CEDAR: Atmospheric Coupling via Energetic Electron Precipitation (EEP)

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

The award would study the downward transport from the mesosphere and lower thermosphere (MLT) of reactive nitrogen species (NOx) that are generated within the Arctic. The award would concentrate upon the study of an event that happened in the Arctic spring of 2004 for which an enormous influx of NOx from the mesosphere and lower thermosphere (MLT) was observed to enter the polar stratosphere, thus increasing the NOx mixing ratios in the upper stratosphere by a factor of 4. This action in turn caused for those altitudes localized catalytic reductions in ozone of more than 60%. The processes leading to this influx, which were initiated by energetic electron precipitation (EEP), occur routinely and they have not yet been satisfactorily modeled. The proposed work would improve the understanding of EEP effects on the atmosphere in general, and the coupling between the MLT and the lower atmosphere in particular. A comprehensive description of Sun-Earth connections requires the quantification of the atmospheric processes that indirectly amplify the effects of solar and magnetospheric input. This includes nonlinear feedbacks between chemical, radiative, and dynamical processes that couple different regions of the atmosphere. The atmospheric response to EEP is a key component of Sun-Earth connections and provides a natural means of probing the underlying physics. This award would address an obvious deficiency with regard to the explanation and prediction of the effects of EEP on the atmosphere. The Whole Atmosphere Community Climate Model (WACCM) developed by the National Center of Atmospheric Research would be used in conjunction with observations from numerous instruments to answer four primary questions: 1) Why does WACCM underestimate the amount of reactive odd nitrogen (NOx) that descended from the MLT during the Arctic winter of 2003-2004; 2)How well does it perform during other Arctic and Antarctic winters? 3), Given the extreme variability in the polar region, what statistical data sets are optimal for examining the atmospheric coupling processes that are relevant to EEP? and 4) What are the atmospheric effects of EEP after auroral electron precipitation and after higher energy electron precipitation?