Right before auroras dance in the sky, there’s often an appearance of a mysterious shape.
It drapes across the sky like a glowing pearl necklace.
Scientists call them auroral beads.
Structures like these can reveal how Earth’s magnetic field
interacts with solar material gushing through space.
Understanding these interactions better could help scientists protect
low-Earth orbiting satellites from extreme solar events.
But, until now, how the beads form has been a mystery.
With the help of NASA satellites and computer models,
scientists have the first evidence of how auroral beads form.
All auroras are created when charged particles from the Sun
are first trapped in Earth’s magnetic environment
and are then funneled into the atmosphere.
But scientists are now realizing that small changes in the magnetic environment
can cause big differences in how the aurora can look.
To analyze the auroral beads in more detail,
scientists took observations from NASA’s THEMIS mission.
Three of the THEMIS spacecraft study near-Earth phenomena that triggers auroras.
Scientists then combined THEMIS observations with ground measurements
and powerful computer models.
This is the result.
It’s a simulation of the near-Earth environment
that scientists can analyze on scales from tens of miles to 1.2 million miles.
They found that when particularly large streaming clouds of plasma from the Sun
reached Earth’s magnetic field,
they created buoyant bubbles of plasma behind the planet.
Just like a lava lamp, the buoyancy between the bubbles
and heavier plasma creates fingers of plasma about 2,500 miles wide
that stretch down towards Earth
creating the distinct pearl necklace structure in auroral beads.
From the ground the beads average about 30 miles wide.
Scientists hope these models will also be able to explain
other small-scale structures seen in the auroras.
The new results show us that even small, short-lived events within auroras
can be linked to big, global phenomena in our near-Earth environment.