Author: Zoya Farooqui
From: McKinney, Texas, USA
Image Credit: Farmers’ Almanac
It is legend that the pot of gold lies at the end of the rainbow, but the real treasure lies at the tips of the earth. If you are lucky enough, you may catch a glimpse of these dancing lights at the right place and time. Although the term aurora seems mythical, it is merely the product of a simple science phenomenon.
What Causes Auroras?
Auroras are the effect of the interaction between the earth and the sun. Electromagnetic radiation and highly energized particles that are emitted by the sun continuously into space create space weather. Part of this space weather is solar wind, which is made of energized particles (mostly protons and electrons) that travel at high speeds and high temperatures.
The earth’s role in creating auroras is played by its magnetic field, which stretches from its core to areas in space where solar winds travel. The region in which earth’s magnetic field and the solar winds meet is called the magnetosphere. The magnetosphere protects our planet from solar winds and harmful cosmic rays. However, with the right conditions, some particles enter the earth’s atmosphere and interact with gas molecules and atoms, which releases lights known as auroras.
Colors and Shapes
The colors of the lights released can vary depending on a variety of factors, including the kind of gas molecules, their electrical state at the time of collision, the altitude at which they are at, and the type of the solar wind particles they collide with.
1. Colliding particles
Oxygen: yellow, green
Nitrogen: red, blue, purple
Mix of gases: multi-colored
2. Type of collision
Atomic nitrogen: blue
Molecular nitrogen: purple
Up to 150 miles high: green
Above 150 miles: red
Up to 60 miles: blue
Above 60 miles: purple, violet
The shape of auroras can be categorized as curtains, bands, veils, coronas, patches, or rays. Although scientists are still trying to pinpoint exactly what causes these different shapes, they know that it depends on where the electrons came from and what caused them to enter the atmosphere. Due to the fact that particles from solar winds continuously enter the atmosphere, auroras can be static or dynamic, appearing with different shapes and colors, sometimes even pulsating in the sky.
Northern and Southern Lights
Since the solar wind particles enter the atmosphere at the poles, auroras are best seen at the Arctic and Antarctic circles. In the Arctic Circle, they are known as aurora borealis or the northern lights, while in the Antarctic Circle they are called aurora australis or the southern lights. Although the southern lights are difficult to view, the northern lights can be seen from Alaska, Canada, and sometimes even from Sweden, Finland, and Norway. In rare events, they are even spotted further south. Even though these lights are present throughout the year, it is best to view them during the winter months due to longer periods of darkness. Moreover, auroras are known to be even brighter after high sunspot activity.
Until now there is no way to efficiently predict an aurora sighting. Although some agencies such as NASA track auroras, it is nearly impossible to predict them, which makes their viewing even more special. If you ever come across the northern lights in your lifetime, be sure to capture them on camera. Auroras may seem dim because the redder lights are difficult for human retinas to pick up. However, with a long-exposure setting, cameras, being more sensitive, are capable enough to capture auroras’ vibrant colors.
About the Author: Zoya Farooqui
Zoya is a rising junior in high school who loves art, podcasting, programming, robotics, and spending time with her friends and family. When she’s free, she enjoys playing video games and listening to music.