Characterization of N⁺ Abundances in the Terrestrial Polar Wind Using the Multiscale Atmosphere-Geospace Environment

The High-latitude Ionosphere Dynamics for Research Applications (HIDRA) model is part of the Multiscale Atmosphere-Geospace Environment model under development by the Center for Geospace Storms NASA DRIVE Science Center. This study employs HIDRA to simulate upflows of H⁺, He⁺, O⁺, and N⁺ ions, with a particular focus on the relative N⁺ concentrations, production and loss mechanisms, and thermal upflow drivers as functions of season, solar activity, and magnetospheric convection. The simulation results demonstrate that N⁺ densities typically exceed He⁺ densities, N⁺ densities are typically ∼10% O⁺ densities, and N⁺ concentrations at quiet-time are approximately 50%–100% of N⁺ concentrations during storm-time. Furthermore, the N⁺ and O⁺ upflow fluxes show similar trends with variations in magnetospheric driving. The inclusion of ion-neutral chemical reactions involving metastable atoms is shown to have significant effects on N⁺ production rates. With this metastable chemistry included, the simulated ion density profiles compare favorably with satellite measurements from Atmosphere Explorer C and Orbiting Geophysical Observatory 6.