what makes the northern lights red

The red color in the Northern Lights (aurora borealis) comes from excited oxygen atoms at higher altitudes in Earth's atmosphere. When high-energy solar particles collide with oxygen far above the surface, the oxygen emits light at red wavelengths, producing red or crimson hues that are often seen near the edges or higher portions of the aurora. Red auroras typically occur at altitudes around 300–400 km (about 190–250 miles) or higher, where the oxygen density is lower and the excited-state transitions favor red emission. This phenomenon can appear alongside the more common green auroras, which arise from oxygen emissions at lower altitudes, and it is more likely to be visible during periods of strong solar activity when energetic particles reach higher altitudes.