Mississippi State University Weather

Painting the Sky: The Northern Lights

The Northern Lights are a natural phenomenon that occurs at high latitudes around the Earth’s poles, however earlier this week the beautiful light show was on display in parts of the United States. This is an extremely rare occurrence for us in the continental United States, but portions of the Northeast and Midwest were able to experience this magnificent event Monday and Tuesday nights. The lights were driven south to lower latitudes all due to mass solar eruptions that triggered a geomagnetic storm. With the timeliness of this spectacular event, what better topic to explore in this week’s blog than the Northern Lights! 

What are the Northern Lights?

This mystifying natural phenomenon is also known as Aurora Borealis. The Northern Lights mainly occurs at the poles in both the Northern and Southern hemispheres. Collisions between electrically charged particles cause the sky to illuminate in an array of colors. The lights can extend 50 to 400 miles above the surface and take many forms, such as scattered clouds of light, arcs, or shooting rays.

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Image Credit: NASA Aurora Image Gallery https://www.nasa.gov/mission_pages/sunearth/aurora-image-gallery/index.html

What Causes this Phenomenon?

The basic explanation for the Northern Lights is the collision between particles in the atmosphere and particles from the sun, but lets dive into a little more detail. This process originates 93 million miles away, when storms on the sun cause gusts of charged solar particles to be released into space. These particles are blown towards Earth by the solar winds and are mainly deflected by the Earth’s magnetic field. Keep in mind, the magnetic field is weaker at the poles, so at this location some particles are able to enter the Earth’s atmosphere. The positive charged particles (electrons) from the sun collide with gaseous particles within the upper level of the atmosphere, causing the particles to become ‘excited’.  Finally, as the molecules return to their original state, they emit photons, or small bursts of energy in the form of light.

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Image Credit: EarthSky via NASA

What Causes Different Colors?

Variations in color are due to the type of gas particles, Oxygen or Nitrogen, that collide with the particles from the sun as well as the altitude at which they collide. The most common auroral color is green and is produced when oxygen molecules collide with electrons about 60 miles above the surface. More rare, all red auroras are produced by high altitude oxygen molecules 200 miles above the Earth’s surface. Finally, when Nitrogen collides with the electrons, it produces light that has a blue or purple coloring.

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Image Credit: NASA Aurora Image Gallery

https://www.nasa.gov/mission_pages/sunearth/aurora-image-gallery/index.html

When and Where Can You See the Northern Lights?

 The Northern Lights typically occur in a ring shaped area, known as the auroral ovals, around the magnetic poles. A few of the best places to view the lights are in central Alaska, Canada, Greenland, and northern Russia. Although auroral activity can occur day or night, the light is much dimmer than sunlight making it virtually impossible to see during the daytime. The best displays take place when it is dark, specifically a few hours before midnight. It’s also easier to see the Northern Lights in the winter due to the long periods of darkness and high frequency of clear nights.

~Kelly Scott

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Citations:

 “Aurora.” nasa.gov. NASA, n.d. Web. 5 Nov. 2015.             <http://pwg.gsfc.nasa.gov/polar/EPO/auroral_poster/aurora_all.pdf>.

 “Aurora Image Gallery.” nasa.gov. NASA, n.d. Web. 05 Nov. 2015.     <https://www.nasa.gov/mission_pages/sunearth/aurora-image-gallery/index.html>.

 “What Causes the Aurora Borealis or Northern Lights? | EarthSky.org.” EarthSky. N.p., 30 Jan. 2015. Web. 05 Nov. 2015.<http://earthsky.org/earth/what-causes-the-aurora-borealis-or- northern-lights>.