Showing 1–34 of 34 results for author: Ciardi, A

Experimental evidence for coronal mass ejection suppression in strong stellar magnetic fields

Authors: S. N. Chen, K. Burdonov, W. Yao, J. D. Alvarado-Gómez, C. Argiroffi, J. Béard, S. Bolanõs, R. Bonito, A. Ciardi, O. Cohen, J. J. Drake, S. Orlando, J. Fuchs

Abstract: Solar coronal mass ejections (CME) are routinely observed, but as of yet there exist few convincing detections of stellar CMEs. A reason for this could be the stronger magnetic fields of these stars, compared to that of our Sun, would prevent CME to form and escape. Here we combined astrophysical simulations, measurements of scaled high-energy laser-driven plasma flows, and 3D magneto-hydrodynamic… ▽ More Solar coronal mass ejections (CME) are routinely observed, but as of yet there exist few convincing detections of stellar CMEs. A reason for this could be the stronger magnetic fields of these stars, compared to that of our Sun, would prevent CME to form and escape. Here we combined astrophysical simulations, measurements of scaled high-energy laser-driven plasma flows, and 3D magneto-hydrodynamic modeling to test this hypothesis. Simulations show that in a 100 G stellar dipole field, low-plasma beta CMEs become magnetically confined. In the laboratory, a laser-produced plasma stream scaled to stellar CME conditions propagates freely at low applied magnetic fields (approximately 30 G stellar equivalent) but becomes unstable and halts entirely when the field is increased to 3e5 G (i.e., a 100 G equivalent). Numerical simulations suggest that the sudden disruption of the flow is induced by a kink instability. These results provide the first laboratory-scale evidence that strong stellar magnetic fields can fully suppress CME propagation, offering a physical explanation for their lack in stellar observations and highlighting the role of magnetic confinement in stellar evolution and exoplanet space weather. △ Less

Submitted 17 April, 2026; originally announced April 2026.

Simultaneous PW-scale laser driven MeV X-ray and neutron beam characterization for dual radiography capability

Authors: I. Cohen, W. Yao, N. Mirkovic, P. Antici, G. Auge, P. -G. Bleotu, T. Catabi, S. N. Chen, A. Ciardi, F. Condamine, E. d`Humieres, Q. Ducasse, G. Fauvel, R. Gambicchia, G. Giubega, L. Gremillet, M. Gugiu, V. Iancu, R. Leli`evre, L. T. Mix, Y. Ristic, D. Sangwan, M. Sheats, F. Trompier, L. Tudor , et al. (6 additional authors not shown)

Abstract: Laser-driven, high-brilliance secondary sources (electrons, ions, neutrons, X-rays) open new perspectives for compact material probing and imaging of high-speed events. A key advantage is their ability to perform multiplexed probing, as these sources are generated simultaneously in a single shot using a single laser beam. Here, we report the first quantitative measurements of photon spectra (0.1--… ▽ More Laser-driven, high-brilliance secondary sources (electrons, ions, neutrons, X-rays) open new perspectives for compact material probing and imaging of high-speed events. A key advantage is their ability to perform multiplexed probing, as these sources are generated simultaneously in a single shot using a single laser beam. Here, we report the first quantitative measurements of photon spectra (0.1--100 MeV) and angular distributions in the petawatt interaction regime, using an ultra-intense ($>10^{21}\,\rm W/cm^2$), ultra-short (24~fs) laser pulse. These results are complemented by the characterization of simultaneously produced MeV neutrons. We demonstrate that these neutrons, once moderated, can enable in-depth material identification via resonance transmission analysis. This work highlights the potential of compact, ultrashort-pulse PW lasers for dual neutron and X-ray radiography of dense materials. △ Less

Submitted 27 May, 2026; v1 submitted 14 April, 2026; originally announced April 2026.

Efficient ion re-acceleration in laboratory-produced interpenetrating collisionless shocks

Authors: W. Yao, I. Cohen, P. Suarez Gerona, H. Ahmed, A. F. A. Bott, S. N. Chen, M. Cook, R. Lelièvre, P. Martin, T. Waltenspiel, P. Antici, J. Béard, M. Borghesi, D. Caprioli, A. Ciardi, E. d'Humières, M. François, L. Gremillet, A. Marcowith, M. Miceli, T. Seebaruth, S. Orlando, J. Fuchs

Abstract: Although the origin of cosmic rays (CRs) remains an open question, collisionless magnetized shock waves are widely regarded as key sites for particle acceleration. Recent theories further suggest that shock-shock collisions in stellar clusters could provide the additional acceleration needed to explain the observed high-energy CR spectrum. Here, we investigate this hypothesis through a laser-based… ▽ More Although the origin of cosmic rays (CRs) remains an open question, collisionless magnetized shock waves are widely regarded as key sites for particle acceleration. Recent theories further suggest that shock-shock collisions in stellar clusters could provide the additional acceleration needed to explain the observed high-energy CR spectrum. Here, we investigate this hypothesis through a laser-based experiment that creates magnetized plasma conditions similar to astrophysical environments. Our results demonstrate that interpenetrating collisionless shocks can significantly boost the energy of ambient protons previously energized by the individual shocks, while also improving the overall acceleration efficiency. Numerical kinetic simulations corroborate these findings, revealing that protons are reaccelerated via their bouncing motion in the convective electric fields of the colliding magnetized flows. By allowing to highly energize ambient protons, our novel colliding-shock platform opens the prospect to test the long-discussed mechanism of diffusive shock acceleration in a controlled laboratory setting. △ Less

Submitted 26 June, 2026; v1 submitted 27 August, 2025; originally announced August 2025.

Interplay between the non-resonant streaming instability and self-generated pressure anisotropies

Authors: Alexis Marret, Andrea Ciardi, Roch Smets

Abstract: The non-thermal particles escaping from collisionless shocks into the surrounding medium can trigger a non-resonant streaming instability that converts parts of their drift kinetic energy into large amplitude magnetic field perturbations, and promote the confinement and acceleration of high energy cosmic rays. We present simulations of the instability using an hybrid-Particle-in-Cell approach incl… ▽ More The non-thermal particles escaping from collisionless shocks into the surrounding medium can trigger a non-resonant streaming instability that converts parts of their drift kinetic energy into large amplitude magnetic field perturbations, and promote the confinement and acceleration of high energy cosmic rays. We present simulations of the instability using an hybrid-Particle-in-Cell approach including Monte Carlo collisions, and demonstrate that the development of the non-resonant mode is associated with important ion pressure anisotropies in the background plasma. Depending on the initial conditions, the anisotropies may act on the instability by lowering its growth and trigger secondary micro-instabilities. Introducing collisions with neutrals yield a strong reduction of the magnetic field amplification as predicted by linear fluid theory. In contrast, Coulomb collisions in fully ionized plasmas are found to mitigate the self-generated pressure anisotropies and promote the growth of the magnetic field. △ Less

Submitted 22 July, 2024; originally announced July 2024.

Comments: arXiv admin note: text overlap with arXiv:2111.15272

Saturation of the compression of two interacting magnetic flux tubes evidenced in the laboratory

Authors: A. Sladkov, C. Fegan, W. Yao, A. F. A. Bott, S. N. Chen, H. Ahmed, E. D. Filippov, R. Lelièvre, P. Martin, A. McIlvenny, T. Waltenspiel, P. Antici, M. Borghesi, S. Pikuz, A. Ciardi, E. d'Humières, A. Soloviev, M. Starodubtsev, J. Fuchs

Abstract: Interactions between magnetic fields advected by matter play a fundamental role in the Universe at a diverse range of scales. A crucial role these interactions play is in making turbulent fields highly anisotropic, leading to observed ordered fields. These in turn, are important evolutionary factors for all the systems within and around. Despite scant evidence, due to the difficulty in measuring e… ▽ More Interactions between magnetic fields advected by matter play a fundamental role in the Universe at a diverse range of scales. A crucial role these interactions play is in making turbulent fields highly anisotropic, leading to observed ordered fields. These in turn, are important evolutionary factors for all the systems within and around. Despite scant evidence, due to the difficulty in measuring even near-Earth events, the magnetic field compression factor in these interactions, measured at very varied scales, is limited to a few. However, compressing matter in which a magnetic field is embedded, results in compression up to several thousands. Here we show, using laboratory experiments and matching three-dimensional hybrid simulations, that there is indeed a very effective saturation of the compression when two independent parallel-oriented magnetic fields regions encounter one another due to plasma advection. We found that the observed saturation is linked to a build-up of the magnetic pressure, which decelerates and redirects the inflows at their encounter point, thereby stopping further compression. Moreover, the growth of an electric field, induced by the incoming flows and the magnetic field, acts in redirecting the inflows transversely, further hampering field compression. △ Less

Submitted 29 November, 2024; v1 submitted 18 April, 2024; originally announced April 2024.

A "lighthouse" laser-driven staged proton accelerator allowing for ultrafast angular and spectral control

Authors: Vojtěch Horný, Konstantin Burdonov, Alice Fazzini, Vincent Lelasseux, Patrizio Antici, Sophia Nan Chen, Andrea Ciardi, Xavier Davoine, Emmanuel d'Humières, Laurent Gremillet, Ludovic Lecherbourg, François Mathieu, Dimitrios Papadopoulos, Weipeng Yao, Julien Fuchs

Abstract: Compact laser-plasma acceleration of fast ions has made great strides since its discovery over two decades ago, resulting in the current generation of high-energy ($\geq 100\,\rm MeV$) ultracold beams over ultrashort ($\leq 1\,\rm ps$) durations. To unlock broader applications of these beams, we need the ability to tailor the ion energy spectrum. Here, we present a scheme that achieves precisely t… ▽ More Compact laser-plasma acceleration of fast ions has made great strides since its discovery over two decades ago, resulting in the current generation of high-energy ($\geq 100\,\rm MeV$) ultracold beams over ultrashort ($\leq 1\,\rm ps$) durations. To unlock broader applications of these beams, we need the ability to tailor the ion energy spectrum. Here, we present a scheme that achieves precisely this by accelerating protons in a "lighthouse" fashion, whereby the highest-energy component of the beam is emitted in a narrow cone, well separated from the lower-energy components. This is made possible by a two-stage interaction in which the rear surface of the target is first set into rapid motion before the main acceleration phase. This approach offers the additional advantages of leveraging a robust sheath acceleration process in standard micron-thick targets and being optically controllable. △ Less

Submitted 17 April, 2024; originally announced April 2024.

Comments: 9 pages, 6 figures

Radiative cooling effects on reverse shocks formed by magnetised supersonic plasma flows

Authors: S. Merlini, J. D. Hare, G. C. Burdiak, J. W. D. Halliday, A. Ciardi, J. P. Chittenden, T. Clayson, A. J. Crilly, S. J. Eardley, K. E. Marrow, D. R. Russell, R. A. Smith, N. Stuart, L. G. Suttle, E. R. Tubman, V. Valenzuela-Villaseca, T. W. O. Varnish, S. V. Lebedev

Abstract: We study the structure of reverse shocks formed by the collision of supersonic, magnetised plasma flows driven by an inverse (or exploding) wire array with a planar conducting obstacle. We observe that the structure of these reverse shocks varies dramatically with wire material, despite the similar upstream flow velocities and mass densities. For aluminium wire arrays, the shock is sharp and well… ▽ More We study the structure of reverse shocks formed by the collision of supersonic, magnetised plasma flows driven by an inverse (or exploding) wire array with a planar conducting obstacle. We observe that the structure of these reverse shocks varies dramatically with wire material, despite the similar upstream flow velocities and mass densities. For aluminium wire arrays, the shock is sharp and well defined, consistent with magneto-hydrodynamic theory. In contrast, we do not observe a well-defined shock using tungsten wires, instead, we see a broad region dominated by density fluctuations on a wide range of spatial scales. We diagnose these two very different interactions using interferometry, Thomson scattering, shadowgraphy, and a newly developed imaging refractometer which is sensitive to small deflections of the probing laser corresponding to small-scale density perturbations. We conclude that the differences in shock structure are most likely due to radiative cooling instabilities which create small-scale density perturbations elongated along magnetic field lines in the tungsten plasma. These instabilities grow more slowly and are smoothed by thermal conduction in the aluminium plasma. △ Less

Submitted 7 August, 2023; v1 submitted 2 June, 2023; originally announced June 2023.

Journal ref: Phys. Plasmas 30, 092102 (2023)

Anisotropic Electron Heating in an Electron Cyclotron Resonance Thruster with Magnetic Nozzle

Authors: Jean Porto, Paul-Quentin Elias, Andrea Ciardi

Abstract: In a grid-less Electron Cyclotron Resonance (ECR) plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends of the perpendicular energy gained by the electrons. This work investigates the heating of the electrons by electromagnetic waves, taking their bouncing motion into account in a confining well formed by the magnetic mirror f… ▽ More In a grid-less Electron Cyclotron Resonance (ECR) plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends of the perpendicular energy gained by the electrons. This work investigates the heating of the electrons by electromagnetic waves, taking their bouncing motion into account in a confining well formed by the magnetic mirror force and the electrostatic potential of the thruster. An electromagnetic Particle-In-Cell (PIC) code is used to simulate the plasma in a magnetic field tube. The code's Maxwell solver is based on a semi-Lagrangian scheme known as the Constrained Interpolation Profile (CIP) which enables larger time steps. The results show that anisotropic plasma heating takes place exclusively inside the coaxial chamber, along a Doppler-broadened zone. It is also shown that a trapped population of electrons with a larger perpendicular energy exists in the plume. △ Less

Submitted 26 January, 2023; originally announced January 2023.

