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Ann. Geophys., 26, 13-27, 2008
www.ann-geophys.net/26/13/2008/
© European Geosciences Union 2008
Parameterisation of the chemical effect of sprites in the middle atmosphere
C.-F. Enell1, E. Arnone2,*, T. Adachi3,**, O. Chanrion4, P. T. Verronen5, A. Seppälä5, T. Neubert4, T. Ulich1, E. Turunen1, Y. Takahashi3, and R.-R. Hsu6
1Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
2Dept. of Physics and Astronomy, Leicester University, UK
3Dept. of Geophysics, Tohoku University, Sendai, Japan
4Danish National Space Center, Technical University of Denmark, Copenhagen, Denmark
5Earth Observation unit, Finnish Meteorological Institute, Helsinki, Finland
6Dept. of Physics, National Cheng Kung University, Tainan, Taiwan
*now at: Dept. of Physical Chemistry, University of Bologna, Italy
**now at: Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan
Abstract. Transient luminous events, such as red sprites, occur in the middle
atmosphere in the electric field above thunderstorms. We here
address the question whether these processes may be a significant
source of odd nitrogen and affect ozone or other important trace
species. A well-established coupled ion-neutral chemical model has
been extended for this purpose and applied together with estimated
rates of ionisation, excitation and dissociation based on
spectroscopic ratios from ISUAL on FORMOSAT-2. This approach is used
to estimate the NOx and ozone changes for two type
cases.
The NOx enhancements are at most one order of magnitude in
the streamers, which means a production of at most 10 mol per
event, or (given a global rate of occurrence of three events per
minute) some 150–1500 kg per day. The present study
therefore indicates that sprites are insignificant as a global
source of NOx. Local effects on ozone are also negligible,
but the local enhancement of NOx may be significant, up to 5
times the minimum background at 70 km in extraordinary cases.
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