Blue-light imagery and photometry of sprites

We have obtained blue (350-475 nm) video images and simultaneous high-time resolution narrow-band blue (415-435 nm) photometry records of four sprite events. The brightest blue images show a sustained tendril geometry and a nearly constant intensity of emission over the entire vertical extent of the sprite (from 35-90 km altitude). Photometer light curves display an exponential decay with a 0.3 ms time constant, a FWHM on the order of 0.1-1.0 ms, and are probably dominated by 427.8 nm (N-2(+) 1N) emission. The data support the observations of Armstrong et al. (1998) and support the contention that significant ionization occurs during sprite generation. (C) 1998 Elsevier Science Ltd. All rights reserved.