Streamers, sprites, leaders, lightning: from micro- to macroscales

1. Streamers, sprites, leaders, lightning: from micro- to macroscales Workshop, Oct. 8-12, 2007, Lorentz Centre Organizers: Ute Ebert (CWI Amsterdam, TU Eindhoven), Davis D. Sentman (Fairbanks, Alaska)

2. Many disciplines: • Applied math, computational science, theoretical physics, • applied physics, electrical engineering, industry, • geophysics on atmospheric electricity: • lightning, transient luminous events, terrestrial gamma ray flashes  Avoid terminology slang • that other disciplines might not be familiar with!

3. Many disciplines – but common subjects: Streamer-like discharges in various media: Air at a large range of pressures, argon, nitrogen, air-fuel-mixtures, combustion gases, supercritical fluids, liquids, solids Dependence on electric circuit (voltage, polarity, …) and on magnetic field Streamer ignition, streamer to leader transition Leaders, lightning

4. Many disciplines – but common subjects: Complex subject: very many scales in space and time, from microscopic cross sections up to macroscopic streamers. Input: electric power into a given medium, Output: distribution of conductivity, chemical excitations, X-rays Major challenge for observations and modeling!  Join forces!

5. Streamer discharge in ambient air (TUE): +28 kV 4 cm 300 ns Why? Basic physical interest in start up of sparking ● Spark plug in car engine ●Ozone generation for disinfection ●Start of energy saving lamps ●Lightning …

6. 4 cm Telescopic images of sprite discharges [Gerken et al., Geophys. Res. Lett. 2000] 4 cm Similarity law: 1 bar versus 10-5 bar … even 30 bar in lamps and spark plugs! What can we learn from each other?

7. Air, 40 mm, exposure 2 ns A phase transition??? 54 kV 28 kV

8. Air, 40 mm, exposure 50 ns A phase transition??? No, continuous. [T. Briels et al., J. Phys. D 39, 5201 (2006)] 54 kV 28 kV

9. Experiments show many unexpected features, also when changing polarity and gas composition. Theory??? 54 kV 28 kV

10. e— Fast processes in the ionization front: 10-9 m: 10-6 m: + + + + + + Electrons drift and diffuse in local E-field. Elastic, inelastic and ionizing collisions with neutral molecules. Degree of ionization < 10-4. - - - - - + - - + + - E - + A+ + - + - + A - Continuum approximation with Impact ionizatione—+ A  2 e—+ A+ Ohm’s lawj ~ neE Coulomb’s lawn+— n e= E - + - + - - - + + - + — — — — — —

11. Solve Poisson equation everywhere. Solve densities in ionized region. Resolve steep density gradients with high accuracy. • Do not exceed computational memory. [U. Ebert et al., Plasma Sources Sci. Technol. 15, S118 (2006)] [C. Montijn et al., Phys. Rev. E 73, 065401 (2006)] [C. Montijn et al., J. Comput. Phys. 219, 801 (2006)] [A. Luque et al., Appl. Phys. Lett. 90, 081501 (2007)] electrons net charge z z r r The multiscale challenge:

12. Solve Poisson equation everywhere. Solve densities in ionized region. Resolve steep density gradients with high accuracy. • Do not exceed computational memory. 3D, interacting streamers: [A. Luque et al., proceedings ICPIG 2007 and in preparation] electrons net charge z z r r The multiscale challenge:

13. Solve Poisson equation everywhere. Solve densities in ionized region. Resolve steep density gradients with high accuracy. Take particle nature into account locally! [C. Li et al., J. Appl. Phys. 101, 123305 (2007) and submitted]  Explain chemical processes and X-ray emission from lightning? electrons net charge z z r r The multiscale challenge:

14. Streamers, sprites, leaders, lightning: from micro- to macroscales Let’s try to make progress this week!