Summary

In the past decade, several types of optical emissions occurring above thunderstorms have been identified. The emissions span the middle- and upper-atmosphere between thunderstorm tops and ~95 km. Spectroscopic and filtered observations of sprites and blue jets have been presented and discussed. The observed nitrogen emissions indicate electrons with energies of at least 18.6 eV are required to describe some of the observed emissions. A 1 eV Boltzmann electron distribution (modified with a high energy tail component) matches the observations and is physically realistic. Based on observations of the total optical energy emitted by a sprite, we estimate the total energy depositied into active molecular nitrogen (both vibrational and electronic state energy) to range from 250 MJ to 1 GJ. Recent observations from EXL98 under current analysis will help clarify and confirm these values. The preliminary estimate on global occurrence rates of sprites, blue jets, and elves, is on the order of 1 per second.

Acknowledgments

Dan Osborne, Jim Desroschers, Laura Peticolas, Veronika Besser, and Don Hampton were instrumental to assisted with data collection and campaign operations. We also thank the High-frequency Active Auroral Research Program for loan of the Near-IR instruments used in the aircraft missions. Aeroair, Inc. and particularly Jeff Tobolsky made all UAF aircraft missions fly. MJH acknowledges Dirk Lummerzheim for fruitful discussion. The GI-UAF, NRL, and Raytheon groups were supported by NASA Grant No. NAG5-5019. JSM was partially supported by the Edison Memorial graduate training program at NRL, EJB was supported by ASEE postdoc funding, and CLS was supported by ONR 6.1 money.