A two-dimensional model of thermospheric nitric oxide sources and their contributions to the middle atmospheric chemical balance

The NASA/Goddard Space Flight Center two-dimensional (GSFC 2D) photochemica l transport model has been used to study the influence of thermospheric NO on the chemical balance of the middle atmosphere. Lower thermospheric NO so urces are included in the GSFC 2D model in addition to the sources that are relevant to the stratosphere. A time series of hemispheric auroral electro n power has been used to modulate the auroral NO production in the auroral zone. A time series of the Ottawa 10.7-cm solar flux index has been used as a proxy to modulate NO production at middle and low latitudes by solar EUV and soft X-rays. An interhemispheric asymmetry is calculated for the amoun ts of odd nitrogen in the polar stratosphere. We compute a <similar to 3% e nhancement in the odd nitrogen (NOy = N, NO, NO2, NO3, N2O5, BrONO2, ClONO2 , HO2NO2 and HNO3) budget in the north polar stratosphere (latitude > 50 de grees) due to thermospheric sources, whereas we compute a < similar to 8% e nhancement in the NOy budget in the south polar stratosphere (latitude > 50 degrees). (C) 2000 Elsevier Science Ltd. All rights reserved.