Auroras are caused by interactions between energetic particles from the Sun and the Earth’s magnetic environment, which energize and excite atoms in the upper atmosphere to emit light. Key points

• Solar wind and solar storms: Streams of charged particles (electrons and protons) emitted by the Sun travel toward Earth. When these particles reach Earth, they interact with the planet’s magnetic field and magnetosphere. The intensity and timing of auroral displays are tied to solar wind conditions and events like coronal mass ejections, which inject more energy into the system. [noaa web]
• Magnetospheric interaction: The solar wind disturbs Earth’s magnetosphere, creating electric fields and wave activity. These disturbances accelerate and guide charged particles along magnetic field lines toward the polar regions. This acceleration increases particle energies and the likelihood of precipitation into the upper atmosphere.

• Atmospheric illumination: Once the energized particles collide with atmospheric gases (primarily oxygen and nitrogen) at altitudes from about 80 to several hundred kilometers, they excite those atoms and molecules. When these excited states return to lower energy levels, they emit light in various colors, producing the visible aurora. The color depends on the gas and the energy of the collision (e.g., green from oxygen at lower altitudes, red and purples from higher altitudes, and purples/blue from nitrogen).

• Geographic distribution and shapes: Auroras occur most strongly near the magnetic poles because intense particle precipitation follows magnetic field lines toward high-latitude regions. The shimmering curtains, arcs, and rays arise from the 3D structure of the magnetic field and the wave-particle interactions in the magnetosphere.

• Variability: The display’s brightness and extent respond to solar wind speed, density, and the direction of the interplanetary magnetic field (IMF). A southward IMF often enhances coupling to Earth’s field, boosting auroral activity and moving the glow equatorward.

If you’d like, I can summarize this with a quick diagram-like explanation or point to specific resources for more in-depth physics.