Fastest-moving solar storm in years triggered beautiful green and purple aurora

In Finland, the “aurora did one amazing dance just after the fall of darkness,” Alexander Kuznetsov, a self-described “aurora hunter,” wrote on SpaceWeather.com. “It started as a sharp dancing arc in the Southern horizon, and it quickly went overhead, producing some of the most vibrant red & purple auroras that I’ve seen in my entire aurora hunting career!”

Matti Helin, another aurora watcher in southwest Finland, said a “nice display” lasted just 20 minutes.

The strong solar storm and brilliant light displays come as the sun ramps up to its most active in two decades. Scientists expect more to auroral activity in the following years, including in upcoming months.

Intense eruptions on the sun

Auroras are initiated when the sun sends a surge of solar particles toward Earth and disturbs our magnetic field — creating a geomagnetic storm. The solar particles excite oxygen and nitrogen molecules in our upper atmosphere and release photons of light, which we see as the aurora.

Geomagnetic storms are rated on a scale of 1 (minor) to 5 (extreme) by NOAA’s Space Weather Prediction Center. Sunday’s geomagnetic storm reached up to G4 but weakened to G2 and G1 levels just a few hours later.

The fast stream of solar particles continued to buffet Earth’s magnetic field on Monday morning, still moving at twice its normal speed. But the chance for strong aurora activity has subsided because geomagnetic activity has weakened, said Bill Murtagh, program coordinator for NOAA’s Space Weather Prediction Center.

The best auroral displays occurred in parts of Europe and the southern hemisphere, when the G4 activity coincided with evening or nighttime. Unfortunately, the G4 conditions occurred during the daytime for the United States, when our sun masked the light display, but northern parts of the country still saw some dancing lights during the weaker geomagnetic storming at night.

New Zealand, where it was pre-dawn when the solar storm hit, was well-positioned for an aurora display.

“While clouds interfered with the view, the aurora was strong despite the full moon,” Ian Griffin, a photographer on New Zealands Otago Peninsula, wrote on SpaceWeather.com.

Scientists traced the geomagnetic activity to a group of sunspots, or dark, cooler regions on the sun, last week. Sunspots are areas where the sun’s magnetic field is very strong. Magnetic field lines near the sunspots often tangle, cross and reorganize until pressure builds and causes a big release of energy, Murtagh said.

Activity around the sunspots erupted Friday evening. One event was an impressive solar flare, which sent an intensive wave of electromagnetic radiation to the Earth. The solar flare event lasted several hours and hammered radio communication, according to space weather scientist Tamitha Skov.