A total solar eclipse offers rare minutes when the Moon blocks the Sun's bright disk, revealing its outer atmosphere — the corona. In white light, the corona extends tens of solar radii, and images show fine structures: vortex rings, waves like ripples on water, and huge plasma ejections. Previously, astronomers only saw them close to the Sun because eclipse images are limited by the camera's field of view.
Now researchers have combined seven eclipse images with photographs taken by the Parker Solar Probe spacecraft. Its WISPR camera views the corona from close range and can track the motion of structures for weeks. It turns out the vortex rings don't disappear beyond the eclipse frame. They continue to travel away from the Sun, gradually accelerating. At a distance of three solar radii, their speed reaches about 249 kilometers per second. Closer to the surface, within one radius, the speed is lower — about 19 kilometers per second.
This means the vortex rings, born in complex magnetic fields near the Sun's surface, don't break apart but become embedded in the solar wind and are carried into interplanetary space. They are not a local phenomenon at the Sun's edge but part of a vast flow that bathes the entire solar system.
Eclipse observations provide a snapshot of the corona, while the probe's camera offers a movie. By combining them, astronomers have for the first time traced the fate of vortices over a vast distance. And it turns out these structures are long-lived. They travel from the Sun like leaves caught in the wind, retaining their shape along the way.
The speed of vortex rings at a distance of three solar radii is about 249 kilometers per second — faster than a rifle bullet.
In Arthur C. Clarke's novel "Solar Wind," characters race solar sails, riding the very streams of particles from the Sun in which vortex rings have now been found.