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DY: Fachverband Dynamik und Statistische Physik

DY 6: Quantum Dynamics, Decoherence, and Quantum Information I

DY 6.10: Hauptvortrag

Montag, 14. März 2011, 16:30–17:00, ZEU 255

The multiscale dynamics of lightning and of terrestrial gamma-ray flashes — •Ute Ebert — CWI Amsterdam, The Netherlands — Eindhoven Univ. Techn., The Netherlands

Today most research on cloud-to-ground lightning concentrates on lightning protection. But reserach on lightning physics received a new boost through the discovery of transient luminous events above active thunderstorms in 1990 and of terrestrial gamma-ray flashes from thunderstorms in 1994. In particular, sprite discharges that develop at 40 to 90 km altitude are the first lightning phenomena whose dynamics we now start to understand quantitatively. Sprites are up-scaled versions of streamer discharges, that play an important role in lightning, sparks and high voltage technology.

I will discuss how to bridge the 10 orders of magnitude between the underlying electron-molecule collisions and the km long lightning strokes. I will sketch the hierarchy of dynamical phenomena, and I will focus on: 1. the nonlinear dynamics of sprite and streamer discharges. They are modeled by reaction-drift-diffusion equations and form finger-like structures, that are similar to fingers in two-fluid-flow, in dendritic solidification fronts etc. 2. the single electron dynamics within the streamer. If the field at the finger tip is sufficiently enhanced, the electron density approximation breaks down locally, and electrons run away. This is a possible cause of terrestrial gamma-ray flashes.

Find more information on http://homepages.cwi.nl/~ebert.