The Aurora Borealis or Northern Lights is considered one of the most awe-inspiring sights that can be viewed on Earth. An ethereal display of color in the night sky, it has been accorded varied supernatural powers by diverse indigenous peoples.
Although there are also Southern Lights—termed Aurora Australis—these are less included in folklore, since fewer people reside in the Southern regions where they are apparent. Around the North Pole, the auroral zone extends as a radial belt encompassing around 2,500 miles, and its primary latitude is described as 56-69 degrees North.
Solar Flares – The Cause of Northern and Southern Lights
Storms on our Sun periodically cause the eruption of solar flares and coronal mass ejections. In turn, the released ions, electrons, protons and the like—as well as radiation—travel through space, and can strike the Earth’s magnetic field.
It is this engagement with the neutral atoms in the Earth’s atmosphere—and subsequent traveling along the Earth’s magnetic field—that causes the magnificent display of wavy colors in the night sky.
Impact on Earth’s Electrons of Coronal Mass Ejections
In the Earth’s atmosphere, stricken neutral atoms’ electrons move to higher-energy orbits, which is further away from its nucleus (excitement phase). Then, when an electron moves back to its lower-energy orbit, it releases a photon or particle of light (relaxation phase).
It is this relaxation phase that lights up the sky with its Aurora displays near each of the Earth’s poles. Meanwhile, atoms in the Earth’s gasses that are re-radiated (excited) determine the colors displayed in the Northern and Southern lightshow.
If the solar eruption comes from a sunspot group located near the center of the earth-facing solar disk, then chances are high that the coronal mass ejection will strike the earth’s atmosphere, according to the SpaceWeatherLive website.
Meanwhile, the intensity bell curve of the sun’s coronal mass ejections corresponds to an 11-year period. Therefore, every 11-year period, there is a particularly spectacular Aurora Borealis observed.
Three Solar Factors Required for Occurrence of Auroras
The following are three solar factors affecting whether an Aurora Borealis (or Aurora Australis) will occur. These are:
- Duration of the solar flare;
- Size of the plasma cloud;
- Speed at which coronal mass ejection has departed the Sun’s atmosphere
Best Locations for Viewing Northern and Southern Lights
Alaska is the only state in the US where the Aurora Borealis can be regularly witnessed. Outside of the United States, the Northern Lights frequently can be viewed in:
- Northern Canada;
- Scandinavian countries (g., Norway, Denmark, and Sweden)
- Northern Siberia
However, Northern Lights can also be viewed in other areas that are at an altitude of at least 80 km. The best viewing of the Aurora Borealis is typically from January to March, according to the AuroraZone website.
Colors of the Northern versus Southern Lights
The focus of a PBS television episode of NOVA was devoted to the Northern and Southern Lights on February 1, 2017, and presented striking views of the Aurora Borealis and Aurora Australis in various countries. While the colors are typically green in the Northern regions, they are more reddish in color in the Southern regions. However, colors can also be pink, yellow, and violet—and occasionally even orange or white.
Specific atmospheric gasses in tandem with their Aurora-related colors are as follows:
- Oxygen: causes greenish color.
- Nitrogen: causes reddish or bluish colors.
For scientists unable to observe the Aurora Borealis in person, development of the Planeterella machine enabled the re-creation of this natural lightshow in a Langley Research Center lab, per a NASA report!