The auroral light shows that appear in the sky near Earth’s poles — aurora borealis in the North, aurora australis in the South — have captivated humans for centuries and contributed to mythology around the world.
We now know that auroras are caused by electrons and other charged particles from the sun being funneled by Earth’s magnetic field towards the poles, where they hit air molecules in Earth’s upper atmosphere at 45 million miles per hour. The energy from the collision causes the molecules to give off bursts of light. Put together the tiny bursts of light from a bunch of molecules — green and red from oxygen, blue and purple from nitrogen — and you get the shimmering colors of an aurora.
But researchers weren’t sure exactly how auroral electrons could be accelerated to the energy they were observed hitting the atmosphere with. Now, a group of physicists have answered that question with an experiment showing that aurora-causing electrons can accelerate towards Earth by “surfing” on plasma waves created by solar weather disturbing Earth’s magnetic field.
