MHD Jets in the Laboratory

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MHD Jets in the Laboratory
Andrea Ciardi Observatoire de Paris (LUTH)
S. V. Lebedev, J. P. Chittenden S. N. Bland, S.
C. Bott, J. Rapley, G. N. Hall, F. A. Suzuki
Vidal, A. Marocchino Imperial College
A. Frank, E. G. Blackman University of Rochester
T. Lery DIAS
C. Stehle Observatoire de Paris
D.J. Ampleford, C.A. Jennings Sandia National
Laboratories
The present work was supported in part by the
European Communitys Marie Curie Actions Human
Resource and Mobility within the JETSET (Jet
Simulations Experiments and Theory) network under
contract MRTN-CT-2004 005592.
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What is in the jet formation?
Jet
Poorly collimated flow
Ambient Medium
Magnetic Fields
Outflow Region
Disc
Rotation
Driving Region
Compact Object (Gravity)
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Simplifying the jet formation
Twisting of the field, results into
Jet
Ambient Medium
Magnetic Fields
Outflow Region
Driving Region
Is the interaction of a purely toroidal field
with an ambient medium enough to reproduce some
of the complex behaviour seen in space? or even a
jet?
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Making Magnetic Towers in the Laboratory
16 W wires ?13 µm 4 mm diameter inner
electrode 70 mm diameter outer electrode Peak
current 1 MA Rise time 240 ns
Jet
Magnetic Bubble
Environment
Ciardi et al (2005) Lebedev et al (2005)
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Simulations and Experiments
GORGON 3D resistive MHD
MAGPIE 3D resistive MHD (and more)
Single Fluid, Two Temperatures Optically-thin
radiation losses Thermal Conduction Computational
vacuum Parallel version ( 2000 processor hours)
Peak current 1 MA Rise time 240 ns
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Dynamics
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Dynamics 2
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Dynamics 3
Magnetic Cavity
Shock Envelope
288 ns
298 ns
268 ns
278 ns
time resolved XUV images (background emission
removed)
Magnetically confined Jet
azimuthally averaged
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A discrete world
- Azimuthal modulation in the background plasma
is not critical to the development of the
magnetic tower smoother for larger number of
wires - Magnetic cavity expands with a high
symmetry current is uniformly distributed
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A simple tower
Return current within 1 mm radius 90 of total
(210 ns)

Magnetic energy
Axial Expansion velocity
Because total current is approximately constant
(Zt depends on the background density and
velocity profile)
Transition in the evolution of the Magnetic
Tower Instabilities break-up the
jet Re-arrangement of magnetic field and currents
Large amplitude kink appears
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Break up and Ejection
Magnetic twist angle
simulated emission images
230 ns
240 ns
210 ns
220 ns
sausage
kink
Time
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The Emerging Jet
Highly Collimated Clumpy jet Radiatively
Cooled Super-fast-magnetosonic Blobs of plasma
in the jet ß 1- 5 Entrained Magnetic field
JET
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Summary
Laboratory magnetic jets show a complex
evolution Formation of jet and magnetic cavity.
Development of instabilities and break-up of the
tower. Launching of a jet.
Experiments
Simulations
There is one more step in the evolution Formatio
n of a new cavity and jet
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Adding more.
Rotation
Poloidal Field
coil ? 21 mm, placed 11 mm below the wires, 4
windings with 0.2 turns/cm hollow inner electrode
? 63 mm
280 ns