STM-D-0966Paper2009Published and peer-reviewed

Formation of episodic magnetically driven radiatively cooled plasma jets in the laboratory

F. Suzuki-Vidal · S. V. Lebedev · A. Ciardi · S. N. Bland · J. P. Chittenden · G. N. Hall · A. J. Harvey-Thompson · A. Marocchino · Cheng Ning · C. Stehlé · Adam Frank · Eric G. Blackman · S. C. Bott · T. P. Ray

Abstract and summary · read the original at the source

In one page

Astronomers see jets from young stars that arrive in bursts — knots and shocks strung along the flow, as though the engine switched on and off. Francisco Suzuki-Vidal, Sergey Lebedev and colleagues at Imperial College, with collaborators in Paris, Rochester, San Diego and Dublin, made one in a laboratory. On the MAGPIE machine a million amps rises in 250 billionths of a second through a thin aluminium foil; the toroidal magnetic field underneath lifts a magnetic bubble and pinches a jet along its axis — the magnetic tower that theorists propose for the real thing. The new ingredient is the foil. Where the group’s earlier wire arrays gave one eruption, the foil gives four or five in a row about 30 nanoseconds apart, because plasma keeps closing the gap at the base and the current reconnects there. Each bubble travels faster than the last, up to 325 kilometres a second, and runs into the wreckage of the one before it, building shocks. The laboratory now has a jet that repeats itself.

Why it matters hereChapter 9 is about plasma that organises itself into a structure and holds it, and this is that at its most demanding: a magnetically pinched jet inside its own bubble, made and remade several times inside a single shot. Chapter 13 is where the laboratory and the sky are put on one footing — the same dimensionless numbers, the same reconnection at the base of the flow, the same knots downstream.

What it claims

01Magnetically driven, radiatively cooled plasma jets can be produced in a laboratory by a one megaamp, 250 nanosecond current pulse on the MAGPIE pulsed power facility. The jet is driven by the pressure of a toroidal magnetic field in a magnetic tower configuration: a magnetically collimated jet on the axis of a magnetic bubble that is confined by the ambient medium — the same picture Lynden-Bell proposed for jets from protostars to neutron stars.Abstract; Introduction, paragraphs 2 and 3
Published and peer-reviewed
02Replacing the radial wire array of the earlier experiments with a radial aluminium foil 6 to 6.5 microns thick, held between a 3.1 millimetre cathode and a 60 millimetre outer electrode, turns a single eruption into a repeating one: four or five successive magnetic tower outflows in one shot, emerging with a periodicity of about 30 nanoseconds and continuing for the duration of the current pulse.Abstract; Experimental setup; Formation of episodic magnetic tower jets, with Figure 3
Published and peer-reviewed
03The mechanism of the repetition is reconnection of current at the base of the cavity. The Lorentz force ablates the foil near the cathode and opens a radial gap of about 0.3 to 0.7 millimetres through which Poynting flux enters; plasma expanding from the cathode and the remaining foil closes that gap, the force on the closing plasma pushes it upward, and a new magnetic tower forms. The foil’s mass distribution, rising with radius rather than constant as in a wire array, is what makes the gap small enough to close quickly.Formation of episodic magnetic tower jets, closing paragraph
Published and peer-reviewed
04The cavities are measured, not inferred. Each bubble inflates radially at 50 to 60 kilometres per second and axially at 130 to 200, and each successive one is faster, reaching 325 kilometres per second for the third — consistent with the earlier episodes having swept the ambient plasma out of the way. Every episode is accompanied by a burst of soft x-rays, at photon energies of 200 to 300 electronvolts and above 800, correlated with the formation of the new jet, which says each episode begins with plasma pinching on the axis of the cavity.Formation of episodic magnetic tower jets, with Figure 4
Published and peer-reviewed
05With argon injected above the foil at an initial number density of ten to the seventeenth or eighteenth per cubic centimetre, the flow builds a shock structure of its own: a conical shock at about 60 degrees from the axis moving at 60 kilometres per second, which later splits into two oblique shocks; a faster, roughly spherical bow shock at 110 kilometres per second ahead of the hydrodynamic precursor jet; and a Mach stem where the two meet. The later magnetic bubbles, at around 300 kilometres per second, then overtake all of it. The ambient gas does not change the roughly 30 nanosecond periodicity of the jets.Jet propagation in an ambient gas, with Figure 5
Published and peer-reviewed
06What to watch: the authors report first measurements of trapped toroidal magnetic field inside the towers of about 0.5 tesla, implying a magnetic Reynolds number consistent with a jet temperature near 200 electronvolts from x-ray spectroscopy, and first estimates of the Poynting flux from an inductive probe across the gap. Some plasma parameters are yet to be measured accurately, so the case that the dimensionless numbers match those of jet launching from young stellar objects rests for now on the similarity to the earlier radial wire array experiments. The comparison the authors want tested is between current reconnection at the base of the laboratory jet and the accretion and reconnection thought to drive episodic outflows from young stars.Future directions
What to watch

