Experimental study of collisionless super-Alfvénic interaction of interpenetrating plasma flows

Шайхисламов, И. Ф.; Zakharov, Yu. P.; Posukh, V. G.; Мелехов, А. В.; Boyarintsev, E. L.; Ponomarenko, A. G.; Terekhin, V. A.

doi:10.1134/s1063780x15050050

Cited by 21 publications

(16 citation statements)

References 21 publications

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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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confidence: 99%

Collisionless momentum transfer in space and astrophysical explosions

et al. 2017

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“…Its presence and influence should be visible by direct detection of the polarization field as in Ref. 33 or the asymmetric response of the ambient plasma across V m of the passing MLPP as is the case in Ref. 35.…”

Section: Or Any Other Dimensionless Parameters Associated With Additimentioning

confidence: 97%

“…Many are conducted such that the majority of debris is directed unilaterally away from the target and across the background magnetic field. 5,6,[28][29][30][31][32][33][34][35] This configuration includes the presence of a polarization field, which arises from the center-of-mass motion of the expanding plasma. If the center-of-mass moves with velocity V m , then the polarization field has the approximate strength E pol ¼ ÀV m Â B.…”

Section: Or Any Other Dimensionless Parameters Associated With Additimentioning

confidence: 99%

Collisionless coupling of a high-β expansion to an ambient, magnetized plasma. I. Rayleigh model and scaling

Bonde

2018

Physics of Plasmas

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The dynamics of a magnetized, expanding plasma with a high ratio of kinetic energy density to ambient magnetic field energy density, or b, are examined by adapting a model of gaseous bubbles expanding in liquids as developed by Lord Rayleigh. New features include scale magnitudes and evolution of the electric fields in the system. The collisionless coupling between the expanding and ambient plasma due to these fields is described as well as the relevant scaling relations. Several different responses of the ambient plasma to the expansion are identified in this model, and for most laboratory experiments, ambient ions should be pulled inward, against the expansion due to the dominance of the electrostatic field.

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“…Over the last several decades, a number of such experiments have achieved significant progress by combining explosive, laser-produced debris plasmas with preformed, magnetized ambient plasmas. 18 Utilizing this configuration, recent investigations have successfully driven magnetized collisionless shocks into the ambient plasma [19][20][21] and measured the electrostatic electric field structures associated with the explosive debris plasma cloud, 22,23 providing indirect evidence of the collisionless debris-ambient interaction. However, none of these efforts examined the ion dynamics in sufficient detail to directly verify collisionless coupling through the laminar electric field structure proposed by the previous theoretical and numerical studies.…”

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confidence: 99%

Laboratory study of collisionless coupling between explosive debris plasma and magnetized ambient plasma

et al. 2017

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The explosive expansion of a localized plasma cloud into a relatively tenuous, magnetized, ambient plasma characterizes a variety of astrophysical and space phenomena. In these rarified environments, collisionless electromagnetic processes rather than Coulomb collisions typically mediate the transfer of momentum and energy from the expanding “debris” plasma to the surrounding ambient plasma. In an effort to better understand the detailed physics of collisionless coupling mechanisms, compliment in situ measurements of space phenomena, and provide validation of previous computational and theoretical work, the present research jointly utilizes the Large Plasma Device and the Raptor laser facility at the University of California, Los Angeles to study the super-Alfvénic, quasi-perpendicular expansion of laser-produced carbon (C) and hydrogen (H) debris plasma through preformed, magnetized helium (He) ambient plasma via a variety of diagnostics, including emission spectroscopy, wavelength-filtered imaging, and a magnetic flux probe. Doppler shifts detected in a He1+ ion spectral line indicate that the ambient ions initially accelerate transverse to both the debris plasma flow and the background magnetic field. A qualitative analysis in the framework of a “hybrid” plasma model (kinetic ions and inertia-less fluid electrons) demonstrates that the ambient ion trajectories are consistent with the large-scale laminar electric field expected to develop due to the expanding debris. In particular, the transverse ambient ion motion provides direct evidence of Larmor coupling, a collisionless momentum exchange mechanism that has received extensive theoretical and numerical investigation. In order to quantitatively evaluate the observed Doppler shifts, a custom simulation utilizing a detailed model of the laser-produced debris plasma evolution calculates the laminar electric field and computes the initial response of a distribution of ambient test ions. A synthetic Doppler-shifted spectrum constructed from the simulated test ion velocities excellently reproduces the experimental measurements, verifying that the observed ambient ion motion corresponds to collisionless coupling through the laminar electric field.

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Experimental study of collisionless super-Alfvénic interaction of interpenetrating plasma flows

Cited by 21 publications

References 21 publications

Collisionless momentum transfer in space and astrophysical explosions

Collisionless momentum transfer in space and astrophysical explosions

Collisionless coupling of a high-β expansion to an ambient, magnetized plasma. I. Rayleigh model and scaling

Laboratory study of collisionless coupling between explosive debris plasma and magnetized ambient plasma

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