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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,

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Presentation Transcript
slide1

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)

slide2

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!
slide3

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

slide4

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!

slide5

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

slide6

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?

slide7

Air,

40 mm,

exposure

2 ns

A phase transition???

54 kV 28 kV

slide8

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

slide9

Experiments show many unexpected features,

also when changing polarity and gas composition.

Theory???

54 kV 28 kV

slide10

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

-

+

-

+

-

-

-

+

+

-

+

— — — — — —

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)]

electrons

net charge

z

z

r

r

The multiscale challenge:
the multiscale challenge1

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:
the multiscale challenge2

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:
slide14

Streamers, sprites, leaders, lightning:

from micro- to macroscales

Let’s try to make progress this week!