TIMED/SABER Observations of NO Radiance and Ozone Changes at High Latitudes

Saber (Sounding of the Atmosphere using Broadband Emission Radiometry experiment) data between 2002 and 2004) are used to investigate the response of the Earth's southern hemisphere (SH) atmosphere between 30 km and 160 km to possible Energetic Particle Precipitation (EPP) caused by solar activity. Nitric oxide (NO) radiance, treated as a proxy for NO mixing ratio, shows two peaks; one in the upper stratosphere at 45 km and the other in the lower thermosphere at 120 km. The peak values are relatively low when EPP is weak. When large EPP events occur, the upper level peak shows an immediate and strong increase, as does the lower level peak, most likely as a result of downward penetration. The upper level peak, however, decays within a very short time of only a few days, while the lower level peak has a more prolonged existence and at the same time descends to a layer 15-20 km lower in altitude in a time scale of three months or longer. It is worth pointing out that the NO radiance is also sensitive to the temperature. Therefore in the upper stratosphere the changes follow the seasonal warming or cooling but the component arising from EPP stands out from the background atmospheric change. SABER NO radiances and simultaneous ozone measurements suggest that winter time EPP events cause NO accumulation in the stratosphere leading to ozone destruction.