Observation of collisionless shocks in a large current‐free laboratory plasma

Niemann, C.; Gekelman, Walter; Constantin, Carmen; Everson, E. T.; Schaeffer, D. B.; Bondarenko, A. S.; Clark, S. E.; Winske, D.; Vincena, S.; Compernolle, B. Van; Pribyl, Patrick

doi:10.1002/2014gl061820

Cited by 80 publications

(66 citation statements)

References 25 publications

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“…In this proceeding, we present measurements of the resonant right-hand instability in our experiment and compare them with predictions of shock-formation theory [17]. This research continues previous work on the generation and investigation of a perpendicular collisionless shock [18,19]. …”

supporting

confidence: 72%

Towards a parallel collisionless shock in LAPD

Weidl¹,

Heuer²,

Schaeffer³

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. Using a high-energy laser to produce a super-Alfvénic carbon-ion beam in a strongly magnetized helium plasma, we expect to be able to observe the formation of a collisionless parallel shock inside the Large Plasma Device. We compare early magneticfield measurements of the resonant right-hand instability with analytical predictions and find excellent agreement. Hybrid simulations show that the carbon ions couple to the background plasma and compress it, although so far the background ions are mainly accelerated perpendicular to the mean-field direction. IntroductionCollisionless shocks are a virtually ubiquitous phenomenon in space, from planetary bow shocks in our solar system [1,2,3,4,5] to the shocks occurring in supernova remnants [6,7] and presumably the jets of active galactic nuclei [8]. Our understanding of the complex process of shock formation has greatly improved since Sagdeev's seminal paper [9], thanks to both satellite observations [10,11] and numerical simulations [12,13]. Yet the complicated three-dimensional structure that one would predict for a parallel shock on theoretical grounds [14] is difficult to confirm, either because of the nature of one-or few-point satellite measurements or because three-dimensional kinetic simulations are computationally too expensive.To avoid these particular difficulties, our group is working on producing a parallel collisionless shock in a laser-plasma experiment at the Large Plasma Device (LAPD) [15]. Simulations assuming a quasi-one-dimensional carbon front [16] showed that the available energy density is sufficient to observe the early stages of collisionless-shock formation. In this proceeding, we present measurements of the resonant right-hand instability in our experiment and compare them with predictions of shock-formation theory [17]. This research continues previous work on the generation and investigation of a perpendicular collisionless shock [18,19].

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supporting

confidence: 72%

Towards a parallel collisionless shock in LAPD

Weidl¹,

Heuer²,

Schaeffer³

et al. 2017

J. Phys.: Conf. Ser.

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“…However, this process has never before been observed in a laboratory setting. Despite numerous experiments utilizing laser-produced plasmas to simulate space and astrophysical explosions 22 , including noteworthy recent studies that successfully generated magnetized collisionless shocks 23,24 and measured the electrostatic component of the electric field structure associated with an explosive plasma cloud 25,26 , none of these efforts examined the ion dynamics in sufficient detail to confirm Larmor coupling as a participating momentum exchange mechanism.…”

