Night sky ‘necklace of shining pearls’ mystery solved, NASA says

The next time you wait for the Northern Lights or the Northern Lights to arrive – maybe in Alaska, northern Canada, Iceland, northern Norway, Finland or Sweden – look for “auroral pearls.” Because something special is about to happen.

NASA’s THEMIS fleet of spacecraft has uncovered the truth about a very special type of aurora, also known as the “Northern Lights” in the Northern Hemisphere.

Described as “like a shining pearl necklace,” the phenomenon of “auroral pearls” can sometimes be seen just before major auroral displays, but so far scientists have been puzzled.

What are the aurora?

The Northern Lights are a natural phenomenon of the sky observed near the Arctic Circle (Aurora Borealis or Aurora Borealis) and the Antarctic Circle (Aurora Australis or Aurora Australis).

They are caused by charged particles from the Sun captured and accelerated by the Earth’s magnetosphere to interact with atoms in the upper atmosphere.

What are “auroral pearls”?

They are pearls that light up the sky like unique pearls in a shiny “auroral necklace”, scientists say.

Usually, they appear when the aurora begins to light up, so in addition to being a mystery in itself, it is believed that they could cause – or indicate the coming – impressive aurora displays.

What causes “auroral beads”?

They are caused by the turbulence of the plasma in the space surrounding the Earth, and not in the Earth’s upper atmosphere, as previously suspected.

“We now know for sure that the formation of these beads is part of a process that precedes the onset of a sub-storm in space,” said Vassilis Angelopoulos, THEMIS principal investigator at the University of California at Los Angeles. “It’s an important new piece of the puzzle.”

As the plasma ejected by the Sun interacts with the Earth’s magnetic field, it creates plasma bubbles floating behind the Earth, scientists say. Comparing it to a lava lamp, they explain that the imbalances in the buoyancy between the bubbles and the heavier plasma in the magnetosphere create 2,500-mile-wide plasma fingers that extend toward Earth.

This is what causes “auroral beads”. The results were published today in the Geophysical Research Letters and Journal of Geophysical Research: Space Physics.

What is NASA’s THEMIS mission?

It is a fleet of three spacecraft orbiting the Earth. Since its launch in 2007, THEMIS has been taking detailed measurements as it passes through the magnetosphere to help scientists understand the causes of sub-storms that lead to auroras.

By modeling the near-Earth environment at scales ranging from tens of miles to 1.2 million miles, THEMIS scientists were able to show the details of the formation of auroral beads.

“There are a lot of very dynamic, very small-scale structures that people see in the Northern Lights that are difficult to connect to the larger picture in space because they happen very quickly and on a very small scale.” said Kareem Sorathia, lead author of one of the new papers and scientist from NASA’s Center for Geospace Storms, headquartered at the Johns Hopkins Applied Physics Laboratory. “Now that we can use global models to characterize and study them, this opens up a lot of new doors.”

I wish you clear skies and wide eyes.