Altitude of Emission: Red auroras typically occur at higher altitudes, around 180 to 250 miles (300 to 400 km), where the density of atmospheric gases is lower.
At these altitudes, the collisions between solar particles and oxygen atoms are less frequent, allowing the excited oxygen atoms to emit red light (wavelength of 630.0 nm) with a mean lifetime of about 100 seconds.
However, because the emissions are less frequent and occur in a less dense medium, the overall display can appear shorter-lived compared to more abundant emissions at lower altitudes.
Energy of Precipitating Particles: The energy of the auroral electrons plays a crucial role in determining the altitude at which they can excite atmospheric gases
Higher-energy particles can penetrate deeper into the atmosphere, leading to green emissions at lower altitudes (around 60 to 190 miles or 100 to 300 km) where oxygen is more concentrated.
Movement and Structure: The long lifetime of red emissions allows for the aurora to move and change shape before the light is emitted.
This can cause the detailed structure of the auroral display to be less distinct, making red auroras appear less vibrant and shorter-lived compared to the more dynamic green auroras