Energetic particle precipitation effects on the Southern Hemisphere

[1] Measurements from several different satellite instruments are used to estimate effects of energetic particle precipitation (EPP) on NOx (NO + NO2) in the Southern Hemisphere stratosphere from 1992 to 2005. The focus is the EPP Indirect Effect (IE), whereby NOx produced in the mesosphere or thermosphere via EPP (EPP-NOx) descends to the stratosphere during the polar winter, where it can participate in catalytic ozone destruction. EPP-NOx entering the stratosphere is found to vary in magnitude from 0.1 to 2.6 gigamoles per year, with maximum values occurring in 1994 and 2003. The interannual variation correlates strongly with several measures of EPP activity, including auroral and medium energy electron hemispheric power, and satellite measurements of thermospheric NO. This represents the first estimation of EPP-NOx contributions to the stratospheric odd nitrogen budget using observations over an entire solar cycle. The results will be useful for evaluating and constraining global models to investigate coupling of the upper and lower atmosphere by the EPP IE, including any influences this might have on ozone trends and possibly on climate