Auroras and space weather: what they are and how to see them

Updated November 2026

Auroras are glowing curtains of light made when particles from the Sun, steered by Earth’s magnetic field, crash into the upper atmosphere near the poles. They are most common in a ring around each magnetic pole, and big solar storms can push them far toward the equator.

What auroras are

The Sun constantly sends out energy and charged particles. Some of them get caught in Earth’s magnetic field and are guided toward the polar regions. There, NOAA’s Space Weather Prediction Center (SWPC) explains, fast-moving electrons collide with oxygen and nitrogen atoms and molecules in the upper atmosphere, and those collisions give off light. Auroras typically form 80 to 500 km above the ground, far higher than airplanes fly.

In the north the lights are called the aurora borealis or northern lights; in the south, the aurora australis or southern lights. Their colors depend on the gas: NASA notes that oxygen gives off green and red light, while nitrogen glows blue and purple.

The auroral ovals

Earth’s magnetic field shapes the aurora into two ovals, roughly centered on the north and south magnetic poles. The best viewing zone lies between about 60 and 75 degrees latitude, where an aurora can be seen on more than half of the nights in a year (SWPC). During major storms, the ovals expand toward the equator.

Solar cycle 25

The Sun’s activity rises and falls on a cycle of roughly 11 years, as its magnetic poles flip. The Solar Cycle 25 Prediction Panel announced that the solar minimum that started cycle 25 occurred in December 2019. On October 15, 2024, NASA, NOAA and the panel announced that the Sun had reached its solar maximum period.

A few events from this maximum:

In October 2024 NASA said the maximum phase would likely last another year or so before the Sun entered its declining phase. The exact peak can only be confirmed after scientists have tracked a steady decline in activity, which may take months or years. Strong storms can still happen as activity falls, so check SWPC’s Solar Cycle Progression page for the latest sunspot numbers.

The Kp index and storm scales

The Kp index measures how disturbed Earth’s magnetic field is. It runs from 0 to 9 and is based on the largest swings recorded by magnetometers over each three-hour period, averaged from 13 observatories between 44 and 60 degrees geomagnetic latitude. A Kp of 1 is calm; 5 or more means a geomagnetic storm.

NOAA geomagnetic storm scale (SWPC)
LevelKpWhere aurora has been seen (US examples)Storm events per cycle (average)
G1 Minor5Northern Michigan and Maine1,700
G2 Moderate6New York and Idaho600
G3 Strong7Illinois and Oregon200
G4 Severe8Alabama and northern California100
G5 Extreme9Florida and southern Texas4

SWPC gives a rule of thumb: at Kp 0 the equatorward edge of the auroral oval sits at about 66 degrees geomagnetic latitude, and it moves about 2 degrees closer to the equator for each step in Kp. So at Kp 5 the edge is near 66 − (2 × 5) = 56 degrees. Geomagnetic latitude is measured from the magnetic pole, so it differs from the latitude on a map. Bright auroras can also be seen hundreds of kilometers away from where they actually occur.

When and where to look

Southern lights. The aurora australis forms the same way. SWPC’s 30-minute forecast has a separate map for the Southern Hemisphere.

Check yourself

Why are auroras mostly seen near the poles?

Earth’s magnetic field guides charged particles toward the magnetic poles, so auroras form in ovals around them. Only strong storms push the ovals toward the equator.

What does a green aurora tell you?

Green light comes mainly from oxygen in the upper atmosphere. Nitrogen gives blue and purple tones.

Using SWPC’s rule of thumb, where is the edge of the auroral oval at Kp 7?

66 − (2 × 7) = 52 degrees geomagnetic latitude. That is close to the level of a G3 storm, when auroras have been seen as far south as Illinois and Oregon.

Sources