HR: 11:35h
AN: SA42A-06 INVITED     [Abstracts]
TI: Impacts of Solar Superstorms on the Earth's Middle Atmosphere
AU: * Randall, C
EM: randall@lasp.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado UCB 392, Boulder, CO 80309 United States
AB: This presentation focuses on the effects of solar superstorms on the middle atmosphere, with an emphasis on the penetration depth and duration of these effects. The primary mechanism by which extreme solar events affect the middle atmosphere is via production of nitrogen oxides (NOx) after energetic particle impacts on molecular nitrogen and oxygen. The NOx catalytic cycle is the primary loss mechanism for ozone in the middle stratosphere, so solar storm effects that penetrate into the stratosphere play a critical role in controlling ozone distributions. Highly energetic solar protons can result in immediate NOx enhancements directly in the stratosphere, although this happens only rarely. More frequently, energetic protons and electrons lead to delayed enhancements of stratospheric NOx. That is, production of NOx first occurs in the mesosphere and thermosphere; under appropriate conditions, the NOx so produced will then descend into the stratosphere. The current status of our understanding of this type of coupling between solar storms and stratospheric composition will be reviewed. Evidence will be presented for both immediate and delayed enhancements of NOx in the stratosphere following the solar storms of October 2003. Stratospheric NOx enhancements in the northern hemisphere springtime of 2004 were unprecedented in the available satellite data sets going back to 1979, and persisted into the summer. These NOx enhancements were accompanied by unprecedented reductions in ozone. The observations of 2003-2004 will be compared to those in other years where more subtle, but often analogous, effects pertained. Areas of largest uncertainty in our understanding of the coupling between superstorms and lower altitudes will be highlighted, and needs for future measurements and modeling will be discussed.
DE: 2716 Energetic particles, precipitating
DE: 2788 Storms and substorms
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting