Mattress Sales for discounts on beds, bedding, bed frames, and other sleep accessories. We have even more deals here for your browsing pleasure.

WIRED Featured Deals

Branch Ergonomic Chair Pro for $449 ($50 off)

  • Photograph: Julian Chokkattu

  • Photograph: Julian Chokkattu

  • Photograph: Julian Chokkattu

Branch

Ergonomic Chair Pro

The Branch Ergonomic Chair Pro is our very favorite office chair, and this price matches the lowest we tend to see outside of major shopping events like Black Friday and Cyber Monday. It’s accessibly priced compared to other chairs, and it checks all the boxes for quality, comfort, and ergonomics. Nearly every element is adjustable, so you can dial in the perfect fit, and the seven-year warranty is solid. There are 14 finishes to choose from.



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Zillow Has Gone Wild—for AI

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Zillow Has Gone Wild—for AI


This will not be a banner year for the real estate app Zillow. “We describe the home market as bouncing along the bottom,” CEO Jeremy Wacksman said in our conversation this week. Last year was dismal for the real estate market, and he expects things to improve only marginally in 2026. (If January’s historic drop in home sales is indicative, that even is overoptimistic.) “The way to think about it is that there were 4.1 million existing homes sold last year—a normal market is 5.5 to 6 million,” Wacksman says. He hastens to add that Zillow itself is doing better than the real estate industry overall. Still, its valuation is a quarter of its high-water mark in 2021. A few hours after we spoke, Wacksman announced that Zillow’s earnings had increased last quarter. Nonetheless, Zillow’s stock price fell nearly 5 percent the next day.

Wacksman does see a bright spot—AI. Like every other company in the world, generative AI presents both an opportunity and a risk to Zillow’s business. Wacksman much prefers to dwell on the upside. “We think AI is actually an ingredient rather than a threat,” he said on the earnings call. “In the last couple years, the LLM revolution has really opened all of our eyes to what’s possible,” he tells me. Zillow is integrating AI into every aspect of its business, from the way it showcases houses to having agents automate its workflow. Wacksman marvels that with Gen AI, you can search for “homes near my kid’s new school, with a fenced-in yard, under $3,000 a month.” On the other hand, his customers might wind up making those same queries on chatbots operated by OpenAI and Google, and Wacksman must figure out how to make their next step a jump to Zillow.

In its 20-year history—Zillow celebrated the anniversary this week—the company has always used AI. Wacksman, who joined in 2009 and became CEO in 2024, notes that machine learning is the engine behind those “Zestimates” that gauge a home’s worth at any given moment. Zestimates became a viral sensation that helped make the app irresistible, and sites like Zillow Gone Wild—which is also a TV show on the HGTV network—have built a business around highlighting the most intriguing or bizarre listings.

More recently, Zillow has spent billions aggressively pursuing new technology. One ongoing effort is upleveling the presentation of homes for sale. A feature called SkyTour uses an AI technology called Gaussian Splatting to turn drone footage into a 3D rendering of the property. (I love typing the words “Gassian Splatting” and can’t believe an indie band hasn’t adopted it yet.) AI also powers a feature inside Zillow’s Showcase component called Virtual Staging, which supplies homes with furniture that doesn’t really exist. There is risky ground here: Once you abandon the authenticity of an actual photo, the question arises whether you’re actually seeing a trustworthy representation of the property. “It’s important that both buyer and seller understand the line between Virtual Staging and the reality of a photo,” says Wacksman. “A virtually staged image has to be clearly watermarked and disclosed.” He says he’s confident that licensed professionals will abide by rules, but as AI becomes dominant, “we have to evolve those rules,” he says.

Right now, Zillow estimates that only a single-digit percentage of its users take advantage of these exotic display features. Particularly disappointing is a foray called Zillow Immerse, which runs on the Apple Vision Pro. Upon rollout in February 2024, Zillow called it “the future of home tours.” Note that it doesn’t claim to be the near-future. “That platform hasn’t yet come to broad consumer prominence,” says Wacksman of Apple’s underperforming innovation. “I do think that VR and AR are going to come.”

Zillow is on more solid ground using AI to make its own workforce more productive. “It’s helping us do our job better,” says Wacksman, who adds that programmers are churning out more code, customer support tasks have been automated, and design teams have shortened timelines for implementing new products. As a result, he says, Zillow has been able to keep its headcount “relatively flat.” (Zillow did cut some jobs recently, but Wacksman says that involved “a handful of folks that were not meeting a performance bar.”)



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Do Waterproof Sneakers Keep the Slosh In or Out? Let WIRED Explain

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Do Waterproof Sneakers Keep the Slosh In or Out? Let WIRED Explain


Running with wet feet, in wet socks, in wet shoes is the perfect recipe for blisters. It’s also a fast track to low morale. Nothing dampens spirits quicker than soaked socks. On ultra runs, I always carry spares. And when faced with wet, or even snowy, mid-winter miles, the lure of weatherproof shoes is strong. Anything that can stem the soggy tide is worth a go, right?

This isn’t as simple an answer as it sounds. In the past, a lot of runners—that includes me—felt waterproof shoes came with too many trade-offs, like thicker, heavier uppers that change the feel of your shoes or a tendency to run hot and sweaty. In general, weatherproof shoes are less comfortable.

But waterproofing technology has evolved, and it might be time for a rethink. Winterized shoes can now be as light as the regular models, breathability is better, and the comfort levels have improved. Brands are also starting to add extra puddle protection to some of the most popular shoes. So it’s time to ask the questions again: Just how much difference does a bit of Gore-Tex really make? Are there still trade-offs for that extra protection? And is it really worth paying the premium?

I spoke to the waterproofing pros, an elite ultra runner who has braved brutal conditions, and some expert running shoe testers. Here’s everything you need to know about waterproof running shoes in 2026. Need more information? Check out our guide to the Best Running Shoes, our guide to weatherproof fabrics, and our guide to the Best Rain Jackets.

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How Do Waterproof Running Shoes Work?

On a basic level, waterproof shoes add extra barriers between your nice dry socks and the wet world outside. If you’re running through puddles deep enough to breach your heel collars, you’re still going to get wet feet. But waterproof shoes can protect against rain, wet grass, snow, and smaller puddles.

Gore-Tex is probably the most common waterproofing tech in footwear, but it’s not the only solution in town. Some brands have proprietary tech, or you might come across alternative systems like eVent and Sympatex. That GTX stamp is definitely the one you’re most likely to encounter, so here’s how GTX works.

The water resistance comes from a layered system that is composed of a durable water repellent (DWR) coating to the uppers with an internal membrane, along with other details like taped seams, more sealed uppers with tighter woven mesh, gusseted tongues, and higher, gaiter-style heel collars.



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