Satellite Image Maps Extreme Solar Storm’s Stunning Aurora Over US

Images taken from space have revealed the spectacular extent of the far-reaching northern lights this weekend.

These gorgeous aurorae were visible from all 50 U.S. states on the night of May 10 and were triggered by a powerful G5 geomagnetic storm.

This geomagnetic storm—caused by a train of coronal mass ejections (CMEs) fired toward us from the sun—was the most powerful that we have seen since 2003.

Images taken from the NOAA-20, NOAA-21, and S-NPP satellites have revealed what this cosmic phenomenon looked like from Earth’s orbit, albeit in black and white rather than in the aurora’s natural green and purple.

In the pictures, the aurora can be seen stretching across the U.S. While it appears to only reach as far south as Ohio, Pennsylvania and the Dakotas, the lights were spotted by locals as far south as Florida and Mexico.

The northern and southern lights can be triggered by geomagnetic storms, which are disruptions to the Earth’s magnetic field caused by coronal mass ejections of solar plasma from the sun. These CMEs interact with the Earth’s magnetosphere, a protective magnetic field that surrounds our planet, sparking a geomagnetic storm.

Geomagnetic storms vary in strength depending on the CME’s speed and magnetic field, and are classed on a scale of G1 (minor) to G5 (extreme). This weekend’s storm was the first G5 storm seen since 2003.

“G5 or a severe geomagnetic storm is not very common at all. On average we might encounter these conditions over four days during an entire solar activity cycle. That would be over 11 years. Such conditions are rare as they require a substantial activity to be present on the sun’s surface for starters,” Daniel Brown, an associate professor in astronomy and science communication at Nottingham Trent University, in the United Kingdom, told Newsweek.

“So there needs to be a large strong and complex sunspot there with substantial potential for flares, i.e. releasing massive energies built up through tension in the ever-twisting magnetic field lines in these regions. These flares will then trigger coronal mass ejections (CME) of lots of fast-charged particles leaving the sun. We need this to be quite strong (both speed and magnetic fields) but especially aimed just right, so that it then will hit Earth just the right way,” Brown said.

These geomagnetic storms can result in some of these solar particles being funneled toward the Earth’s upper atmosphere, specifically the ionosphere. The solar particles then collide with atoms and molecules in the Earth’s atmosphere (primarily oxygen and nitrogen), and they transfer energy to these atmospheric particles.

This extra energy excites the atoms and molecules, causing them to move to a higher energy state and glow with the bright colors characteristic of the northern lights.The specific colors of the aurora depend on which gases are being excited and at what altitude: oxygen produces green and red, while nitrogen produces blue and purple.

The more powerful the geomagnetic storm, the farther away from the poles the aurora can be seen. This is why the G5 storm on Friday led to the northern lights being visible so far and wide across the U.S. and beyond.

The ESA/NASA Solar and Heliospheric Observatory (SOHO) captured the CMEs on film as they arrived from the sun.

Only a few days after these geomagnetic storms and the aurora, the sun fired out an X8.7-class solar flare—the most powerful in nearly 20 years—causing radio blackouts across the U.S.

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