Polarlichter

Polarlichter, in English known as the aurora borealis in the northern hemisphere and the aurora australis in the southern hemisphere, are natural light displays in Earth's polar skies. They occur in high-latitude regions around the Arctic and, in the southern hemisphere, around Antarctica. The phenomenon results when charged particles carried by the solar wind enter Earth's magnetosphere and collide with atmospheric gas molecules. The subsequent excitation and relaxation of these atoms emit light that creates luminous curtains, arcs and bands.

The colors of the aurora depend on the gases involved and the altitude of the interaction. Green, the most common hue, comes from oxygen emissions at about 100 to 300 kilometers above the surface. Red auroras can appear at higher altitudes from oxygen, while blue and purple tones arise from nitrogen molecules. The shapes vary from diffuse glows to sharp arcs, rays or curtains that sway and ripple with the motion of the magnetospheric field. Auroras are dynamic and can change rapidly, sometimes producing pulsations or pulsating textures.

Occurrence and observation are governed by geomagnetic activity driven by the solar wind and solar flares. They are more frequent and intense during periods of strong solar activity and can shift toward lower latitudes during geomagnetic storms. Clear, dark skies and minimal light pollution are essential for viewing, with longer winter nights in polar regions offering better opportunities. Predictions rely on space-weather monitoring and auroral oval models.

Geography and history: In the north, polarlichter are commonly seen in Norway, Sweden, Finland, Iceland, Canada, Alaska, and Greenland. In the south, the aurora australis is visible from high southern latitudes, including parts of Antarctica and occasionally southern Chile, Argentina, New Zealand, and subantarctic islands. The phenomenon has long been observed and studied as part of space weather and upper-atmosphere physics.