Characterization and model comparison of positive leaders in rocket-triggered lightning.

摘要

Records of the surface electric field near, and current within, grounded wires pulled aloft by rockets to trigger lightning flashes show at low wire heights (102--213 m) initially intermittent pulses later followed at higher wire heights (230--447 m) by continuous features respectively identified as arrested and ultimately successful discharges from the wire tip. Analysis of pulse charge, timing, rocket velocity, and wire height, together with information about the electric field and potential profiles the wires were injected into [Willett et al., Atm.Res.1999] permits characterization of discharge length, line charge density, velocity, and energy. Three models are compared, the first two [Lalande et al 1997b, Bazelyan and Raizer 2000] originating from laboratory discharges, the third resulting from equating an empirically determined requisite formative energy with that electrostatically available under idealization of the discharge as an expanding ellipsoid. All models performed comparably, there being no statistically significant difference between them. The comparability of model performance, together with the similitude of parameters to those of laboratory discharges, confirms the identity of the discharges as 'streamer-leader systems' [asserted by Lalande et al. 1998 p.14113] and extends applicability of long laboratory spark results to lightning scales. The semi-empirical model developed further provides a useful tool for aerospace and lightning protection applications with simple energetic criteria for arrest or viability.