Self-consistent global transport of metallic ions with WACCM-X

Abstract

The NCAR Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCM-X) v2.1 has been extended to include the neutral and ion–molecule chemistry and dynamics of three metals (Mg, Na, and Fe), which are injected into the upper mesosphere–lower thermosphere by meteoric ablation. Here we focus on the self-consistent electrodynamical transport of metallic ions in both the E and F regions. The model with full ion transport significantly improves the simulation of global distribution and seasonal variations of Mg+, although the peak density is slightly lower (about 35 % lower in peak density) compared with the SCIAMACHY measurements. Near the magnetic equator, the diurnal variation in upward and downward transport of Mg+ is generally consistent with the “ionosphere fountain effect”. The thermospheric distribution of Fe is shown to be closely coupled to the transport of Fe+. The effect of ion mass on ion transport is also examined: the lighter ions (Mg+ and Na+) are transported above 150 km more easily than the heavy Fe+. We also examine the impact of the transport of major molecular ions, NO+ and O2+, on the distribution of metallic ions.