Dynamics of nanosecond laser pulse propagation and of associated instabilities in a magnetized underdense plasma

Authors: W. Yao, A. Higginson, J. -R. Marquès, P. Antici, J. Béard, K. Burdonov, M. Borghesi, A. Castan, A. Ciardi, B. Coleman, S. N. Chen, E. d'Humières, T. Gangolf, L. Gremillet, B. Khiar, L. Lancia, P. Loiseau, X. Ribeyre, A. Soloviev, M. Starodubtsev, Q. Wang, J. Fuchs

Abstract: The propagation and energy coupling of intense laser beams in plasmas are critical issues in laser-driven inertial confinement fusion. Applying magnetic fields to such a setup has been evoked to enhance fuel confinement and heating, and mitigate laser energy losses. Here we report on experimental measurements demonstrating improved transmission and increased smoothing of a high-power laser beam pr… ▽ More The propagation and energy coupling of intense laser beams in plasmas are critical issues in laser-driven inertial confinement fusion. Applying magnetic fields to such a setup has been evoked to enhance fuel confinement and heating, and mitigate laser energy losses. Here we report on experimental measurements demonstrating improved transmission and increased smoothing of a high-power laser beam propagating in an underdense magnetized plasma. We also measure enhanced backscattering, which our simulations show is due to hot electrons confinement, thus leading to reduced target preheating. △ Less

Submitted 11 November, 2022; originally announced November 2022.

PHARE : Parallel hybrid particle-in-cell code with patch-based adaptive mesh refinement

Authors: Nicolas Aunai, Roch Smets, Andrea Ciardi, Philip Deegan, Alexis Jeandet, Thibault Payet, Nathan Guyot, Loic Darrieumerlou

Abstract: Modeling multi-scale collisionless magnetized processes constitutes an important numerical challenge. By treating electrons as a fluid and ions kinetically, the so-called hybrid Particle-In-Cell (PIC) codes represent a promising intermediary between fully kinetic codes, limited to model small scales and short durations, and magnetohydrodynamic codes used large scale. However, simulating processes… ▽ More Modeling multi-scale collisionless magnetized processes constitutes an important numerical challenge. By treating electrons as a fluid and ions kinetically, the so-called hybrid Particle-In-Cell (PIC) codes represent a promising intermediary between fully kinetic codes, limited to model small scales and short durations, and magnetohydrodynamic codes used large scale. However, simulating processes at scales significantly larger than typical ion particle dynamics while resolving sub-ion dissipative current sheets remain extremely difficult. This paper presents a new hybrid PIC code with patch-based adaptive mesh refinement. Here, hybrid PIC equations are solved on a hierarchy of an arbitrary number of Cartesian meshes of incrementally finer resolution dynamically mapping regions of interest, and with a refined time stepping. This paper presents how the hybrid PIC algorithm is adapted to evolve such mesh hierarchy and the validation of the code on a uniform mesh, fixed refined mesh and dynamically refined mesh. △ Less

Submitted 14 October, 2023; v1 submitted 26 October, 2022; originally announced October 2022.

Investigating particle acceleration dynamics in interpenetrating magnetized collisionless super-critical shocks

Authors: W. Yao, A. Fazzini, S. N. Chen, K. Burdonov, J. Béard, M. Borghesi, A. Ciardi, M. Miceli, S. Orlando, X. Ribeyre, E. d'Humières, J. Fuchs

Abstract: Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. We have previously investigated particle acceleration induced by single super-critical shocks (whose magnetosonic Mach number is higher than the critical value of 2.7) (Yao et al. 2021, 2022), as well as the collision of two sub-critic… ▽ More Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. We have previously investigated particle acceleration induced by single super-critical shocks (whose magnetosonic Mach number is higher than the critical value of 2.7) (Yao et al. 2021, 2022), as well as the collision of two sub-critical shocks (Fazzini et al. 2022). Here, we propose to make measurements of accelerated particles from interpenetrating super-critical shocks to observe the ''phase-locking effect'' (Fazzini et al. 2022) from such an event. This effect is predicted to significantly boost the energy spectrum of the energized ions compared to a single supercritical collisionless shock. We thus anticipate that the results obtained in the proposed experiment could have a significant impact on our understanding of one type of primary source (acceleration of thermal ions as opposed to secondary acceleration mechanisms of already energetic ions) of ion energization of particles in the Universe. △ Less

Submitted 12 August, 2022; originally announced August 2022.

Optimizing laser coupling, matter heating, and particle acceleration from solids using multiplexed ultraintense lasers

Authors: Weipeng Yao, Motoaki Nakatsutsumi, Sébastien Buffechoux, Patrizio Antici, Macro Borghesi, Andrea Ciardi, Sophia N. Chen, Emmanuel d'Humières, Laurent Gremillet, Robert Heathcote, Vojtěch Horný, Paul McKenna, Mark N. Quinn, Lorenzo Romagnani, Ryan Royle, Gianluca Sarri, Yasuhiko Sentoku, Hans-Peter Schlenvoigt, Toma Toncian, Olivier Tresca, Laura Vassura, Oswald Willi, Julien Fuchs

Abstract: Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology limitations. Here, we investigate how to optimize their coupling with solid targets. Experimentally, we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation o… ▽ More Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology limitations. Here, we investigate how to optimize their coupling with solid targets. Experimentally, we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation of hot electrons at the target front and ion acceleration at the target backside. The underlying mechanisms are analyzed through multidimensional particle-in-cell simulations, revealing that the self-induced magnetic fields driven by the two laser beams at the target front are susceptible to reconnection, which is one possible mechanism to boost electron energization. In addition, the resistive magnetic field generated during the transport of the hot electrons in the target bulk tends to improve their collimation. Our simulations also indicate that such effects can be further enhanced by overlapping more than two laser beams. △ Less

Submitted 23 February, 2024; v1 submitted 12 August, 2022; originally announced August 2022.

