"Our paper shows that the waves, which are created by what's known as the Kelvin-Helmholtz instability, happens much more frequently than previously thought," co-author Joachim Raeder of the University of New Hampshire (UNH) Space Science Center within the Institute for the Study of Earth, Oceans, and Space, said in a statement. "And this is significant because whenever the edge of Earth's magnetosphere, the magnetopause, gets rattled it will create waves that propagate everywhere in the magnetosphere, which in turn can energize or de-energize the particles in the radiation belts." In fact, data shows that Kelvin-Helmholtz waves actually occur 20 percent of the time at the magnetopause and can change the energy levels of our planet's radiation belts.
So why is this important? Well, first of all, Earth's magnetic field protects us from cosmic radiation. Not to mention these changing energy levels can potentially impact how the radiation belts either protect or threaten spacecraft and Earth-based technologies. But the UNH team presses that their discovery is less about the effects of so-called "space weather" and more about a better understanding of the basic physics of how the magnetosphere works. "It's another piece of the puzzle," Raeder said. "Previously, people thought Kelvin-Helmholtz waves at the magnetopause would be rare, but we found it happens all the time."
Kelvin-Helmholtz instability waves - named for 19th century scientists Lord William Thomson Kelvin and Hermann von Helmholtz - can be seen in everyday life, such as in cloud patterns, on the surface of oceans or lakes, or even in a backyard pool. The distinctive waves with capped tops and cloudless troughs are created by what's known as velocity shear, which occurs when a fluid or two different fluids - wind and water, for example - interact at different speeds to create differing pressures at the back and front ends of the wave.
Though these waves are ubiquitous in the Universe, their abundance was not known until scientists used data from NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, which launched in 2007 and provides unique, long-term observations. The results are described further in the journal Nature Communications.