The Influence of Energetic Electron Precipitation on the Atmosphere
Cora E. Randall [Cora.Randall@lasp.colorado.edu], Laboratory for Atmospheric and
Space Physics, University of Colorado, Boulder
Research into the effects of energetic particle precipitation (EPP) on the atmosphere has
expanded significantly in recent years. EPP leads to the production of odd nitrogen (NOy) and
odd hydrogen (HOx), both of which participate in catalytic ozone chemistry. This talk focuses
on the longer lived NOy. Solar protons and very high energy electrons can produce NOy directly
in the stratosphere, where most of the ozone resides. Lower energy electrons such as those that
precipitate into the auroral region will produce NOy in the lower thermosphere. During the polar
winter this NOy can descend into the stratosphere. This talk will describe recent simulations with
the NCAR Whole Atmosphere Community Climate Model (WACCM) of the atmospheric
effects of precipitating auroral electrons. The model shows the largest effects in the southern
hemisphere, with significant ozone depletion in the polar middle stratosphere during the late
winter, spring, and summer. In addition, the model predicts that the excess NOy will interfere
with the ozone "hole" chemistry, tying up ClO and thus reducing the total amount of ozone loss
in the lower stratosphere. It is also found that the change in ozone so induced leads to changes in
latitudinal gradients in temperature that cause changes in zonal winds and wave filtering in the
polar summer, leading to changes in the mesospheric residual circulation.