Aurora Explained: What Creates the Northern and Southern Lights?

A beginner-friendly explanation of auroras, solar activity, Earth's magnetic field, and why the sky can glow green, red, and purple.

Auroras are glowing displays in Earth’s upper atmosphere. In the Northern Hemisphere they are called aurora borealis, or northern lights, while in the Southern Hemisphere they are called aurora australis, or southern lights.

Why this matters: Auroras are a visible sign of the connection between the Sun, Earth’s magnetic field and the upper atmosphere.

Main triggerCharged particles and disturbances from the Sun

Where they glowHigh in Earth’s upper atmosphere

Common colorsGreen, red, blue and purple

Best-known regionsHigh latitudes around the magnetic poles

Where auroras begin

Auroras begin with the Sun. The Sun continuously releases charged particles in the solar wind. Solar flares and coronal mass ejections can intensify conditions in near-Earth space and help trigger stronger geomagnetic activity.

Real green aurora photographed from the International Space Station in 2023 — A real aurora photographed from the International Space Station in February 2023. Credit: NASA/ISS Crew Earth Observations.

Earth's magnetic field does the guiding

Earth’s magnetic field deflects much of the charged-particle flow, but energetic particles can be guided toward the polar regions. When they enter the upper atmosphere, they collide with oxygen and nitrogen atoms and molecules.

Those collisions transfer energy to atmospheric gases. When the gases release that energy, they emit light.

Why auroras have different colors

Green is the most common auroral color and is usually associated with excited oxygen at particular altitudes. Higher-altitude oxygen can produce red light, while nitrogen can contribute blue, purple and pink shades.

The exact color depends on altitude, atmospheric composition and the energy of the incoming particles.

NASA satellite observation showing auroral activity over North America — A NASA/NOAA satellite observation of auroral activity over North America, showing that auroras can also be monitored from orbit.

Why auroras are usually seen near the poles

Earth’s magnetic field funnels charged particles toward high latitudes, forming auroral ovals around the magnetic poles. During stronger geomagnetic storms, those ovals can expand and auroras may become visible much farther from the poles.

Can auroras affect technology?

The lights themselves are not the main technological hazard, but the same space-weather disturbances that create intense auroras can affect radio communications, navigation systems, satellites and, in severe cases, electrical grids.

Simple takeaway: An aurora is the visible result of solar particles interacting with Earth’s magnetic field and upper atmosphere.

FAQ

Are northern and southern lights the same phenomenon?

Yes. Aurora borealis occurs in the north and aurora australis in the south, but both are produced by the same basic Sun–Earth interaction.

Why is green the most common aurora color?

Green light is commonly emitted by excited oxygen at altitudes where many visible auroras form.

Can auroras appear far from the poles?

Yes. Strong geomagnetic storms can expand the auroral ovals toward lower latitudes.