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confidence: 99%

Collisionless momentum transfer in space and astrophysical explosions

et al. 2017

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The AMPTE (Active Magnetospheric Particle Tracer Explorers) mission provided in situ measurements of collisionless momentum and energy exchange between an artificial, photo-ionized barium plasma cloud and the streaming, magnetized hydrogen plasma of the solar wind [1][2][3] . One of its most significant findings was the unanticipated displacement of the barium ion 'comet head' (and an oppositely directed deflection of the streaming hydrogen ions) transverse to both the solar wind flow and the interplanetary magnetic field, defying the conventional expectation that the barium ions would simply move downwind , a collisionless momentum exchange mechanism believed to occur in various astrophysical and space-plasma environments 10,11 and to participate in cosmic magnetized collisionless shock formation [12][13][14] . Here we present the detection of Larmor coupling in a reproducible laboratory experiment that combines an explosive laser-produced plasma cloud with preformed, magnetized ambient plasma in a parameter regime relevant to the AMPTE barium releases. In our experiment, time-resolved Doppler spectroscopy reveals ambient ion acceleration transverse to both the laser-produced plasma flow and the background magnetic field. Utilizing a detailed numerical simulation, we demonstrate that the ambient ion velocity distribution corresponding to the measured Doppler-shifted spectrum is qualitatively and quantitatively consistent with Larmor coupling.The AMPTE barium release experiments aimed to better understand a ubiquitous category of astrophysical and space phenomena characterized by the rapid expansion or relative motion of a dense 'debris' plasma cloud through relatively tenuous, magnetized, ambient plasma. Examples include the expansion of stellar material through the surrounding interstellar medium in supernova remnants 10 , the formation of cometary plasma tails due to the solar wind 15 , the interaction of interplanetary coronal mass ejections with the Earth's magnetosphere 16 , and man-made ionospheric explosions 17 . In these rarified environments, the Coulomb collisional mean free paths exceed the observed interaction length scales by many orders of magnitude, signifying that the debris plasma exchanges momentum and energy with the ambient plasma via collisionless, collective, electromagnetic effects. In addition, the relative motion of the debris cloud produces electric polarization fields between the magnetically confined electrons and the relatively freestreaming ions, resulting in E × B drift electron currents that expel the magnetic field within the cloud volume (the diamagnetic cavity) and enhance it at the cloud edge (the magnetic compression) 18 . The general evolution in the reference frame of the magnetized ambient plasma is thus a deceleration of the debris cloud as it couples to the ambient plasma via collisionless processes and deforms the magnetic field.We here consider explosive astrophysical and space environments characterized by a perpendicular-to-B debris plasma flow speed V d that exceed...

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“…Successful generation of collisionless MHD [45,46] and ES shocks, and experimental approach to study collisionless EM shock [60][61][62]64,65] in laboratory indicate that laboratory experiment can be an alternative approach to study space and astrophysical plasma physics. Furthermore, recent achievement of mono-energetic proton acceleration by collisionless ES shock produced by ultrahigh-intensity laser system [84][85][86] shows a possibility to apply the collisionless shock to several applications including medical treatment.…”

Section: Discussionmentioning

confidence: 99%

“…Recentry, Niemann et al have reported the first observation [45,46] of collisionless MHD perpendicular shock, which was predicted by hybrid-simulation [47], using the Large Plasma Device [48] and a high-energy laser system [49]. No clear particle acceleration has been investigated experimentally for the MHD shock yet.…”

Section: Introductionmentioning

confidence: 99%

Collisionless electrostatic shock generation using high-energy laser systems

Sakawa

Morita

Kuramitsu

et al. 2016

Advances in Physics: X

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Collisionless shock is ubiquitous in space and astrophysical plasmas, and is believed to be a source of cosmic rays. In this review article, historical achievements of three different types of collisionless shocks, i.e. magnetohydrodynamic, electromagnetic, and electrostatic (ES) shocks, in theory/simulation, observation in space and astrophysical plasmas, and laboratory experiments are shown. An overview is given on recent progress of collisionless ES shock experiments using high-energy laser systems for two schemes. One is an interaction between laser-produced highdensity ablating plasma and a low-density ambient plasma, and the other is an interaction between laser-ablated counterstreaming plasmas using double-plane target. For the former scheme, detailed measurements of structures of collisionless ES shock and ion-acoustic soliton, and the transition from double-layer to collisionless ES shock are conducted by proton radiography. For the latter scheme, optical diagnostics are used to observe global structures of plasmas and shocks; collective laser Thomson scattering method is applied to clarify local plasma parameters, such as electron and ion temperatures, flow velocity, and electron density; and proton radiography is employed to measure a shock electric field. The measured large density-jump, steepening of self-emission profile, plasma parameters in the upand down-stream regions of a shock, and the narrow width of the shock electric field compared with the ion-ion Coulomb meanfree-path reveal the evidence for the formation of collisionless ES shock. ARTICLE HISTORY

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Observation of collisionless shocks in a large current‐free laboratory plasma

Cited by 80 publications

References 25 publications

Towards a parallel collisionless shock in LAPD

Towards a parallel collisionless shock in LAPD

Collisionless momentum transfer in space and astrophysical explosions

Collisionless electrostatic shock generation using high-energy laser systems

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