Geomagnetic Storm Triggers Spectacular Aurora Across U.S. States

A geomagnetic storm whipped up above the U.S. last night as solar winds slammed into the Earth's atmosphere, sparking a gorgeous display of glowing lights in the sky.

During the September 18 G2-level storm, spectacular ripples of the Northern Lights were seen above several northern U.S. states, including Minnesota, Wisconsin, Wyoming and Montana.

Traces of the aurora were even visible on camera as far south as Nebraska, according to spaceweather.com.

green northern lights
The aurora borealis, also known as the northern lights, illuminates the sky in southeastern Iceland on October 7, 2018. The stunning light display was visible from several U.S. states on September 18. Photo by MARIANA SUAREZ/AFP via Getty Images

Geomagnetic storms are classed on a scale from G1 (minor) to G5 (extreme), making a G2 storm the second level of severity. They are usually caused by coronal mass ejections from the sun, also known as CMEs, which is when huge plumes of solar plasma and magnetism are flung out from the sun's surface due to realigning magnetic fields. This solar wind then travels out into space, occasionally in the Earth's direction, at immense speeds of up to 6.7 million miles per hour.

The CME then slams into the Earth's magnetic field and ionosphere, where it interacts with gas molecules and causes strange effects, including the aurora.

"A geomagnetic storm is the alteration of the Earth's magnetic environment. This means when the magnetic fields that usually surround our Earth start to be distorted," Daniel Brown, an associate professor in astronomy and science communication at the U.K.'s Nottingham Trent University, previously told Newsweek.

"Stronger storms will impart more energy on the electrons in our Earth's magnetic environment or magnetosphere," Brown said. "These electrons are then going to be the source of the light seen in southern/northern lights, as they crash into oxygen or nitrogen in our high atmosphere, making them glow. The more energetic the electrons are, the brighter the display."

northern lights
The northern lights on March 9, 2018, in Norway. They were visible in several U.S. states on September 18. OLIVIER MORIN/AFP via Getty Images)

G2 storms usually occur about 1,700 times per 11-year solar cycle, according to NASA's G-scale. The stronger the storm, the less common, and the further away from the poles the effects of the northern lights: G5 storms can cause an aurora to be visible as far south as Florida, or up into Australia.

"The colors in the aurora are the result of particles in the upper atmosphere becoming excited by collisions with particles coming from within the magnetosphere and some from within the solar wind," Brett Carter, an associate professor in space science at RMIT University in Australia, told Newsweek earlier this year. "The different colors are the result of electrons relaxing from different energy levels from oxygen (the most common reds and greens) and nitrogen (dark reds/blues)."

Therefore, the further south an observer is, the more red the northern lights will appear, as they will only be able to spot the fainter red hues being emitted from higher-altitude oxygen.

red aurora
Northern lights showing green and red light in Finland in January 2018. They were visible in parts of the U.S. on Septmeber 18. Photo by Philippe Bourseiller/Getty Images

"That red color is usually also rather faint since you do not have that many of the oxygen atoms around at such high altitudes," Brown told Newsweek in February. "But, if you have a strong enough activity like we are getting now, there are enough exciting particles in the coronal mass ejections to interact with more oxygen and make the red brighter."

This is why there was a faint red aurora over Nebraska, which was only visible using a camera.

Geomagnetic storms can also have other effects on the planet, including issues with the power grid.

"These storms can influence more than just the power grid infrastructure," Carter said. "The use of GPS can be impacted due to variations in the ionosphere, and the orbits of satellites in low-Earth orbit experience increased atmospheric drag due to the swelling of the upper atmosphere."

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about the northern lights? Let us know via [email protected].

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