"Surfer" tube-shaped waves are created when a speedy fluid, like wind, moves over a sluggish one, like water. These so-called Kelvin-Helmholtz waves occur everywhere in the universe, as you can see in the image of Saturn's upper atmosphere, above. They also happen when solar winds strike the Earth's protective magnetosphere, and researchers now believe that they occur much more often there than we thought. Not only that, but they might cause the magnetosphere to be charged with plasma, affecting how it works to protect life on our planet from radiation.
The first team from the University of New Hampshire examined the Earth's magnetic field with NASA's THEMIS and Advanced Composition Explorer (ACE) craft. When solar winds blow past our magnetosphere, scientists thought they could only create surfer-type waves when the sun's magnetic field is aligned with Earth's. But using ACE, which is parked between the Earth and the sun, and THEMIS, which orbits near our magnetosphere, they found that wasn't necessarily the case. Instead, Kelvin-Helmholtz waves can occur practically any time, regardless of solar wind speeds and the direction of magnetic fields.
Another team from Boston University and Virginia Tech then figured out why such waves might occur so often. They found that just before Kelvin-Helmholtz waves start propagating at the magnetosphere's boundary, a thin plume of plasma shoots out, depositing extra atoms. The researchers think those plumes may actually trigger the waves, since it bumps up the density of the magnetosphere boundary compared to the solar winds blasting past it -- just like wind blowing over water.
Scientists aren't sure whether such waves can trigger space weather events near our home planet. Nevertheless, they now think that Kelvin-Helmholtz waves could cause solar plasma to get into the Earth's magnetosphere, affecting how it behaves. And since the magnetosphere is what protects all of us from getting cooked by radiation, that sounds like a good thing to know.