Articles | Volume 26, issue 1
04 Feb 2008
 | 04 Feb 2008

Parameterisation of the chemical effect of sprites in the middle atmosphere

C.-F. Enell, E. Arnone, T. Adachi, O. Chanrion, P. T. Verronen, A. Seppälä, T. Neubert, T. Ulich, E. Turunen, Y. Takahashi, and R.-R. Hsu

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.