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What Causes the Northern Lights? | Aurora Borealis & Australis | The Old Farmer's Almanac

What Are the Northern Lights?

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Aurora Borealis: Nature's Light Show

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Spring is aurora season! Commonly called the “northern lights,” auroras appear as green shimmering curtains of light dancing across the night sky. Learn more about nature’s light show—and why auroras appear near the equinoxes!

Auroras, also known as the polar lights, are natural light displays in the Earth’s sky. Because of Earth’s magnetic field, auroras are most often seen in the high latitudes, near the poles. They can appear as curtains of light moving across the entire sky and sometimes appear as huge arcs and pillars of color that dance and float through the dark.

  • In the Northern Hemisphere, the event is called the aurora borealis, which means “dawn of the north,” or the northern lights.
  • In the Southern Hemisphere, it is called the aurora australis, which means “dawn of the south,” or the southern lights.

Even the names are beautiful! 

How are the Northern Lights Formed?

Auroras are actually caused by the Sun and solar activity.

  • The Sun is very stormy, constantly sending out solar flares and high-energy charged particles that travel at speeds of up to a million miles per hour.
  • “Solar wind” is made up of streams of these particles. As a strong solar wind gust enters the Earth’s magnetic field and collides with gases in the upper atmosphere, the gases begin to glow in a variety of colors;
  • Auroras often start with a green glow. You could see shades of green, red, yellow, purple, and blue. The colors depend on the energy level of each gas particle and which gas particles are present.
  • The movement is also beautiful. When the solar winds ripple through the magnetic field, the curtains of light appear to dance, brighten, or fade.

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One of the most colorful auroras in recent history occurred in March 1989. It was visible in Canada and the United States and as far south as Mexico. The electrical surge that accompanied it was so strong that parts of Canada were blacked out all night!

Aurora borealis as seen from the International Space Station (ISS)
The aurora borealis as seen from the International Space Station (ISS).

When to See Auroras

While auroras are triggered any time by strong solar activity, the traditional aurora-watching season is during the weeks before and after the spring and autumnal equinoxes, when we transition seasons.

  • Why? According to NOAA, the times around the equinoxes are when the Earth is affected more directly by the Sun’s geomagnetic storms, which cause disturbances in Earth’s magnetic field. It seems to be related to the Earth’s orbit around the Sun and the position of our planet’s magnetic poles at a given time of year.

The best time of the day to spot auroras is late at night or in the early morning (from 10:00 P.M. to about 3:00 A.M.) Look north on a clear, moonless night from a dark place away from city lights.

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Where Can You See the Northern Lights?

The auroras occur at high latitudes so aurora fans will even travel to Alaska or Norway to see the sight on a tour. However, if you live in Canada or the northern tier states (Maine, Michigan, etc.), you are likely to see the northern lights if you make an effort. Occasionally, due to a massive solar storm, the Lights will occasionally make it further south.

Some Web sites such as spaceweather.com will report on solar explosions and forecast upcoming auroras. NOAA Space Weather Prediction Center also reports on solar flare activity.  If you have a shortwave radio or have a CB radio, any disturbances or skips are also a telltale sign.

That night, the next night, and even the next, get out away from city lights and look up toward the north.

Aurora Borealis

Fun Facts About the Northern Lights

  • No two light shows are ever the same.
  • The most common colors are green and pink, but the aurora may also appear purple, red, blue, or yellow.
  • A single active display can produce one trillion watts of electricity.
  • Some people claim they have heard the northern lights hiss and crackle.

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If you ever get a chance to see nature’s light show, don’t miss this spectacular opportunity!

Have you ever seen the aurora borealis (or aurora australis)? What was it like in person? Tell us in the comments below!

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