Torrents of charged particles continuously lift off the sun’s atmosphere and radiate outward at millions of kilometers per hour, yielding a solar wind so immense that its limit defines the outer edge of our solar system.

Despite the vast reach of this wind, its formation has long been a puzzle. Now a new analysis argues that the solar wind is powered by a collective set of intermittent, small-scale jetlike eruptions in the sun’s corona, or outer layer. “The idea is similar to how individual clapping sounds in an auditorium become a steady roar as an audience applauds,” said Craig DeForest, a solar physicist at the Southwest Research Institute in Boulder, Colorado, and a co-author of the study.

While scientists already knew that the corona was home to small jetlets that typically last for several minutes, they had previously discovered only a small number of them, mainly at the base of plumes emerging from cooler, less dense regions of the corona known as coronal holes.

The new study reveals that they’re ubiquitous. “Once you know how to find them, you see that they are everywhere in basically every structure in the corona all the time,” said co-author Dan Seaton, a solar physicist who is also at the Southwest Research Institute.

The team found that the jetlets, each between 1,000 and 3,000 kilometers wide, are present even during the solar minimum, the least active phase of the sun’s 11-year cycle — a result that’s consistent with the solar wind’s pervasive nature. “You can randomly pick any day and the jetlets are there, just like the solar wind,” said Nour Raouafi, a solar physicist at the Johns Hopkins University Applied Physics Laboratory and lead author of the study.

In the paper laying out the new findings, published last month in the Astrophysical Journal, the team provides evidence that the jetlets are sparked by a process called magnetic reconnection, which heats and accelerates a plasma of charged particles. The researchers suggest that the jetlets then produce waves that heat the corona and enable the plasma to escape the sun’s gravity and coalesce to form the solar wind.

“The numbers come out looking promising and show it is really quite possible that jetlets could supply the mass lost by the sun to the solar wind,” said Charles Kankelborg, a solar physicist at Montana State University who was not involved with the study.

The Engine

The idea that small-scale, intermittent events could collectively drive the solar wind stems from the work of Eugene Parker, a pioneering solar physicist who died last year. In 1988, he suggested that a “swarm of nanoflares” driven by tiny bursts of magnetic reconnection could heat the corona enough to power the wind.