Energy transfer from excited N 2 and O 2 as a source of O( 1S) in the Aurora

Abstract

It is proposed that energy transfer from excited O 2 contributes to the production of O( 1S) in aurora. An analysis is presented of the OI5577 Å emission in an IBC II + aurora between 90 and 130 km. The volume emission rate of the emission at these altitudes is consistent with the production rate of O( 1S) by energy transfer to O( 3P) from N 2 in the A 3 Σ 2 + state and O 2 in the A 3Σ u +, C 3 Δc 1 Σ u − states, the N 2 A state being populated by direct electron impact excitation and B → A cascade and the excited O 2 states by direct excitation. Above the peak emission altitude (~105 km), energy transfer from N 2 A is the predominant production mechanism for O( 1S). Below it, the contribution from quenching of the O 2 states becomes significant.