Tonight’s Aurora Forecast: Northern Lights to Continue Over US

The northern lights could be visible in the U.S. as “moderate” geomagnetic storms are forecast to batter the Earth tonight, in the wake of yesterday’s “severe” storms that sparked auroras across the world.

An explosion on the surface of our sun sent a huge cloud of magnetically charged solar plasma—known as a coronal mass ejection or CME—careening towards our planet, triggering a G4-class geomagnetic storm.

As this storm hit mid-morning in the U.S., the strongest aurorae were seen rippling across Australia, further away from the South Pole than usual, and later on in the U.K. and in parts of Canada.

Today, a G2 storm is forecast to hit the Earth, which may spark the northern lights above several northern U.S. states tonight.

“The aurora may become visible over some northern and upper Midwest states from New York to Idaho,” NOAA’s Space Weather Prediction Center (SPWC) said in a forecast.

An SPWC map reveals that the northern parts of Washington, Montana, Idaho, North and South Dakota, Minnesota, Wisconsin, Michigan, New York and Maine are likely to catch a glimpse of the aurora this evening.

Geomagnetic storms are disturbances in the Earth’s magnetic field caused by a CME slamming into it. These storms are ranked on a scale of G1 to G5, with G5 being the most powerful and most rare. During these storms, the charged particles from the CME are funneled into our atmosphere along the magnetic field lines, sparking aurorae. More powerful geomagnetic storms result in aurorae being seen further away from the poles, stretching further south in the Nothern Hemisphere and further north in the Southern Hemisphere.

“Some (many?) of these particles flow earthward with significant energy along the merged fields lines,” Martin Connors, a professor of space science and physics at Canada’s Athabasca University, told Newsweek. “They crash into Earth’s upper atmosphere (height near and below the ISS) and excite particles in the atmosphere. These excited particles glow. The type of particle being hit (oxygen, nitrogen, etc) determines the color of the auroral glow.”

Red auroras are produced by high-altitude oxygen, while lower-altitude oxygen generates green light. Purple and violet colors in the aurora are produced by nitrogen molecules and atoms.

Dr. Tamitha Skov reposted an image from Esperance Airport in Western Australia of a stunning red aurora.

The G4 storm that occurred yesterday is considered “severe” on the SWPC G-scale, with G4 storms being seen around 100 times per 11-year solar cycle. G4 storms can cause voltage problems across the power grid, spacecraft issues, and disruption to satellite navigation.

“Geomagnetic field activity reached G4 (Severe) Storm Levels late in the 12-15 UTC synoptic period. Storm levels have steadily decreased over the course of the period, ending at unsettled levels,” the SWPC said in a forecast discussion.

The G2 storms forecast this evening are much less powerful. Expected about 600 times per cycle, G2 storms can result in minor voltage issues to grids at high latitudes and mild drag to spacecraft in orbit.

“Unsettled to active conditions are expected, with diminishing chances for G2 (Moderate) levels on 13 Aug as CME influences dissipate. A return to mostly quiet to unsettled levels are expected on 14-15 Aug,” SWPC said in the forecast discussion.

The most powerful geomagnetic storms, G5, are the least common of all, generally being expected about 4 times per solar cycle. However, before the May 10 storm this year that sparked aurorae across all 50 U.S. states, the most recent G5 storm had occurred in 2003.

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