MEDIUM-ENERGY PARTICLE-PRECIPITATION INFLUENCES ON THE MESOSPHERE ANDLOWER THERMOSPHERE

Data accumulated for more than a solar cycle by the TIROS/NOAA polar o rbiting satellites are used to extract patterns of particle precipitat ion in several medium energy bands for varying geomagnetic conditions. While the atmospheric effects of amoral particles measured by these s atellites (300 eV-20 keV) have been widely studied, the effects of med ium energy (30 keV-2.5 MeV) particles have received less attention; in this paper we present average particle precipitation patterns for med ium energy protons and electrons as a function of geomagnetic activity . A magnetic coordinate system is used to bin data at high latitudes t o produce patterns that are then used as additional inputs to the Nati onal Center for Atmospheric Research thermosphere ionosphere mesospher e electrodynamic general circulation model (TIME-GCM) to study the eff ects of medium energy particles on the mesosphere and lower thermosphe re. Model results obtained with these additional inputs are used to as sess the significance of medium energy particles on the composition an d dynamics of the region. Zonally averaged model results from the run that includes the medium energy particles show significant increases i n, n(e), HOX, NO2, and NO and a 27 percent decrease in O-3 between 70 and 80 km in the polar regions when compared to a similar run without the particles. The temperature and wind differences are small.