What physical requirement must an oxygen atom meet at higher altitudes to produce the red auroral color?

Answer

It must remain in its excited state for a relatively long time (about 100 milliseconds)

For oxygen to emit red light, the atom needs a relatively quiet transition window, requiring it to remain excited for about 100 milliseconds before emitting a photon, rather than losing energy through collisional heat.

What physical requirement must an oxygen atom meet at higher altitudes to produce the red auroral color?

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