The most energetic particles of all, created by solar flares, can reach the Earth in just 30 minutes. This activity is particularly noticeable at times of solar maximum. When charged particles from the Sun enter the Earth's upper atmosphere, they create shimmering curtains of coloured light, known as auroras, in the polar night sky. Surges in electricity transmission lines can cause widespread power blackouts, as happened in Quebec, Canada, in March 1989 when 6 million people were left without electricity as a result of a huge solar-induced magnetic storm. Damage to microchips and electrical discharges can cause satellites to stop operating, disrupting telephone, TV and data communication services.
Radiation levels can become hazardous to astronauts and occupants of high-flying aircraft.
Variations in solar energy output cause global climate changes which affect plant growth, crop production and food supply.