Particle energization in colliding subcritical collisionless shocks investigated in the laboratory

Authors: A. Fazzini, W. Yao, K. Burdonov, J. Béard, S. N. Chen, A. Ciardi, E. d'Humières, R. Diab, E. D. Filippov, S. Kisyov, V. Lelasseux, M. Miceli, Q. Moreno, S. Orlando, S. Pikuz, X. Ribeyre, M. Starodubtsev, R. Zemskov, J. Fuchs

Abstract: Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. To investigate the detailed dynamics of this phenomenon, we have performed a dedicated laboratory experiment. We have generated two counter-streaming subcritical collisionless magnetized shocks by irradiating two teflon (CF$_2$) target… ▽ More Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. To investigate the detailed dynamics of this phenomenon, we have performed a dedicated laboratory experiment. We have generated two counter-streaming subcritical collisionless magnetized shocks by irradiating two teflon (CF$_2$) targets with 100 J, 1 ns laser beams on the LULI2000 laser facility. The interaction region between the plasma flows was pre-filled with a low density background hydrogen plasma and initialized with an externally applied homogeneous magnetic field perpendicular to the shocks. We report here on measurements of the plasma density and temperature during the formation of the supercritical shocks, their transition to subcritical, and final interpenetration. We have also modeled the macroscopic evolution of the system via hydrodynamic simulations and the microphysics at play during the interaction via Particle-In-Cell simulations. The main goal was to understand what was the effect of the second shock on particle energization. We found that in the presence of two shocks the ambient ions reach energies around 1.5 times of the ones obtained with single shocks. Both the presence of the downstream zone of the second shock and of the downstream zone common for the two shocks play a role in the different energization: the characteristics of the perpendicular electric fields in the two areas allow, indeed, certain particles to keep being accelerated or to avoid being decelerated. △ Less

Submitted 7 February, 2022; originally announced February 2022.

Enhancement of the non-resonant streaming instability by particle collisions

Authors: Alexis Marret, Andrea Ciardi, Roch Smets, Julien Fuchs, Loic Nicolas

Abstract: Streaming cosmic rays can power the exponential growth of a seed magnetic field by exciting a non-resonant instability that feeds on their bulk kinetic energy. By generating the necessary turbulent magnetic field, it is thought to play a key role in the confinement and acceleration of cosmic rays at shocks. In this work we present hybrid-Particle-In-Cell simulations of the non-resonant mode includ… ▽ More Streaming cosmic rays can power the exponential growth of a seed magnetic field by exciting a non-resonant instability that feeds on their bulk kinetic energy. By generating the necessary turbulent magnetic field, it is thought to play a key role in the confinement and acceleration of cosmic rays at shocks. In this work we present hybrid-Particle-In-Cell simulations of the non-resonant mode including Monte Carlo collisions, and investigate the interplay between the pressure anisotropies produced by the instability and particle collisions in the background plasma. Simulations of poorly ionized plasmas confirm the rapid damping of the instability by proton-neutral collisions predicted by linear fluid theory calculations. In contrast we find that Coulomb collisions in fully ionized plasmas do not oppose the growth of the magnetic field, but under certain conditions suppress the pressure anisotropies and actually enhance the magnetic field amplification. △ Less

Submitted 28 February, 2022; v1 submitted 30 November, 2021; originally announced November 2021.

Comments: Accepted to be published in Physical Review Letters

Characterization of the stability and dynamics of a laser-produced plasma expanding across strong magnetic field

Authors: Weipeng Yao, Julien Capitaine, Benjamin Khiar, Tommaso Vinci, Konstantin Burdonov, Jérôme Béard, Julien Fuchs, Andrea Ciardi

Abstract: Magnetized laser-produced plasmas are central to many new studies in laboratory astrophysics, inertial confinement fusion, and industrial applications. Here we present the results of large-scale, three-dimensional magneto-hydrodynamic simulations of the dynamics of a laser-produced plasma expanding into a transverse magnetic field with a strength of tens of Tesla. The simulations show the plasma i… ▽ More Magnetized laser-produced plasmas are central to many new studies in laboratory astrophysics, inertial confinement fusion, and industrial applications. Here we present the results of large-scale, three-dimensional magneto-hydrodynamic simulations of the dynamics of a laser-produced plasma expanding into a transverse magnetic field with a strength of tens of Tesla. The simulations show the plasma is confined by the strong magnetic field into a slender slab structured by the magnetized Rayleigh-Taylor instability that develops at the plasma-vacuum interface. We find that by perturbing the initial velocity of the plume the slab can develop kink-like motion which disrupts its propagation. △ Less

Submitted 28 May, 2021; originally announced May 2021.

Detailed characterization of laboratory magnetized super-critical collisionless shock and of the associated proton energization

Authors: W. Yao, A. Fazzini, S. N. Chen, K. Burdonov, P. Antici, J. Béard, S. Bolaños, A. Ciardi, R. Diab, E. D. Filippov, S. Kisyov, V. Lelasseux, M. Miceli, Q. Moreno, V. Nastasa, S. Orlando, S. Pikuz, D. C. Popescu, G. Revet, X. Ribeyre, E. d'Humières, J. Fuchs

Abstract: Collisionless shocks are ubiquitous in the Universe and are held responsible for the production of non-thermal particles and high-energy radiation. In the absence of particle collisions in the system, theoretical works show that the interaction of an expanding plasma with a pre-existing electromagnetic structure (as in our case) is able to induce energy dissipation and allow for shock formation. S… ▽ More Collisionless shocks are ubiquitous in the Universe and are held responsible for the production of non-thermal particles and high-energy radiation. In the absence of particle collisions in the system, theoretical works show that the interaction of an expanding plasma with a pre-existing electromagnetic structure (as in our case) is able to induce energy dissipation and allow for shock formation. Shock formation can alternatively take place when two plasmas interact, through microscopic instabilities inducing electromagnetic fields which are able in turn to mediate energy dissipation and shock formation. Using our platform where we couple a fast-expanding plasma induced by high-power lasers (JLF/Titan at LLNL and LULI2000) with high-strength magnetic fields, we have investigated the generation of magnetized collisionless shock and the associated particle energization. We have characterized the shock to be collisionless and super-critical. We report here on measurements of the plasma density, temperature, the electromagnetic field structures, and particle energization in the experiments, under various conditions of ambient plasma and B-field. We have also modeled the formation of the shocks using macroscopic hydrodynamic simulations and the associated particle acceleration using kinetic particle-in-cell simulations. As a companion paper of \citet{yao2020laboratory}, here we show additional results of the experiments and simulations, providing more information to reproduce them and demonstrating the robustness of our interpreted proton energization mechanism to be shock surfing acceleration. △ Less

Submitted 25 April, 2021; originally announced April 2021.

