Transport of aurorally produced N(2D) by winds in the high latitude thermosphere

A time-dependent two-dimensional numerical model of the minor neutral constituents of the thermosphere NO, N(²D), and N(⁴S) is used to examine the effects of winds in transporting these constituents from their production region in auroral arcs. The calculations show that thermospheric winds flowing through regions of enhanced local auroral production produce downwind plumes of enhanced minor neutral constituent densities and that the densities depend upon the wind velocity. Below about 200 km N(²D) is in photochemical equilibrium and is not transported. Above 200 km N(²D) is transported by the wind and since quenching of N(²D) by O is small and the radiational lifetime is long, a downwind plume of emission at 5200 Å develops from the particle source region. We present data from a rocket flight in the vicinity of the magnetospheric cusp and data from the Atmosphere Explorer-D (AE-D) satellite that both show enhanced 5200 Å emission rates in a general downwind direction from a region of direct particle precipitation. The general wind speed and direction are obtained from predictions made by the NCAR thermospheric general circulation model. The results suggest that transport of N(²D) by the wind system is more important than the convection of O⁺ ions by electric fields in causing the enhanced 5200 Å emission rate in regions outside but in the vicinity of direct particle precipitation.