during transient seizures, The sun sometimes throws a huge amount of energy into space. Called solar flares, these outbursts last only minutes, and can lead to catastrophic blackouts and spectacular aurorae on Earth. But our leading mathematical theories of how these flares work fail to predict the strength and speed of what we observe.
At the heart of these explosions is a mechanism that converts magnetic energy into powerful blasts of light and particles. This shift is catalyzed by a process called magnetic reconnection, in which colliding magnetic fields break and instantly realign, flinging matter out into the universe. In addition to powering solar flares, reconnection may power fast, high-energy particles ejected by exploding stars, jet flares from molten black holes, and constant winds blown by the sun.
Despite its ubiquity, scientists have struggled to understand how it works efficiently. A recent theory suggests that when it comes to solving the mysteries of magnetic reconnection, little physics plays a big role. In particular, it explains why some reconnection events are startlingly fast — and why the strongest seem to happen with characteristic speed. Understanding the subtle physics of reconnection can help researchers build better models of these energetic outbursts and make sense of cosmic outbursts.
“So far, this is the best theory I can see,” said Hantao Ji, a plasma physicist at Princeton University who was not involved in the study. “It’s quite an achievement.”
Almost all known matter in the universe exists in the form of plasma, a fiery soup of gas where hellish temperatures have stripped atoms and turned them into charged particles. As they move, these particles generate magnetic fields, which in turn direct the particles’ motions. This chaotic interaction creates a jumbled mess of magnetic field lines that, like rubber bands, store more and more energy as they are stretched and twisted.
In the 1950s, scientists proposed an explanation for how plasma releases its pent-up energy, a process that has been called magnetic reconnection. When magnetic field lines pointing in opposite directions collide, they can catch and intersect, launching particles like a double-sided slingshot.
But this idea was more of an abstract painting than a complete mathematical model. The scientists wanted to understand the details of how the process works — the events that affect the attraction, and why so much energy is released. But the chaotic interaction of hot gas, charged particles, and magnetic fields is difficult to tame mathematically.
The first quantum theory, described by astrophysicists Peter Sweet and Eugene Parker in 1957, treats plasmas as magnetized fluids. He proposes that collisions of oppositely charged particles attract magnetic field lines and set off a wild chain of reconnection events. Their theory also predicts that this process occurs at a certain rate. Reconnection rates observed in the relatively weak laboratory pseudo-plasma match their predictions, as do the rates of smaller jets in the lower layers of the heliosphere.
But solar flares release energy much faster than Sweet and Parker’s theory can explain. By their calculations, those flares should last over months, rather than minutes.
Recently, observations from NASA’s magnetosphere satellites determined that this faster reconnection occurs closer to home, in Earth’s magnetic field. These observations, along with evidence from decades of computer simulations, confirm this “rapid” reconnection rate: in the most energetic plasma, reconnection occurs at about 10 percent of the speed at which magnetic fields propagate — orders of magnitude Faster than Sweet and Parker’s theory predicts. .