The aurora borealis, also known as the northern lights, could be visible in several states this week. Original forecasts from the University of Alaska's Geophysical Institute showed 17 states could see the northern lights between July 12 to 13. Now, the forecast has changed and only a handful of states are expected to see the display, according to the institute.

The aurora borealis produces neon green waves in the night sky when electrons from space collide with atoms and molecules of the upper atmosphere of Earth, according to NASA. The result is similar to when electrons collide with neon gas to create bright lightbulbs. 

What states will be able to see the northern lights?

Last week, the University of Alaska's Geophysical Institute initially forecasted activity would be high on July 13 with visibility originally expected in Alaska, Montana, Minnesota, Wisconsin, Michigan, Oregon, Idaho, Wyoming, Nebraska, Indiana, Vermont and Maryland. The institute initially forecasted aurora activity would be high on July 12 as well, with visibility originally expected in Washington, Iowa, Illinois, Ohio and Massachusetts. 

But as of Tuesday, their forecast shows the activity status for both July 12 and 13 has been downgraded to "active" and the lights are only expected to be visible in five states; Alaska, South Dakota, Wisconsin, Michigan and Maine.

The auroras come from solar wind from the sun. Even when these winds are calm, there are auroras at some place on Earth, but they may be obstructed by clouds or sunlight, according to the institute.

The phenomenon is usually visible in Alaska, Canada, and Scandinavian countries like Greenland and Iceland during average activity. Late February to early April is usually the best time to view auroras in Alaska.

When activity increases, more U.S. states like North Dakota and Michigan have the chance to see the lights. The lights are even visible in the Southern Hemisphere in places such as New Zealand when activity is fairly strong.

CBS News has reached out to the institute for more information and is awaiting a response. 

Bryan Brasher, a project manager at NOAA's Space Weather Prediction Center explained why the forecast had changed in the past few days. A particular coronal hole had previously shown elevated activity, so forecasters like those at NOAA, expected it to do so again, he said. 

Expecting the coronal hole to produce high activity, NOAA reflected that in its 27-day outlook for the northern lights. "As this particular coronal hole rotated back into view – meaning we could see and analyze it – it was clear that it had diminished and we adjusted our forecast accordingly," Brasher told CBS News via email.

The scale for measuring these geomagnetic storms is called "the G scale," ranging from a minor storm at G1 to an extreme storm at G5. The original forecast that garnered media attention was at a G2, but NOAA recently lowered the forecast to a G1 and then lowered it again below the G scale, Brasher said.

Brasher said a G3 or a G4 storm would be needed to see the Northern Lights from mid-latitude states. "We did - for example - have a G4 storm in late March and again in late April that caused the aurora to be visible as far south as Arizona and Oklahoma," he said. 

When is the best time to look for them?

The best time to see the lights is when the sky is clear and dark, according to the institute. They are more visible closest to the equinox, or the longest days of sunlight in the year occurring in the spring and fall. Auroras come from solar storms. 

The National Oceanic and Atmospheric Administration has an animated forecast of the lights' movement and says the best time to see them is within an hour or two of midnight, usually between 10 p.m. and 2 a.m. local time.

NASA's Parker Solar Probe, which is on a mission to the sun, recently gathered information on the solar storms that create the aurora borealis. Solar winds travel 93 million miles to Earth's atmosphere, where the bursts evolve into a "homogeneous, turbulent flow of roiling magnetic fields intertwined with charged particles that interact with Earth's own magnetic field and dump electrical energy into the upper atmosphere." 

This creates stunning aurora in the sky – but the lights can also wreak havoc on communications systems. In 1859, the Carrington Event – a strong solar eruption that made the auroras extremely bright and long-lasting – knocked out telegraph and electrical systems, according to the University of Chicago.

The sun's creation of powerful solar winds is on an 11-year cycle and the next peak in the activity is expected around 2025. Auroras will likely be easier to see at lower latitudes during this time, according to the institute. 

In:
• Aurora Borealis
• Northern Lights

Caitlin O'Kane

Caitlin O'Kane is a digital content producer covering trending stories for CBS News and its good news brand, The Uplift.

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