A new method to dispatch split particles in Particle-In-Cell codes

Authors: Roch Smets, Nicolas Aunais, ANdrea Ciardi, Matthieu Drouin, Martin Campos-Pino, Philip Deegan

Abstract: Particle-In-Cell codes are widely used for plasma physics simulations. It is often the case that particles within a computational cell need to be split to improve the statistics or, in the case of non-uniform meshes, to avoid the development of fictitious self-forces. Existing particle splitting methods are largely empirical and their accuracy in preserving the distribution function has not been e… ▽ More Particle-In-Cell codes are widely used for plasma physics simulations. It is often the case that particles within a computational cell need to be split to improve the statistics or, in the case of non-uniform meshes, to avoid the development of fictitious self-forces. Existing particle splitting methods are largely empirical and their accuracy in preserving the distribution function has not been evaluated in a quantitative way. Here we present a new method specifically designed for codes using adaptive mesh refinement. Although we point out that an exact, distribution function preserving method does exist, it requires a large number of split particles and its practical use is limited. We derive instead a method that minimizes the cost function representing the distance between the assignment function of the original particle and that of the sum of split particles. Depending on the interpolation degree and the dimension of the problem, we provide tabulated results for the weight and position of the split particles. This strategy represents no overhead in computing time and for a large enough number of split-particles it asymptotically tends to the exact solution. △ Less

Submitted 20 April, 2021; originally announced April 2021.

Journal ref: Computer Physics Communications, 2020

Laboratory evidence for proton energization by collisionless shock surfing

Authors: W. Yao, A. Fazzini, S. N. Chen, K. Burdonov, P. Antici, J. Béard, S. Bolaños, A. Ciardi, R. Diab, E. D. Filippov, S. Kisyov, V. Lelasseux, M. Miceli, Q. Moreno, V. Nastasa, S. Orlando, S. Pikuz, D. C. Popescu, G. Revet, X. Ribeyre, E. d'Humières, J. Fuchs

Abstract: Charged particles can be accelerated to high energies by collisionless shock waves in astrophysical environments, such as supernova remnants. By interacting with the magnetized ambient medium, these shocks can transfer energy to particles. Despite increasing efforts in the characterization of these shocks from satellite measurements at the Earth's bow shock and powerful numerical simulations, the… ▽ More Charged particles can be accelerated to high energies by collisionless shock waves in astrophysical environments, such as supernova remnants. By interacting with the magnetized ambient medium, these shocks can transfer energy to particles. Despite increasing efforts in the characterization of these shocks from satellite measurements at the Earth's bow shock and powerful numerical simulations, the underlying acceleration mechanism or a combination thereof is still widely debated. Here, we show that astrophysically relevant super-critical quasi-perpendicular magnetized collisionless shocks can be produced and characterized in the laboratory. We observe characteristics of super-criticality in the shock profile as well as the energization of protons picked up from the ambient gas to hundreds of keV. Kinetic simulations modelling the laboratory experiment identified shock surfing as the proton acceleration mechanism. Our observations not only provide the direct evidence of early stage ion energization by collisionless shocks, but they also highlight the role this particular mechanism plays in energizing ambient ions to feed further stages of acceleration. Furthermore, our results open the door to future laboratory experiments investigating the possible transition to other mechanisms, when increasing the magnetic field strength, or the effect induced shock front ripples could have on acceleration processes. △ Less

Submitted 30 June, 2021; v1 submitted 30 October, 2020; originally announced November 2020.

Enhanced x-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

Authors: E. D. Filippov, S. S. Makarov, K. F. Burdonov, W. Yao, G. Revet, J. Béard, S. Bolaños, S. N. Chen, A. Guediche, J. Hare, D. Romanovsky, I. Yu. Skobelev, M. Starodubtsev, A. Ciardi, S. A. Pikuz, J. Fuchs

Abstract: We analyze, using experiments and 3D MHD numerical simulations, the dynamics and radiative properties of a plasma ablated by a laser (1 ns, 10$^{12}$-10$^{13}$ W/cm$^2$) from a solid target, as it expands into a homogeneous, strong magnetic field (up to 30 T) transverse to its main expansion axis. We find that as soon as 2 ns after the start of the expansion, the plasma becomes constrained by the… ▽ More We analyze, using experiments and 3D MHD numerical simulations, the dynamics and radiative properties of a plasma ablated by a laser (1 ns, 10$^{12}$-10$^{13}$ W/cm$^2$) from a solid target, as it expands into a homogeneous, strong magnetic field (up to 30 T) transverse to its main expansion axis. We find that as soon as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe a dense slab that rapidly expands into vacuum after ~ 8 ns; however, this slab contains only ~ 2 % of the total plasma. As a result of the higher density and increased heating of the confined plasma, there is a net enhancement of the total x-ray emissivity induced by the magnetization. △ Less

Submitted 22 June, 2020; originally announced June 2020.

Comments: 15 pages, 4 figures, Supplementary Information, submitted to PRL

Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field

Authors: G. Revet, B. Khiar, E. Filippov, C. Argiroffi, J. Béard, R. Bonito, M. Cerchez, S. N. Chen, T. Gangolf, D. P. Higginson, A. Mignone, B. Olmi, M. Ouillé, S. N. Ryazantsev, I. Yu. Skobelev, M. I. Safronova, M. Starodubtsev, T. Vinci, O. Willi, S. Pikuz, S. Orlando, A. Ciardi, J. Fuchs

Abstract: The shaping of astrophysical outflows into bright, dense and collimated jets due to magnetic pressure is here investigated using laboratory experiments. We notably look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growin… ▽ More The shaping of astrophysical outflows into bright, dense and collimated jets due to magnetic pressure is here investigated using laboratory experiments. We notably look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun's outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field. △ Less

Submitted 20 December, 2020; v1 submitted 21 April, 2020; originally announced April 2020.

Laser-produced magnetic-Rayleigh-Taylor unstable plasma slabs in a 20 T magnetic field

Authors: B. Khiar, G. Revet, A. Ciardi, K. Burdonov, E. Filippov, J. Béard, M. Cerchez, S. N. Chen, T. Gangolf, S. S. Makarov, M. Ouillé, M. Safronova, I. Yu. Skobelev, A. Soloviev, M. Starodubtsev, O. Willi, S. Pikuz, J. Fuchs

Abstract: Magnetized laser-produced plasmas are central to many novel laboratory astrophysics and inertial confinement fusion studies, as well as in industrial applications. Here we provide the first complete description of the three-dimensional dynamics of a laser-driven plasma plume expanding in a 20 T transverse magnetic field. The plasma is collimated by the magnetic field into a slender, rapidly elonga… ▽ More Magnetized laser-produced plasmas are central to many novel laboratory astrophysics and inertial confinement fusion studies, as well as in industrial applications. Here we provide the first complete description of the three-dimensional dynamics of a laser-driven plasma plume expanding in a 20 T transverse magnetic field. The plasma is collimated by the magnetic field into a slender, rapidly elongating slab, whose plasma-vacuum interface is unstable to the growth of the "classical", fluid-like magnetized Rayleigh-Taylor instability. △ Less

Submitted 30 October, 2019; originally announced October 2019.

