The aurora is a natural light display that occurs in the Earth's upper atmosphere, typically in the polar regions. In the northern hemisphere it is known as the Aurora Borealis (or Northern Lights) whilst in the Southern Hemisphere it is known as the Aurora Australis (or Southern Lights).

One of the most incredible aspects of the aurora is the variety of colors that it can display, ranging from pale greens and yellows to deep reds and purples. In this article, we will explore the scientific explanation for the different colors of the aurora.

The aurora itself is caused by the interaction between charged particles from the sun (which occur during an ejection) and the Earth's magnetic field. These particles, known as the solar wind, are funneled towards the poles by the Earth's magnetic field, where they collide with atoms and molecules in the upper atmosphere. This collision causes the atoms and molecules to become excited, releasing energy in the form of light.

The Aurora Australis over Kilcunda, Victoria, Australia.

The specific colors of the aurora are determined by the types of atoms and molecules that are present in the upper atmosphere, as well as the energy of the solar particles. Some of the colors and the molecules that cause them are listed below:

  • Oxygen creates a red to orange or a yellow to green color
  • Nitrogen creates a deep red glow, but when ionised it creates a deep blue to purple color.
Star Trails and the Aurora Australis
Some Red / Pink Aurora beams captured in a timelapse showing star trails at Pyramid Rock at Phillip Island, Victoria, Australia.

The exact colors and intensity of these aurora can also depend on the specific conditions in the atmosphere. For example, a higher concentration of oxygen will result in a stronger green or yellow light. Additionally, the energy of the solar particles can also affect the intensity of the aurora. More energetic particles will result in a brighter, more intense auroral display.

So there you have it, the different colors of the aurora are caused by the interaction between charged particles from the sun and the Earth's upper atmosphere. The specific colors are determined by the types of atoms and molecules present in the upper atmosphere, as well as the energy of the solar particles. The aurora is a truly mesmerizing display of nature, and understanding the science behind it can enhance our appreciation of this beautiful phenomenon.

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