Response of the upper atmosphere to auroral protons

three-dimensional, time-dependent, coupled model of the thermosphere and io nosphere has been used to assess the influence of proton auroral precipitat ion on Earth's upper atmosphere. Statistical patterns of auroral electron a nd proton precipitation, derived from DMSP satellite observations, have bee n used to drive the model, Overall, electrons are the dominant particle ene rgy source, with protons contributing similar to 15% of the total energy. H owever, owing to the offset of the proton auroral oval toward dusk, in cert ain spatial regions protons can carry most of the energy. This is the case particularly at the equatorward edge of the dusk sector and at the poleward edge of the dawn sector of the auroral oval. The increase in Pedersen cond uctivity raises the average Joule heating by similar to 10%, so raising the E and F region temperature by as much as 7%. The enhanced E region ionizat ion also drives stronger neutral winds in the lower thermosphere through io n drag, which alters the temperature structure through transport, adiabatic heating, and adiabatic cooling. The neutral wind velocity modifications in the E region can reach 40% in some sectors. In addition, the upwelling of neutral gas raises the N-2/O ratio, depleting the F region and so reducing the ion-drag driven winds in this region. This study illustrates the modest yet significant impact of auroral proton precipitation on the upper atmosp here.