The Aurora Borealis, more commonly known as the Northern Lights, is a dazzling natural light display that occurs in the Earth’s sky. This phenomenon can be seen in high latitude regions like Alaska, Canada, Iceland, Norway, Sweden, Finland, and Russia. The Auroras are the result of collisions between gaseous particles in the Earth’s atmosphere and charged particles released from the Sun’s atmosphere.
These collisions cause the gaseous particles to light up. The color of the Aurora depends on which gas is colliding with the charged particles. The most common Auroral color, a pale yellowish-green, is produced by oxygen molecules located about 60 miles above the Earth. Rare, all-red Auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora.
The colors can also be affected by the altitude of the collisions. At higher altitudes above the Earth, more oxygen produces reds and greens. At lower altitudes, the increased concentration of nitrogen produces more purple and blue hues.
What Do the Most Common Aurora Colors Mean?
Here is an overview of some of the most common Aurora colors and what they indicate about the composition of the atmosphere where the collisions are occurring:
Green
The most common color of the Aurora is a pale, yellowish-green. This is produced by collisions with atomic oxygen roughly 60 miles above the Earth’s surface.
Red
A deep, blood red Aurora indicates collisions with atomic oxygen occurring very high in the atmosphere, up to 200 miles in altitude. The red color is very rare compared to the more common green Auroras.
Blue
A blue or purple Aurora indicates that nitrogen gas is colliding with the charged particles around 60 miles above the Earth. The blue color is caused by the nitrogen molecules gaining energy and becoming excited.
Pink
Soft pink Aurora indicates a mix of collisions with both oxygen and nitrogen at lower altitudes, creating a mix of green and red or blue colors.
Yellow
A creamy yellow or pale lemon colored Aurora is created by a mix of colliding oxygen and nitrogen gases. The nitrogen moderates the yellowish-green of oxygen to create a paler yellow.
Rarer Aurora Colors and What They Mean
Less common Auroral displays can also occur under certain atmospheric conditions. Here are some of the more unusual Aurora colors and what they signify:
Orange
Orange Auroras indicate a combination of colliding oxygen and nitrogen at lower altitudes, below 60 miles high. The nitrogen moderates the red oxygen to create an orange hue.
Violet
A vivid violet Aurora can form when charged particles collide with trace amounts of neon gas atoms. Neon emits a brilliant violet glow when excited.
White
A shimmering white Aurora is created when all the colors of the visible spectrum mix together at lower altitudes. This effect requires a combination of oxygen, nitrogen, and other gases all colliding simultaneously.
Altitude Differences in Aurora Colors
The altitude where the particle collisions occur also affects the resulting color of the Aurora. Here is an overview of how altitude impacts the color:
- Above 150 miles: Mostly red Auroras from oxygen collisions
- 100 – 150 miles: Mix of red and green from oxygen
- 60 – 100 miles: Mostly yellowish-green from oxygen
- Below 60 miles: Purples, blues and violets from nitrogen
As you can see, higher altitude collisions tend to produce red, while lower altitudes yield more blue and purple colors. The most common green yellow Auroras occur in the middle altitudes around 60 miles high.
Aurora Color Intensity
The intensity and vibrancy of the Aurora is driven by the amount of energy being transferred by the collisions. More energetic collisions produce brighter, more vivid colors. So a deeper red Aurora indicates higher energy oxygen collisions than a pale pink Aurora. Here are some intensity guidelines:
- Pale, wispy colors indicate lower energy collisions
- Bright, vivid colors signify higher energy collisions
- Steady, constant colors mean sustained collision activity
- Quickly shifting colors suggest rapid changes in particle flows
More intense geomagnetic storms tend to produce brighter, more colorful Auroral displays. The intensity of the colors provides clues to the types of atmospheric interactions occurring to create the dazzling lights.
Conclusion
The amazing colors of the Northern Lights carry a significant amount of scientific information about what’s happening in the high atmosphere. Each hue contains clues about the gases, altitudes, energies, and variables that came together to produce the Aurora.
Green indicates lower altitude oxygen, while red signifies high altitude oxygen. Blue and purple point to nitrogen at lower altitudes. More intense colors signal greater collision energies, while paler colors mean less activity. Understanding what the colors signify allows us to unlock the complex dynamics of our atmosphere.
So next time you gaze up at the magical Auroral light show, remember the meaning behind the magnificent colors dancing across the sky. It just adds another layer of wonder to one of nature’s most incredible displays.
Data Table of Aurora Colors and Altitudes
| Aurora Color | Cause | Altitude |
|---|---|---|
| Green | Oxygen | 60 miles |
| Red | Oxygen | Up to 200 miles |
| Blue/Purple | Nitrogen | 60 miles |
| Pink | Oxygen + Nitrogen mix | Lower altitudes |
| Yellow | Oxygen + Nitrogen mix | Varies |
| Orange | Oxygen + Nitrogen mix | Below 60 miles |
| Violet | Neon | Varies |
| White | Full spectrum mix | Lower altitudes |
