You probably best recognize it as the shape of a surf wave, but that’s only the beginning. They’re called Kelvin-Helmholtz waves—and from our own oceans to the outer reaches of space, they’ve been showing up everywhere.
Scientists actually first started identifying the pattern as Kelvin-Helmholtz waves in the 1800s, but people have been noticing them out in nature even before that. It’s no surprise—their shape is distinctive, a line of parallel peaks that resolve themselves into a series of hooks—and is not only often spotted in the ocean, but also in the clouds above.
A pair of new NASA studies, though, have found that Kelvin-Helmholtz waves are much more common outside the bounds of Earth than we originally thought, especially in the space right around us. Researchers knew the waves sometimes showed up and had even spotted them in the atmospheres around other planets. But, with better instruments, we’re now able to better see what’s going in our magnetosphere and plasmasphere, and Kelvin-Helmholtz waves have been popping up all over both.
So what do these Kelvin-Helmholtz waves look like when they’re not being made by clouds or water? Still pretty much like surf waves, only with a little more drama, like in this simulation of Earth’s magnetosphere as a strong solar wind sails by it:
But what causes Kelvin-Helmholtz waves and why are they are turning out to be so common not just in our own world, but beyond?
Essentially, they show up when two fluids move past each other in a way that makes that boundary suddenly unstable. Here’s a demonstration from the University of Cambridge that shows exactly how the process unfolds:
Once you’ve seen how they’re created, it’s not quite as surprising that we’re seeing more of them in space. They can be generated by the meetings of anything from wind to plasma to water to a planet’s atmosphere—all things that space is full of. In fact, the more we see of space, the more likely we are to see more of these surf waves.
Top image: Clouds in Denmark Henrik Bondo via USRA; Middle Image: S. Kavosi/J. Raeder/UNH via NASA.