Earlier observations of the sun had already indicated that solar wind comes out of what are known as coronal holes, regions where the magnetic field continues far outward into space instead of wrapping around and coming back down at another point on the sun.

Imagine a simple bar magnet, which generates a magnetic field similar in shape to the one that surrounds Earth. At the poles, the magnetic fields go straight up and down; those are the coronal holes.

During the sun’s quiet periods — solar activity varies on an 11-year cycle, from comparatively calm to hyperactive — the sun’s magnetic field possesses this bar magnet configuration. When the Parker spacecraft launched, the sun was near its minimum.

But as the sun approaches the maximum of its cycle, when the magnetic field is in the throes of reversing direction, the structure of the field becomes more complex, and more coronal holes appear.

The Parker spacecraft’s instruments detected that the solar wind was not uniform over coronal holes. Instead, the particles emerged in “microstreams,” like jets from a shower head.

The space probe’s sensors “started seeing that the solar wind had a huge amount of structure,” said James Drake, a professor of physics at the University of Maryland and another author of the Nature paper.