HOW SOLAR RADIATION STORMS ARE CLASSIFIED

50 per 11-year solar cycle

A minor solar radiation storm causes minimal impact on highfrequency (HF) radio in the polar regions, but otherwise causes no damaging effects.

25 per cycle

A moderate storm affects navigation at the polar caps and may, in rare instances, cause problems in satellites, but poses no threat to humans.

10 per cycle

During a strong storm, astronauts are advised to seek shelter, while satellites could lose power and instrument usage. HF radio will degrade at the poles.

3 per cycle

Astronauts and passengers on planes may be exposed to radiation, while satellites could experience orientation problems. HF radio blacks out at the poles.

Less than 1 per cycle

Astronauts and aeroplane passengers exposed to high radiation. Satellites may be rendered useless. HF communications black out in polar regions.