The Multiscale Dynamics of Lightning and a Moving Boundary Problem
Streamers pave the way of lightning strokes and of many other discharges in nature and technology. They are plasma fingers that penetrate non-ionized matter by a strong field enhancement at their tips. Each streamer has an intricate inner structure, and a discharge can form fractal-like trees with ten thousands of streamer branches. First I will review how far their very fast dynamics and multiscale structure are resolved by recent experiments and simulations. Then I will focus on derivation, tests and solutions of a moving boundary approximation for streamer fingers. The boundary approximation with “kinetic undercooling” regularization revives the question of the selection of Saffman-Taylor fingers and similar solutions. Quantitative predictions of the field enhancement at the streamer tips are important practical results.
Ute Ebert, Centrum voor Wiskunde en Informatica (CWI), The Netherlands