Comments: Accepted for publication in Physical Review Letters

Journal ref: Phys. Rev. Lett. 123, 205001 (2019)

Laser experiment for the study of accretion dynamics of Young Stellar Objects: design and scaling

Authors: G. Revet, B. Khiar, J. Béard, R. Bonito, S. Orlando, M. V. Starodubtsev, A. Ciardi, J. Fuchs

Abstract: A new experimental set-up designed to investigate the accretion dynamics in newly born stars is presented. It takes advantage of a magnetically collimated stream produced by coupling a laser-generated expanding plasma to a $2\times 10^{5}~{G}\ (20~{T})$ externally applied magnetic field. The stream is used as the accretion column and is launched onto an obstacle target that mimics the stellar surf… ▽ More A new experimental set-up designed to investigate the accretion dynamics in newly born stars is presented. It takes advantage of a magnetically collimated stream produced by coupling a laser-generated expanding plasma to a $2\times 10^{5}~{G}\ (20~{T})$ externally applied magnetic field. The stream is used as the accretion column and is launched onto an obstacle target that mimics the stellar surface. This setup has been used to investigate in details the accretion dynamics, as reported in [G. Revet et al., Science Advances 3, e1700982 (2017), arXiv:1708.02528}. Here, the characteristics of the stream are detailed and a link between the experimental plasma expansion and a 1D adiabatic expansion model is presented. Dimensionless numbers are also calculated in order to characterize the experimental flow and its closeness to the ideal MHD regime. We build a bridge between our experimental plasma dynamics and the one taking place in the Classical T Tauri Stars (CTTSs), and we find that our set-up is representative of a high plasma $β$ CTTS accretion case. △ Less

Submitted 26 September, 2019; v1 submitted 2 September, 2019; originally announced September 2019.

Journal ref: High Energy Density Phys. 33 (2019) 100711

Interactions of magnetized plasma flows in pulsed-power driven experiments

Authors: L G Suttle, G C Burdiak, C L Cheung, T Clayson, J W D Halliday, J D Hare, S Rusli, D Russell, E Tubman, A Ciardi, N F Loureiro, J Li, A Frank, S V Lebedev

Abstract: A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the JxB acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving current. This setup has been used for a variety of exper… ▽ More A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the JxB acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving current. This setup has been used for a variety of experiments investigating the interactions of magnetized plasma flows. In experiments designed to investigate magnetic reconnection, the collision of counter-streaming flows, carrying oppositely directed magnetic fields, leads to the formation of a reconnection layer in which we observe ions reaching temperatures much greater than predicted by classical heating mechanisms. The breakup of this layer under the plasmoid instability is dependent on the properties of the inflowing plasma, which can be controlled by the choice of the wire array material. In other experiments, magnetized shocks were formed by placing obstacles in the path of the magnetized plasma flow. The pile-up of magnetic flux in front of a conducting obstacle produces a magnetic precursor acting on upstream electrons at the distance of the ion inertial length. This precursor subsequently develops into a steep density transition via ion-electron fluid decoupling. Obstacles which possess a strong private magnetic field affect the upstream flow over a much greater distance, providing an extended bow shock structure. In the region surrounding the obstacle the magnetic pressure holds off the flow, forming a void of plasma material, analogous to the magnetopause around planetary bodies with self-generated magnetic fields. △ Less

Submitted 22 July, 2019; originally announced July 2019.

Comments: 46th EPS conference on Plasma Physics, Milan, Italy 2019

Ion heating and magnetic flux pile-up in a magnetic reconnection experiment with super-Alfvenic plasma inflows

Authors: L. G. Suttle, J. D. Hare, S. V. Lebedev, A. Ciardi, N. F. Loureiro, G. C. Burdiak, J. P. Chittenden, T. Clayson, J. W. D. Halliday, N. Niasse, D. Russell, F. Suzuki Vidal, E. Tubman, T. Lane, J. Ma, T. Robinson, R. A. Smith, N. Stuart

Abstract: This work presents a magnetic reconnection experiment in which the kinetic, magnetic and thermal properties of the plasma each play an important role in the overall energy balance and structure of the generated reconnection layer. Magnetic reconnection occurs during the interaction of continuous and steady flows of super-Alfvenic, magnetized, aluminum plasma, which collide in a geometry with two-d… ▽ More This work presents a magnetic reconnection experiment in which the kinetic, magnetic and thermal properties of the plasma each play an important role in the overall energy balance and structure of the generated reconnection layer. Magnetic reconnection occurs during the interaction of continuous and steady flows of super-Alfvenic, magnetized, aluminum plasma, which collide in a geometry with two-dimensional symmetry, producing a stable and long-lasting reconnection layer. Optical Thomson scattering measurements show that when the layer forms, ions inside the layer are more strongly heated than electrons, reaching temperatures of Ti~ZTe>300 eV - much greater than can be expected from strong shock and viscous heating alone. Later in time, as the plasma density in the layer increases, the electron and ion temperatures are found to equilibrate, and a constant plasma temperature is achieved through a balance of the heating mechanisms and radiative losses of the plasma. Measurements from Faraday rotation polarimetry also indicate the presence of significant magnetic field pile-up occurring at the boundary of the reconnection region, which is consistent with the super-Alfvenic velocity of the inflows. △ Less

Submitted 27 February, 2018; originally announced February 2018.

Comments: 15 pages, 8 figures, 1 table

An Experimental Platform for Pulsed-Power Driven Magnetic Reconnection

Authors: J. D. Hare, L. G. Suttle, S. V. Lebedev, N. F. Loureiro, A. Ciardi, J. P. Chittenden, T. Clayson, S. J. Eardley, C. Garcia, J. W. D. Halliday, T. Robinson, R. A. Smith, N. Stuart, F. Suzuki-Vidal, E. R. Tubman

Abstract: We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on exploding wire arrays driven in parallel [Suttle, L. G. et al. PRL, 116, 225001]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow evolution o… ▽ More We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on exploding wire arrays driven in parallel [Suttle, L. G. et al. PRL, 116, 225001]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer which forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes, and asymmetric reconnection. △ Less

Submitted 12 January, 2018; v1 submitted 17 November, 2017; originally announced November 2017.

