The Northern Lights could be visible in mainland US this week: NPR

In this photo from September 15, 2017, supplied by US Army Alaska, soldiers of Alpha Company, 70th Brigade Engineer Battalion, 1st Stryker Brigade Combat Team, 25th Infantry Division, based in Fort Wainwright, Alaska, perform unscheduled field maintenance under the Northern Lights on a squadron in preparation for external evaluations of the platoon at Donnelly Training Area, near Fort Greely, Alaska.

Charles Bierwirth/AP


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Charles Bierwirth/AP


In this photo from September 15, 2017, supplied by US Army Alaska, soldiers of Alpha Company, 70th Brigade Engineer Battalion, 1st Stryker Brigade Combat Team, 25th Infantry Division, based in Fort Wainwright, Alaska, perform unscheduled field maintenance under the Northern Lights on a squadron in preparation for external evaluations of the platoon at Donnelly Training Area, near Fort Greely, Alaska.

Charles Bierwirth/AP

According to the National Oceanic and Atmospheric Administration, the Northern Lights may be visible in the mainland US this week due to a strong geomagnetic storm.

The phenomenon, known scientifically as the aurora borealis, usually occurs closer to the North Pole, near Alaska and Canada.

But the storm could push the aurora lights further south on Thursday and Friday, and weather conditions permitting, could be seen in the regions of Pennsylvania, Iowa and Oregon.

What Happens During a Geomagnetic Storm?

During the storm, a coronal hole (the spots that appear black on the sun) creates high winds, which in turn trigger coronal mass ejections, or CMEs. A CME projects plasma and bits of the sun’s magnetic field into the atmosphere.

The storm started on Sunday and is expected to peak at a G3 level on Thursday — G5 is the highest measure of storm intensity — and end on Friday.

While multiple CMEs have been ejected from the sun, “most are expected to have little to no impact on Earth, but at least four have potential Earth-facing components,” according to the NOAA.

What is an aurora?

The sun’s activity is ephemeral, and in some cases the disturbances are so strong that they can pull the Earth’s magnetic field away from our planet.

But like a tight rubber band when released, the magnetic field springs back, and the force of that recoil creates powerful ripples known as Alfvén waves about 80,000 miles from the ground. As those waves get closer to Earth, they move faster thanks to the planet’s magnetic pull.

Sometimes electrons piggyback on these superfast Alfvén waves, reaching speeds of up to 45 million miles per hour as they hurtle down.

“Think about surfing,” says Jim Schroeder, an assistant professor of physics at Wheaton College who has led research on the process. “To surf, you have to paddle at the right speed for an ocean wave to pick you up and accelerate, and we found that electrons were surfing. If they moved at the right speed relative to the wave, they would be picked up and accelerated.” become.

When the electrons reach Earth’s thin upper atmosphere, they collide with nitrogen and oxygen molecules, putting them in an excited state. The excited electrons eventually calm down and give off light, which we see as the aurora.

How to view the aurora

You don’t need any special equipment to see auroras.

  • Choose a place with little light pollution.
  • If possible, go to a higher altitude.
  • Check the forecast for signs of cloud cover or precipitation, which could obscure your view.
  • Scan the sky – although north is in the name, they can appear from any direction.

NPR reporter Joe Hernandez contributed to this article.

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