Northern lights (aurora borealis) happen when charged particles from the Sun collide with atoms in Earth's atmosphere, causing those atoms to emit light that we see as glowing curtains or waves near the polar regions. The process is guided by Earth's magnetic field, which funnels most of the solar particles toward the polar regions. Key points

• Source of the particles: The Sun ejects streams of charged particles, especially during solar wind, solar flares, and coronal mass ejections. These particles travel through space and can reach Earth.

• Interaction and light: When these energetic particles hit atoms and molecules in the upper atmosphere (primarily oxygen and nitrogen), they excite those atoms. As the excited atoms return to their ground state, they emit photons, producing visible light in various colors. The different colors arise from the specific atoms and the altitude of the emissions.

• Why near the poles: Earth’s magnetic field guides many of the incoming particles toward the magnetic poles, creating the characteristic auroral ovals over northern and southern latitudes.

• Colors and altitude: Common colors include green (from excited oxygen around 100–300 km up) and red or purple hues from higher or different atomic transitions. The altitude and particle energy influence the exact colors seen.

• Activity varies with solar cycles: Auroral activity tends to increase during periods of heightened solar activity (near sunspot maxima), which can make auroras visible at lower latitudes and more intense.

Additional context

• Visibility: The phenomena are more readily visible on clear, dark nights away from city lights, and are often predicted using space weather alerts that track solar activity and magnetospheric conditions.

• Historical and ongoing understanding: The basic mechanism has been understood for decades, with modern models linking solar wind, the magnetosphere, and atmospheric collisions to auroral displays.

Direct answer: The Northern Lights occur because the Sun constantly releases charged particles that travel to Earth. When these particles collide with atmospheric atoms (mainly oxygen and nitrogen) high in the atmosphere, they transfer energy and emit light. Earth's magnetic field directs many of these particles toward the polar regions, creating the visible auroral curtains near the North Pole (and the South Pole). The exact colors depend on the types of atoms involved and the altitude of the collisions, with green and red being common due to oxygen and purple/blue tones from other transitions. Activity intensifies with stronger solar activity, which can make auroras brighter and sometimes visible farther from the poles.