streamers, sprites, leaders, lightning: from micro- to macroscales workshop, oct. 8-12, 2007,...
DESCRIPTION
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, lightningTRANSCRIPT
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)
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!
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, solidsDependence on electric circuit (voltage, polarity, …) and on
magnetic fieldStreamer ignition, streamer to leader transition
Leaders, lightning
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!
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 kV4 cm
300 ns
Streamer discharge in ambient air (TUE):
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?
Air, 40 mm,
exposure 2 ns54 kV 28 kV
A phase transition???
Air, 40 mm,
exposure 50 ns54 kV 28 kV
A phase transition???No, continuous.[T. Briels et al., J. Phys. D 39, 5201 (2006)]
Experiments show many unexpected features,
also when changing polarity and gas composition.
Theory???
54 kV 28 kV
+
- - - -+
++
+++++
+
+-
--
---
-
--
--
-+-
-
e—
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 withImpact ionization e— + A 2 e— + A+
Ohm’s law j ~ ne ECoulomb’s law n+— n e = E
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
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
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
Streamers, sprites, leaders, lightning:from micro- to macroscales
Let’s try to make progress this week!