The aurora borealis is one of the most stunning light shows on Earth, but normally, it’s a treat reserved for the hardy souls living at the coldest edges of the world. The last few nights, however, people across the Northern and Southern hemispheres have enjoyed dazzling, colorful skies, thanks to a geomagnetic storm that began early this week and may continue through tomorrow.
What causes auroras? It all starts when things get a little heated on the surface of the Sun. Heightened solar activity can produce flares—streams of high energy light waves and charged particles. In some instances, the Sun will belch a giant cloud of magnetized plasma off into space; a phenomena known as a coronal mass ejection. When solar material from these eruptions makes its way to Earth, it bumps into our planet’s magnetic field, triggering geomagnetic storms.
Bright shaded areas in the map above indicate regions likely to see auroras tonight as a result of this week’s solar activity. Image Credit: NOAA
The aurora occurs when a disturbance in the magnetic field sends charged particles falling toward the Earth, where they collide with molecules in the atmosphere, releasing light. Oxygen molecules emit yellowish-green light when they get charged up, while nitrogen produces brilliant blues and purplish-reds.
According to NASA, this week’s auroras—which have been visible as far south as Wisconsin and New York State—are the result of a high-speed solar wind stream, flowing out of a “coronal hole” on the surface of the Sun. Neat. Let’s see what that looks like to Earthlings across the world.
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Top image: Scott Pearson / Twitter