Definition
A natural light display in the upper atmosphere, caused by charged particles from the sun striking gas molecules in the Earth's ionosphere. Auroras occur most often near the magnetic poles and can disrupt high-frequency (HF) radio communications and degrade the accuracy of magnetic compasses and some navigation systems during periods of strong solar activity.
Plain English
The northern and southern lights -- coloured glows in the sky near the poles caused by the sun's energy hitting the upper atmosphere. For pilots, strong auroras can mess with radios and navigation equipment.
Context Anchor
Pilots may see an aurora during night flights in high-latitude areas, such as Alaska, Canada, or northern Europe, or hear it mentioned in route or space-weather briefings.
Derivation
From the Latin Aurora, the Roman goddess of dawn. The name was given because the glow in the sky resembles the colours of sunrise. Knowing this helps pilots remember it is a light phenomenon, not a weather or atmospheric pressure event.
Why Pilots Care
Strong aurora activity can interfere with high-frequency radio communications and some navigation signals.
Analogy
It can look like a slow-moving curtain of light hanging in the sky.
Grounding Statement
On a dark northern night, an aurora may appear as green, red, or purple light shimmering above the horizon.
Intuition Check
An aurora is not dawn, lightning, or city light. It is a natural glow high in the atmosphere caused by activity from the Sun.
Example Sentence 1
The crew flying a polar route was advised that a strong aurora was expected to disrupt HF communications for several hours.
Example Sentence 2
Dispatch warned of possible HF radio fade due to aurora activity that night.