Auroras are caused by interactions between the solar wind and Earth's magnetic environment, which ultimately light up the upper atmosphere. Key points:

• The Sun emits a stream of charged particles (solar wind). When this wind intensifies or carries a southward magnetic field, it interacts more strongly with Earth’s magnetosphere [NOAA/NWS Space Weather Prediction Center describes this process].

• These interactions transfer energy into Earth’s magnetosphere, accelerating and directing charged particles (mainly electrons and protons) toward polar regions along magnetic field lines [Wikipedia overview of auroras].

• When these high-energy particles collide with atoms and molecules in the thermosphere/exosphere (mostly oxygen and nitrogen), they excite the atoms. As these excited atoms return to a lower energy state, they emit light, producing the visible curtains or arcs of the aurora.

• The color of the aurora depends on which atmospheric constituents are excited and at what altitudes:
  • Oxygen at higher altitudes (red and green hues) and nitrogen (purples, pinks, blues) contribute to the spectrum you see.

• Location and intensity:
  • Auroras occur most prominently near the magnetic poles because charged particles funnel along the polar field lines. Stronger solar activity produces brighter, more dynamic displays and can push auroral activity to lower latitudes.

• Triggers:
  • Solar events such as coronal mass ejections (CMEs) and solar flares inject large amounts of energetic particles into the solar wind, driving geomagnetic disturbances that create vivid auroras.

If you’d like, I can tailor this into a concise primer for beginners, or pull together a quick visual summary showing how solar wind, magnetosphere, and atmosphere interact to produce different aurora colors.