Laser-blasted plasma shows how instabilities could heat the sun's corona

October 26, 2026 report Laser-blasted plasma shows how instabilities could heat the sun's corona Sam Jarman Author Sadie Harley Scientific Editor Robert Egan Senior Editor From its visible surface, the sun radiates heat at a relatively cool temperature of 5,800 Kelvin. Yet within the thin outer layer of the sun's atmosphere known as the corona, electrons can reach temperatures of millions of degrees, for reasons astronomers have yet to fully explain. Through new research published in Physical Review Letters, a team led by Wei Sun at the China Institute of Atomic Energy has recreated corona-like conditions in the lab. Their experiment shows how this dramatic heating could be driven by instabilities in the corona's plasma, which trigger tiny bursts of energy called 'nanoflares.' Missing evidence The leading explanation for coronal heating begins at the sun's surface, where churning plasma slowly twists and stretches the magnetic fields reaching up into the corona, storing energy within them. Eventually, inside thin sheets of electrical current, magnetic field lines pointing in opposite directions can break and rejoin in a process called 'reconnection,' suddenly releasing this energy. Each nanoflare is small by solar standards, but could launch jets of plasma and briefly heat its surroundings to extreme temperatures. Separately, observations have revealed finger-like structures forming where dense drops of cooler plasma fall through the thinner plasma around them, in a process astronomers call 'coronal rain.' Much like a heavy liquid resting on top of a lighter one, this arrangement is unstable. Simulations have suggested that these fingers can squeeze magnetic fields together, triggering reconnection and small plasma jets. So far, however, no direct evidence has connected these effects to nanoflare heating. Solar corona in the lab To create their analog of the corona, Sun's team used China's Shenguang-II laser facility. They fired powerful laser beams at tiny plastic targets with wavy surfaces. This produced a plasma just millimeters across, with instabilities seeded in a precisely controlled way. Although far smaller than anything on the sun, the plasma was tuned to behave in a similar way to the plasma around coronal rain. The researchers then tracked the plasma's structure and magnetic fields using optical imaging, and estimated its electron temperatures by analyzing the X-rays it emitted. For comparison, they repeated the experiment using flat targets, where no instabilities could form. Triggering reconnection The result was the first-ever lab demonstration of nanoflare heating driven by plasma instabilities. With the wavy targets, the team reproduced the finger-like structures seen in the real corona, which pushed oppositely directed magnetic fields together and drove reconnection. This allowed electrons to reach around 820,000 K: about twice the maximum temperature produced by the flat targets. Accompanying computer simulations showed that electrical heating within the reconnecting current layers far outweighed heating through friction within the plasma. When the simulations suppressed the generation of magnetic fields, most of the extra heating vanished, strengthening the magnetic explanation. The result could fill an important gap in our understanding of how the corona is heated. Sun's team now hopes to build on their experiment with more 3D plasmas and more precise measurements. This in turn could help researchers answer remaining questions about how widely the mechanism operates, and whether nanoflares occur often enough to explain a large fraction of the corona's heat. Written for you by our author Sam Jarman, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you. Publication details Wei Sun et al., Laboratory Demonstration of Coronal Heating via Magnetic Reconnection during Nanoflares, Physical Review Letters (2026). DOI: 10.1103/tmll-l58c Journal information: Physical Review Letters © 2026 Science X Network