Comments: 14 pages, 9 figures. Version revised to include referee's comments. Submitted to Physics of Plasmas

Laboratory unravelling of matter accretion in young stars

Authors: G. Revet, S. N. Chen, R. Bonito, B. Khiar, E. Filippov, C. Argiroffi, D. P. Higginson, S. Orlando, J. Béard, M. Blecher, M. Borghesi, K. Burdonov, D. Khaghani, K. Naughton, H. Pépin, O. Portugall, R. Riquier, R. Rodriguez, S. N. Ryazantsev, I. Yu. Skobelev, A. Soloviev, O. Willi, S. Pikuz, A. Ciardi, J. Fuchs

Abstract: Accretion dynamics in the forming of young stars is still object of debate because of limitations in observations and modelling. Through scaled laboratory experiments of collimated plasma accretion onto a solid in the presence of a magnetic field, we open first window on this phenomenon by tracking, with spatial and temporal resolution, the dynamics of the system and simultaneously measuring multi… ▽ More Accretion dynamics in the forming of young stars is still object of debate because of limitations in observations and modelling. Through scaled laboratory experiments of collimated plasma accretion onto a solid in the presence of a magnetic field, we open first window on this phenomenon by tracking, with spatial and temporal resolution, the dynamics of the system and simultaneously measuring multiband emissions. We observe in these experiments that matter, upon impact, is laterally ejected from the solid surface, then refocused by the magnetic field toward the incoming stream. Such ejected matter forms a plasma shell that envelops the shocked core, reducing escaped X-ray emission. This demonstrates one possible structure reconciling current discrepancies between mass accretion rates derived from X-ray and optical observations. △ Less

Submitted 8 August, 2017; originally announced August 2017.

Formation and Structure of a Current Sheet in Pulsed-Power Driven Magnetic Reconnection Experiments

Authors: J. D. Hare, S. V. Lebedev, L. G. Suttle, N. F. Loureiro, A. Ciardi, G. C. Burdiak, J. P. Chittenden, T. Clayson, S. J. Eardley, C. Garcia, J. W. D. Halliday, N. Niasse, T. Robinson, R. A. Smith, N. Stuart, F. Suzuki-Vidal, G. F. Swadling, J. Ma, J. Wu

Abstract: We describe magnetic reconnection experiments using a new, pulsed-power driven experimental platform in which the inflows are super-sonic but sub-Alfvénic.The intrinsically magnetised plasma flows are long lasting, producing a well-defined reconnection layer that persists over many hydrodynamic time scales.The layer is diagnosed using a suite of high resolution laser based diagnostics which provid… ▽ More We describe magnetic reconnection experiments using a new, pulsed-power driven experimental platform in which the inflows are super-sonic but sub-Alfvénic.The intrinsically magnetised plasma flows are long lasting, producing a well-defined reconnection layer that persists over many hydrodynamic time scales.The layer is diagnosed using a suite of high resolution laser based diagnostics which provide measurements of the electron density, reconnecting magnetic field, inflow and outflow velocities and the electron and ion temperatures.Using these measurements we observe a balance between the power flow into and out of the layer, and we find that the heating rates for the electrons and ions are significantly in excess of the classical predictions. The formation of plasmoids is observed in laser interferometry and optical self-emission, and the magnetic O-point structure of these plasmoids is confirmed using magnetic probes. △ Less

Submitted 13 September, 2017; v1 submitted 30 May, 2017; originally announced May 2017.

Comments: 14 pages, 12 figures. Accepted for publication in Physics of Plasmas

Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment

Authors: J. D. Hare, L. Suttle, S. V. Lebedev, N. F. Loureiro, A. Ciardi, G. C. Burdiak, J. P. Chittenden, T. Clayson, C. Garcia, N. Niasse, T. Robinson, R. A. Smith, N. Stuart, F. Suzuki-Vidal, G. F. Swadling, J. Ma, J. Wu, Q. Yang

Abstract: We present a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. Oppositely directed magnetic fields $(B=3$ T), advected by supersonic, sub-Alfvénic carbon plasma flows $(V_{in}=50$ km/s), are brought together and mutually annihilate inside a thin current layer ($δ=0.6$ mm). Temporally and spatially resolved optical diagnostics, including i… ▽ More We present a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. Oppositely directed magnetic fields $(B=3$ T), advected by supersonic, sub-Alfvénic carbon plasma flows $(V_{in}=50$ km/s), are brought together and mutually annihilate inside a thin current layer ($δ=0.6$ mm). Temporally and spatially resolved optical diagnostics, including interferometry, Faraday rotation imaging and Thomson scattering, allow us to determine the structure and dynamics of this layer, the nature of the inflows and outflows and the detailed energy partition during the reconnection process. We measure high electron and ion temperatures $(T_e=100$ eV, $T_i=600$ eV), far in excess of what can be attributed to classical (Spitzer) resistive and viscous dissipation. We observe the repeated formation and ejection of plasmoids, which we interpret as evidence of two-fluid effects in our experiment. △ Less

Submitted 25 January, 2017; v1 submitted 29 September, 2016; originally announced September 2016.

Comments: Accepted for publication in PRL, expected 17th Febuary 2017. 6 pages, 5 figures

Journal ref: Phys. Rev. Lett. 118, 085001 (2017)

Bow shock fragmentation driven by a thermal instability in laboratory-astrophysics experiments

Authors: F. Suzuki-Vidal, S. V. Lebedev, A. Ciardi, L. A. Pickworth, R. Rodriguez, J. M. Gil, G. Espinosa, P. Hartigan, G. F. Swadling, J. Skidmore, G. N. Hall, M. Bennett, S. N. Bland, G. Burdiak, P. de Grouchy, J. Music, L. Suttle, E. Hansen, A. Frank

Abstract: The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counter-streaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinches driven by the current pulse from the MAGPIE puls… ▽ More The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counter-streaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinches driven by the current pulse from the MAGPIE pulsed-power generator. The jets have different flow velocities in the laboratory frame and the experiments are driven over many times the characteristic cooling time-scale. The initially smooth bow shock rapidly develops small-scale non-uniformities over temporal and spatial scales that are consistent with a thermal instability triggered by strong radiative cooling in the shock. The growth of these perturbations eventually results in a global fragmentation of the bow shock front. The formation of a thermal instability is supported by analysis of the plasma cooling function calculated for the experimental conditions with the radiative packages ABAKO/RAPCAL. △ Less

Submitted 9 November, 2015; v1 submitted 22 September, 2015; originally announced September 2015.

