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

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 54 kV 28 kV A phase transition???

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

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

10. + - - - - + + + + + + + + + + - - - - - - - - - - - - + - - e—e— A A+A+ 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. Continuum approximation with Impact ionization e — + A  2 e — + A + Ohm’s law j ~ n e E Coulomb’s law n + — n e =  E

11. The multiscale challenge: 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)] z r electrons r z net charge

12. The multiscale challenge: 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] z r electrons r z net charge

13. The multiscale challenge: 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? z r electrons r z net charge

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