Polar lights

In short: Polar lights occur when charged particles from the Sun hit the Earth’s atmosphere and make gases glow. They are mostly seen near the polar circles.

In more detail: The solar wind is steered by the Earth’s magnetic field to the poles. At around 100 kilometres altitude the particles excite oxygen and nitrogen.

In detail

• Colours: Green arises from oxygen at low altitude, red from oxygen at great height, violet and blue from nitrogen.
• Northern and southern lights: Aurora borealis in the north, aurora australis in the south.
• When: In clear, dark skies, especially in long winter nights and during strong solar activity (solar storms, about 11-year cycle).
• In Germany: Visible in the north during very strong solar storms.
• Magnetic field: Without the magnetismus-grundlagen of the Earth’s core the solar wind would strip away the atmosphere.