Kelvin-Helmholtz waves routinely perturb Earth's magnetic field

DURHAM, N.H., May 11 (UPI) -- Kelvin-Helmholtz waves are seemingly everywhere. But for some reason, scientists believed they were almost absent from Earth's magnetic field, or magnetosphere.

A new study finds that the opposite is true -- that the Earth's magnetic field is often perturbed by Kelvin-Helmholtz waves. Researchers at the University of New Hampshire say the waves are especially ubiquitous at the edge of field, a region known as the magnetopause.

Kelvin-Helmholtz waves are created by the instability born of velocity shear -- the interaction of two fluids, or two parts of single fluid, at varying speeds. These waves manifest themselves on the surface on a pond or backyard pool when the wind blows. They can be seen in form of clouds with capped tops and cloudless troughs. And they, apparently, can be found throughout the magnetopause.

The discovery was made by postdoctoral student Shiva Kavosi -- lead author of the new study -- and his mentor Joachim "Jimmy" Raeder, a researcher with New Hampshire's Institute for the Study of Earth, Oceans and Space. Their research was made possible my newly collected data from NASA's THEMIS mission, a five-satellite effort to study the magnetosphere.

"Previous missions were either too short or the observations didn't occur in the right place," Raeder explained in a press release. "THEMIS's elliptical orbits achieved over one thousand magnetopause crossings and provided unprecedented observations. We didn't have a database like this before and therefore couldn't do the analysis."

Their research suggests Kelvin-Helmholtz instability at the edge of the magnetosphere may open the door to electromagnetic plasma, allowing solar winds to penetrate the Earth's protective shield.

"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."

But more than illuminate the behavior of solar weather systems, the new research reveals the physics that govern the magnetosphere.

"It's another piece of the puzzle," Raeder says. "Previously, people thought Kelvin-Helmholtz waves at the magnetopause would be rare, but we found it happens all the time."

The research was recently published in the journal Nature Communications.