Aurora borealis is caused by charged particles from the Sun interacting with Earth’s atmosphere, guided by the planet’s magnetic field, and lighting up atoms in the upper atmosphere. What happens in brief
- The Sun emits a stream of charged particles (the solar wind), sometimes in bursts during solar storms.
- When these particles reach Earth, they interact with the magnetosphere and are channeled toward the polar regions by Earth’s magnetic field.
- As they collide with gas molecules (mainly oxygen and nitrogen) high in the atmosphere, the gas atoms get excited and then release light as they return to their normal energy states. This light forms the shimmering curtains, rays, and bands we see as the aurora.
Key details
- Colors come from different gases and altitudes:
- Green (the most common color) mostly arises from oxygen at altitudes around 100–300 km.
- Red, purple, and blue hues come from higher-altitude oxygen and from nitrogen interactions, with intensity and color mix depending on energy input and altitude.
- Typical altitude range:
- Visible auroras generally occur between about 80 km and a few hundred kilometers above the Earth, with some emissions extending higher during intense events.
- Location and timing:
- Auroras are most vivid and frequent near the magnetic poles, but strong solar activity can extend sightings to lower latitudes and broader areas.
How solar activity shapes it
- When solar wind speed increases or the interplanetary magnetic field turns southward, geomagnetic activity intensifies, making auroras brighter and more widespread.
- Even moderate solar wind can produce faint auroras at high latitudes; powerful storms can produce spectacular displays seen far from the poles.
If you’d like, I can tailor this explanation to a specific audience (kids, students, hikers) or add a simple diagram description to help visualize the process.