抄録
Numerical simulations have been performed to investigate global changes of the neutral gas dynamics and composition in response to high-latitude energy input. Four simulations have been performed, at equinox, using a two-dimensional, time-dependent model of coupled dynamics and composition for modeled storms with various durations ranging from 3 hours to 24 hours. In order to study the dominant mechanisms responsible for the composition changes, a term analysis of the neutral composition equations has been performed. The major results are as follows; (1) the boundary between the regions of upwelling and of downwelling lies at 54° latitude for the storm heating longer than 9 hours, and 49° latitude for the 3 hours heating; (2) the boundary between the regions of positive change in mean molecular mass (m0) and negative one lies at49° latitude for the 3 hours heating, but it reaches 38° latitude for the 24 hours heating; (3) the boundary in Amo is located equatorward of the corresponding boundary between upwelling and downwelling, which means the penetration of the region of positive Δm0 into the region of the downwelling; (4) the degree of penetration largely depends on the duration of storm heating; (5) the primary cause of the composition changes for the storm heating longer than 9 hours is by horizontal and vertical advection associated with a storm circulation; for the 3 hour storm vertical advection from atmospheric gravity waves is the primary cause of the composition changes.
