Ultraviolet (UV) radiation does not directly cause the aurora borealis, but it plays an important observational role in understanding this natural phenomenon.
Here’s how the aurora forms:
- Solar wind, composed of high-energy charged particles (mainly electrons and protons), streams from the Sun.
- When these particles reach Earth, they are guided by Earth’s magnetic field toward the polar regions.
- These charged particles collide with atoms and molecules in Earth’s upper atmosphere (mostly oxygen and nitrogen).
- These collisions excite the atmospheric atoms, causing them to emit light as they return to their normal state—this light is the aurora.
Role of UV Radiation:
While the aurora is mostly seen as visible light (green, red, purple), the excited atmospheric gases also emit ultraviolet radiation, which:
- Cannot be seen by the human eye, but can be detected by instruments and satellites.
- Helps scientists study auroral activity from space using UV cameras and sensors.
- Reveals auroral events on the day side of Earth, where visible auroras are washed out by sunlight.