Our atmosphere isn’t the only place where turbulence is found: it happens out in space too. And now, for the first time, a team led by the University of Iowa has recreated and measured this phenomenon in the laboratory.
One source of these ‘space winds’ is the violent emission of charged particles from the sun, known as coronal mass ejections, or CMEs. Responsible for auroras, these can also adversely affect satellite communications, air travel and the electric power grid, making understanding them a priority.
“Turbulence is not restricted to environments here on Earth, but also arises pervasively throughout the solar system and beyond, driving chaotic motions in the ionized gas, or plasma, that fills the universe,” says Gregory Howes, assistant professor of physics and astronomy.
“It is thought to play a key role in heating the atmosphere of the sun, the solar corona, to temperatures of a million degrees Celsius, nearly a thousand times hotter than the surface of the sun.”
Turbulence also regulates the formation of the stars throughout the galaxy, he says, determines the radiation emitted from the supermassive black hole at the center of our galaxy and affects space weather here on Earth.
Unlike gusts of wind on the surface of Earth, turbulent motions in space and astrophysical systems are governed by Alfven waves, which are traveling disturbances of the plasma and magnetic field.
And the basis of plasma turbulence appears to be nonlinear interactions between Alfven waves traveling up and down the magnetic field, such as two magnetic waves colliding to create a third wave.
Howes’s work supports that idea, by actually measuring this interaction.
“We have presented the first experimental measurement in a laboratory plasma of the nonlinear interaction between counter-propagating Alfven waves, the fundamental building block of astrophysical turbulence,” says Howes.