Read it · abstract

Abstract

We report on experiments in which magnetically driven radiatively cooled plasma jets were produced by a 1 MA, 250 ns current pulse on the MAGPIE pulsed power facility. The jets were driven by the pressure of a toroidal magnetic field in a “magnetic tower” jet configuration. This scenario is characterized by the formation of a magnetically collimated plasma jet on the axis of a magnetic “bubble”, confined by the ambient medium. The use of a radial metallic foil instead of the radial wire arrays employed in our previous work allows for the generation of episodic magnetic tower outflows which emerge periodically on timescales of ~30 ns. The subsequent magnetic bubbles propagate with velocities reaching ~300 km/s and interact with previous eruptions leading to the formation of shocks.

F. Suzuki-Vidal, S. V. Lebedev, A. Ciardi, S. N. Bland, J. P. Chittenden, G. N. Hall, A. J. Harvey-Thompson, A. Marocchino, Cheng Ning, C. Stehlé, Adam Frank, Eric G. Blackman, S. C. Bott and T. P. Ray, Formation of episodic magnetically driven radiatively cooled plasma jets in the laboratory, chapter 4 of High Energy Density Laboratory Astrophysics 2008, Springer Netherlands, pages 19 to 23; also Astrophysics and Space Science 322, issue 1-4, pages 19 to 23 (2009). The authors’ preprint is arXiv:0904.0165.

(Abstract only — no other text of the paper is reproduced here; see the rights note above. On this site, the theory of how a fast rotator accelerates and collimates the plasma it ejects is at /library/stm-79d1cd725a, the wire-array plasma dynamics this group’s earlier experiments turned on is at /library/stm-704d7be815, and laboratory nanoflares from braided plasma loops — the same trick of building an astrophysical structure on a bench and watching it reconnect — are at /library/stm-d2628fac62.)

The way in

https://doi.org/10.1007/978-90-481-9999-0_4ONE PAPER, TWO RECORDS. The identifier on this page is the Springer book chapter, chapter 4 of High Energy Density Laboratory Astrophysics 2008 in the Astrophysics and Space Science Proceedings series. The same paper is also the journal article Astrophysics and Space Science volume 322, issue 1-4, pages 19 to 23 (2009), doi 10.1007/s10509-009-9981-1. Both are held closed by Springer and neither carries a Creative Commons licence. WHAT WAS READ. The authors’ own preprint, arXiv:0904.0165 version 1, submitted 1 April 2009, was downloaded and read in full on 2026-09-08; every claim below is located to one of its named sections or figures. arXiv distributes that posting under its non-exclusive distribution licence, which is a licence to arXiv and not an open licence, so this page stays abstract-only: the abstract below is the paper’s own and is the only text of it reproduced here. AUTHORS. The batch record printed four names in short form; they are corrected here to the forms the publisher record carries — A. J. Harvey-Thompson, Cheng Ning, C. Stehlé and T. P. Ray. Given names are expanded only where that record confirms them. AFFILIATIONS as printed on the preprint: Suzuki-Vidal, Lebedev, Bland, Chittenden, Hall, Harvey-Thompson, Marocchino and Ning at the Blackett Laboratory, Imperial College London; Ciardi and Stehlé at LERMA, Observatoire de Paris, CNRS and UPMC, Meudon; Frank and Blackman at the University of Rochester; Bott at the Center for Energy Research, University of California, San Diego; Ray at the Dublin Institute for Advanced Studies. The work was supported by the European Community Marie Curie JETSET network and by the Stewardship Science Academic Alliances programme of the National Nuclear Security Administration. RELATED PAGES: see the cross-links at the foot of this page.

How to cite it

Where it sits in the curriculum

Plasmoids, charge clusters and the orbs The unified picture