What causes aurora borealis? The science behind the otherworldly light show
Everything you need to know, including the best time and place to see the Northern Lights.
Auroras hover over our skies with tantalizing displays of light and color that seem otherworldly. But the real science behind the Northern Lights is as fantastic as the fantasy.
So here’s the science behind this natural phenomenon so you’ll have the best chance of seeing these breathtaking light displays.
What are auroras?
Auroras are colorful light displays in the sky caused by the coupling of the Sun’s violent discharges and Earth’s atmosphere.
Perhaps the most famous aurora is the Northern Lights, also known as aurora borealis. The Northern Lights shine across northern latitudes and can be typically seen in Northern Canada, Alaska, Northern Europe, and Russia.
However, the Northern Lights aren’t the only cosmic fireworks show. If you are in the southern hemisphere close to the South Pole, you might catch sight of its sister aurora, the aurora australis, or the Southern Lights.
Other planets experience auroras as well. Within our solar system, Jupiter, Saturn, Uranus, and Neptune also experience auroras, while aurora-like phenomena created by slightly different forces have been spotted on Mars.
What causes auroras?
When the Sun emits charged particles in the form of solar wind into space, some of them make their way towards our planet. As they go through Earth’s magnetic field, they get funneled into the planet’s atmosphere through the northern and southern poles.
Once they enter Earth’s atmosphere, the particles excite oxygen and nitrogen atoms in Earth’s ionized upper atmosphere, which causes them to light up in these varying, beautiful colors.
When is the best time to see aurora?
The month of March typically experiences enhanced space weather conditions, with increased geomagnetic activity in the spring and autumn seasons.
The reason? Earth tilts away from the Sun during winter and toward the Sun during summer. Earth's axis tilts by 23.5 degrees, but during the equinoxes — the beginning of the spring and fall seasons — the Earth is perpendicular to the Sun.
During the spring equinox, which falls on March 20, the Earth is almost upright toward the Sun. As a result, the Sun’s particles have a better chance of reaching the Earth during that time.
Earlier this month, aurora sightings were reported in Canada and Scotland.
However, the intensity and frequency of the aurora largely depend on the activity of the Sun, which is controlled by its solar cycle. The Sun’s magnetic field goes through a periodic cycle in which the south and north poles essentially switch spots, taking another 11 years or so for them to switch back.
It is still difficult to predict space weather, and anticipate when the Sun flares up with solar activity, but things generally start to heat up midway through the solar cycle. The new solar cycle, cycle 25, began in December 2019.
Although the aurora itself is not harmful to Earth, the Sun can create intense solar storms that can disrupt our communication infrastructure and power grids.
Where can you see auroras?
Auroras can be seen from both the southern and northern hemispheres, preferably somewhere with a higher vantage point and low light pollution.
Some of the more famous places where people flock to see auroras every year are Iceland, Norway, Canada, Alaska, Greenland, Finland, New Zealand, and Sweden. They’re rare — but not unheard of — in the continental United States under the right conditions.
You can visit the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center where they run an aurora forecast to know your chances of catching these stunning lights.