19 September 2017

Giant ‘space hurricanes’ propelled by solar wind may impact satellite safety, study finds

Posted by Lauren Lipuma

Kelvin Helmholtz instability clouds in San Francisco. These clouds, sometimes called “billow clouds,” are produced by atmospheric instability, when horizontal layers of air brush by one another at different velocities. A new study finds that Kelvin Helmholtz instabilities in Earth’s magnetosphere, called space hurricanes, can impact satellite safety by altering space weather near Earth.
Credit: Brocken Inaglory, own work, public domain.

By Ginger Pinholster

Could the flapping of a butterfly’s wings in Costa Rica set off a hurricane in California? The question has been scrutinized by chaos theorists, stock-market analysts and weather forecasters for decades. For most people, this hypothetical scenario may be difficult to imagine on Earth – particularly when a real disaster strikes.

Yet, in space, similarly small fluctuations in the solar wind as it streams toward the Earth’s magnetic shield can affect the speed and strength of “space hurricanes,” researchers report in a new study in the Journal of Geophysical Research: Space Physics, a journal of the American Geophysical Union.

The new study offers the first detailed description of the mechanism by which solar wind fluctuations can change the properties of so-called space hurricanes. Those “hurricanes” are formed by a phenomenon known as Kelvin-Helmholtz (KH) instability. As plasma from the sun (solar wind) sweeps across Earth’s magnetic boundary, it can produce large vortices about 10,000 to 40,000 kilometers (6,000 to 25,000 miles) in size along the boundary layer, said Katariina Nykyri, a space physicist at Embry-Riddle Aeronautical University in Daytona Beach, Florida and lead author of the new study.

“The KH wave, or space hurricane, is one of the major ways that solar wind transports energy, mass and momentum into the magnetosphere,” Nykyri said. “Fluctuations in solar wind affect how quickly the KH waves grow and how large they become.”

When solar wind speeds are faster, the fluctuations are more powerful and seed larger space hurricanes that can transport more plasma, Nykyri said.

A Kelvin-Helmholtz instability on Saturn, caused by the interaction between two bands of the planet’s atmosphere. Image from the Cassini probe.
Credit: NASA.

Gaining deeper insights into how solar wind conditions affect space hurricanes may someday provide better space-weather prediction and set the stage for safer satellite navigation through radiation belts, Nykyri said. This is because solar wind can excite ultra-low frequency (ULF) waves by triggering KH instability, which can energize radiation belt particles.

Space hurricanes are universal phenomena, occurring at the boundary layers of coronal mass ejections – giant balls of plasma erupting from the Sun’s hot atmosphere – in the magnetospheres of Jupiter, Saturn and other planets, Nykyri noted.

“KH waves can alter the direction and properties of Coronal Mass Ejections, which eventually affect near-Earth space weather,” Nykyri explained. “For accurate space weather prediction, it is crucial to understand the detailed mechanisms that affect the growth and properties of space hurricanes.”

In addition to playing a role in transporting energy and mass, KH waves also provide an important way of heating plasma by millions of degrees Fahrenheit and may be important for solar coronal heating. They might also be used for transport barrier generation in fusion plasmas.

For the current research, simulations were based on seven years’ worth of measurements of the amplitude and velocity of solar wind fluctuations at the edge of the magnetosphere, as captured by NASA’s THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft.  

Ginger Pinholster is the Interim Vice President of Marketing and Communications at Embry-Riddle Aeronautical University. This post originally appeared as a press release on the Embry-Riddle website.