It is widely thought that auroras require sunspots. Explosions in the magnetic canopies of sunspots can trigger geomagnetic storms and beautiful Arctic Lights. In fact, sunspots are not required. Behold this display, which appeared over Lohtaja, Finland, on Oct. 2nd when the sunspot number was near zero. "Bright auroras appeared around 11pm local time," says photographer Aku Kankaanpää. "The lights didn't last very long, but they lit up the stormy sea and seashore stones."
The cause of the display was a stream of solar wind, which has been pressing against Earth's magnetic field for days. The pressure is igniting intermittent geomagnetic storms and auroras around the Arctic Circle. The sunspot number is still low on Oct 3rd. Nevertheless, more auroras are possible tonight as the solar wind continues to blow.