The aurora borealis is one of nature’s greatest wonders. As ethereal as it seems, this magical sight is the result of physics, and it begins with solar activity.
Every so often, the Sun burps out solar flares, which in turn cause violent geomagnetic storms.
NASA Goddard Space Flight Center
These storms ripple out and can hit the Earth’s magnetic field — these ripples are known as Alfven waves.
As the storms hit our magnetic field, they bring streams of electrons along for the ride. The charged particles collide with atoms and molecules in our atmosphere, exciting them in turn.
Basic Plasma Science Facility, University of California, Los Angeles
To come to their conclusions, the physicists put to the test a 40-year-old hypothesis that electrons surf Alfven waves. They did this by creating a simulation in UCLA’s Large Plasma Device, which is essentially 20 meter-long tunnel full of sensors.
Austin Montelius, College of Liberal Arts and Sciences, University of Iowa
The physicists found that streams of charged particles hitch a ride on Alfven waves, illustrated here by the yellow dots. The waves then travel along the magnetic fields in Earth’s atmosphere.
Electrons (yellow balls) accelerate toward the Earth along the magnetic field lines. Alfven waves follow (blue lines) and collide with errant atoms and molecules in the atmosphere (white balls).
Austin Montelius, College of Liberal Arts and Sciences, University of Iowa
They found that electron speeds increase with Alfven waves in a process called electron acceleration. The electrons sped up as the waves undulated, akin to how surfers gain speed as they ride a wave’s underside.
This research will help us better understand and predict space weather, says Howes. That includes its impact on our outer-space technology, like satellites and GPS.
Read more physics stories here.