Comments: 9 pages, 5 figures, Accepted for publication in The Astrophysical Journal on 5th November 2015

MSC Class: 85-05 ACM Class: J.2.1, J.2.9

Astrophysics of magnetically collimated jets generated from laser-produced plasmas

Authors: A. Ciardi, T. Vinci, J. Fuchs, B. Albertazzi, C. Riconda, H. Pépin, O. Portugall

Abstract: The generation of astrophysically relevant jets, from magnetically collimated, laser-produced plasmas, is investigated through three-dimensional, magneto-hydrodynamic simulations. We show that for laser intensities I ~ 10^12 - 10^14 W/cm^2, a magnetic field in excess of ~ 0.1 MG, can collimate the plasma plume into a prolate cavity bounded by a shock envelope with a standing conical shock at its t… ▽ More The generation of astrophysically relevant jets, from magnetically collimated, laser-produced plasmas, is investigated through three-dimensional, magneto-hydrodynamic simulations. We show that for laser intensities I ~ 10^12 - 10^14 W/cm^2, a magnetic field in excess of ~ 0.1 MG, can collimate the plasma plume into a prolate cavity bounded by a shock envelope with a standing conical shock at its tip, which re-collimates the flow into a super magneto-sonic jet beam. This mechanism is equivalent to astrophysical models of hydrodynamic inertial collimation, where an isotropic wind is focused into a jet by a confining circumstellar torus-like envelope. The results suggest an alternative mechanism for a large-scale magnetic field to produce jets from wide-angle winds. (abridged version) △ Less

Submitted 12 December, 2012; originally announced December 2012.

Comments: Accepted for publication in Physical Review Letters. 5 pages, 4 figures

Numerical study of jets produced by conical wire arrays on the Magpie pulsed power generator

Authors: M. Bocchi, J. P. Chittenden, A. Ciardi, F. Suzuki-Vidal, G. N. Hall, P. de Grouchy, S. V. Lebedev, S. C. Bott

Abstract: The aim of this work is to model the jets produced by conical wire arrays on the MAGPIE generator, and to design and test new setups to strengthen the link between laboratory and astrophysical jets. We performed the modelling with direct three-dimensional magneto-hydro-dynamic numerical simulations using the code GORGON. We applied our code to the typical MAGPIE setup and we successfully reproduce… ▽ More The aim of this work is to model the jets produced by conical wire arrays on the MAGPIE generator, and to design and test new setups to strengthen the link between laboratory and astrophysical jets. We performed the modelling with direct three-dimensional magneto-hydro-dynamic numerical simulations using the code GORGON. We applied our code to the typical MAGPIE setup and we successfully reproduced the experiments. We found that a minimum resolution of approximately 100 is required to retrieve the unstable character of the jet. We investigated the effect of changing the number of wires and found that arrays with less wires produce more unstable jets, and that this effect has magnetic origin. Finally, we studied the behaviour of the conical array together with a conical shield on top of it to reduce the presence of unwanted low density plasma flows. The resulting jet is shorter and less dense. △ Less

Submitted 10 March, 2011; originally announced March 2011.

Comments: Accepted for publication in Astrophysics & Space Science. HEDLA 2010 conference procedings. Final pubblication will be available on Springer

Experimental Studies of Magnetically Driven Plasma Jets

Authors: F. Suzuki-Vidal, S. V. Lebedev, S. N. Bland, G. N. Hall, G. Swadling, A. J. Harvey-Thompson, G. Burdiak, P. de Grouchy, J. P. Chittenden, A. Marocchino, M. Bocchi, A. Ciardi, A. Frank, S. C. Bott

Abstract: We present experimental results on the formation of supersonic, radiatively cooled jets driven by pressure due to the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which a jet on the axis of a magnetic cavity is collimated by a toroidal magnetic field as… ▽ More We present experimental results on the formation of supersonic, radiatively cooled jets driven by pressure due to the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which a jet on the axis of a magnetic cavity is collimated by a toroidal magnetic field as it expands into the ambient medium. The jets in the experiments have similar Mach number, plasma beta and cooling parameter to those in protostellar jets. Additionally the Reynolds, magnetic Reynolds and Peclet numbers are much larger than unity, allowing the experiments to be scaled to astrophysical flows. The experimental configuration allows for the generation of episodic magnetic cavities, suggesting that periodic fluctuations near the source may be responsible for some of the variability observed in astrophysical jets. Preliminary measurements of kinetic, magnetic and Poynting energy of the jets in our experiments are presented and discussed, together with estimates of their temperature and trapped toroidal magnetic field. △ Less

Submitted 10 December, 2010; originally announced December 2010.

Comments: 7 pages, 6 figures, accepted for publication in Astrophysics & Space Science

Journal ref: Astrophysics and Space Science, November 2011, Volume 336, Issue 1, pp 41-46

Formation of Episodic Magnetically Driven Radiatively Cooled Plasma Jets in the Laboratory

Authors: F. Suzuki-Vidal, S. V. Lebedev, A. Ciardi, S. N. Bland, J. P. Chittenden, G. N. Hall, A. Harvey-Thompson, A. Marocchino, C. Ning, C. Stehle, A. Frank, E. G. Blackman, S. C. Bott, T. Ray

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 ''bubbl… ▽ More 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. △ Less

Submitted 1 April, 2009; originally announced April 2009.

Comments: 6 pages, 5 figures. Accepted for publication in Astrophysics & Space Science

Journal ref: Astrophys.Space Sci.322:19-23,2009

Laboratory Studies of Astrophysical Jets

Authors: Andrea Ciardi

Abstract: Jets and outflows produced during star-formation are observed on many scales: from the "micro-jets" extending a few hundred Astronomical Units to the "super-jets" propagating to parsecs distances. Recently, a new "class" of short-lived (hundreds of nano-seconds) centimetre-long jets has emerged in the laboratory as a complementary tool to study these complex astrophysical flows. Here I will disc… ▽ More Jets and outflows produced during star-formation are observed on many scales: from the "micro-jets" extending a few hundred Astronomical Units to the "super-jets" propagating to parsecs distances. Recently, a new "class" of short-lived (hundreds of nano-seconds) centimetre-long jets has emerged in the laboratory as a complementary tool to study these complex astrophysical flows. Here I will discuss and review the recent work done on "simulating" protostellar jets in the laboratory using z-pinch machines. △ Less

Submitted 2 March, 2009; originally announced March 2009.

Comments: 25 Pages, 11 Figures to appear in Lecture Notes in Physics. Series Title: Jets from young stars IV: From models to observations and experiments Editors: P. J. V. Garcia and J. M. T. Ferreira. Publisher: Springer

Journal ref: Lect.Notes Phys.793:31-50,2010