Articles | Volume 26, issue 1
Ann. Geophys., 26, 13–27, 2008
Ann. Geophys., 26, 13–27, 2008

  04 Feb 2008

04 Feb 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 C.-F. Enell et al.
  • 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.