Aurora borealis green sky

The aurora borealis, a display of green lights in the sky, occurs when solar particles collide with Earth's atmosphere, creating luminous curtains visible at high latitudes.

About this subject

The aurora borealis, also known as the northern lights, is a natural phenomenon that captivates observers near the Arctic Circle. This light show occurs when charged particles from the solar wind interact with Earth's magnetic field and atmospheric gases, such as oxygen and nitrogen. When these particles excite oxygen atoms at altitudes between 100 and 300 kilometers, they emit a characteristic green light, the most common auroral color. Other colors, like red, blue, or purple, appear at different altitudes or with different gases, but green dominates due to its frequency.

The best time to view the aurora borealis is during winter, from September to March, with long, dark nights. Prime locations include northern Scandinavia, Canada, Alaska, and Iceland. The phenomenon has a rich cultural history: Nordic peoples believed it was light reflected from the shields of the Valkyries, while Inuit saw it as the souls of the dead dancing in the sky. In modern science, studying the aurora helps understand solar activity and space weather, which can affect satellites and power grids.

Fun fact: the aurora borealis has a counterpart in the Southern Hemisphere called the aurora australis. Both occur simultaneously, but the northern lights are more famous due to easier access for tourists. In 2024 and 2025, the solar cycle reached its maximum activity, producing exceptionally intense auroras visible even at mid-latitudes, such as the northern United States and, rarely, southern Brazil.

Frequently Asked Questions

What causes the green color in the aurora borealis?

The green color is produced by the excitation of oxygen atoms at altitudes between 100 and 300 km. When solar particles collide with these atoms, they release energy as green light, the most common auroral emission.

When is the best time to see the aurora borealis?

The ideal period is between September and March, during winter in the Northern Hemisphere, when nights are long and dark. Auroral activity is also stronger around the fall and spring equinoxes.

Can the aurora borealis be seen in Brazil?

It is extremely rare but possible during very strong solar storms. In 2024, an aurora was recorded at low latitudes, including southern Brazil, due to the solar maximum.