A Time-Dependent Model of the Vibrational Distribution of Nitrogen Molecules: New Rate Data Sets and Self-Consistent Coupling With Auroral and Ionospheric Electrons

Abstract

Vibrationally excited nitrogen molecules (N₂) play an important role in the chemistry and dynamics of Earth's atmosphere. Electron impact, whether it originates from auroral precipitation or ionospheric thermal electrons, is among the major causes of the vibrational excitation of N₂. Due to the co-existence of excitation and deexcitation, the net energy exchange between electrons and N₂ molecules depends on the N₂ vibrational distribution, so that the electron energy distribution and the N₂ vibrational distribution are inherently coupled. In this study, we introduce a new model to simulate the time-dependent vibrational distribution of N₂, incorporating self-consistent ionospheric dynamics and mutual energy exchange with auroral suprathermal electrons and ionospheric thermal electrons. We demonstrate that the model runs under strong auroral precipitation and strong heating conditions within the framework of our previously established Transition Region Explorer Auroral Transport Model (TREx-ATM). We elucidate the time-varying characteristics of the N₂ vibrational state densities, their altitude profiles and major contributing mechanisms, as well as the dynamic coupling among the N₂ vibrational distribution, the auroral suprathermal electrons, and the ionospheric thermal electrons. A few notable effects of the intensified N₂ vibrational excitation on the ionospheric and thermospheric chemistry are addressed. Our model may help advance the understanding of the role and dynamics of vibrationally excited N₂ in cross-regional coupling under disturbed times.