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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…
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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.
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Submitted 7 February, 2022;
originally announced February 2022.
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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…
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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.
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Submitted 25 April, 2021;
originally announced April 2021.
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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…
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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.
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Submitted 30 June, 2021; v1 submitted 30 October, 2020;
originally announced November 2020.
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Expansion of a radially symmetric blast shell into a uniformly magnetized plasma
Authors:
M E Dieckmann,
Q Moreno,
D Doria,
L Romagnani,
G Sarri,
D Folini,
R Walder,
A Bret,
E d'Humieres,
M Borghesi
Abstract:
The expansion of a thermal pressure-driven radial blast shell into a dilute ambient plasma is examined with two-dimensional PIC simulations. The purpose is to determine if laminar shocks form in a collisionless plasma that resemble their magnetohydrodynamic counterparts. The ambient plasma is composed of electrons with the temperature 2 keV and cool fully ionized nitrogen ions. It is permeated by…
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The expansion of a thermal pressure-driven radial blast shell into a dilute ambient plasma is examined with two-dimensional PIC simulations. The purpose is to determine if laminar shocks form in a collisionless plasma that resemble their magnetohydrodynamic counterparts. The ambient plasma is composed of electrons with the temperature 2 keV and cool fully ionized nitrogen ions. It is permeated by a spatially uniform magnetic field. A forward shock forms between the shocked ambient medium and the pristine ambient medium, which changes from an ion acoustic one through a slow magnetosonic one to a fast magnetosonic shock with increasing shock propagation angles relative to the magnetic field. The slow magnetosonic shock that propagates obliquely to the magnetic field changes into a tangential discontinuity for a perpendicular propagation direction, which is in line with the magnetohydrodynamic model. The expulsion of the magnetic field by the expanding blast shell triggers an electron-cyclotron drift instability.
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Submitted 8 May, 2018;
originally announced May 2018.
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Quasi-perpendicular fast magnetosonic shock with wave precursor in collisionless plasma
Authors:
Q. Moreno,
M. E. Dieckmann,
X. Ribeyre,
E. d'Humières
Abstract:
A one-dimensional particle-in-cell (PIC) simulation tracks a fast magnetosonic shock over time scales comparable to an inverse ion gyrofrequency. The magnetic pressure is comparable to the thermal pressure upstream. The shock propagates across a uniform background magnetic field with a pressure that equals the thermal pressure upstream at the angle 85$^\circ$ at a speed that is 1.5 times the fast…
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A one-dimensional particle-in-cell (PIC) simulation tracks a fast magnetosonic shock over time scales comparable to an inverse ion gyrofrequency. The magnetic pressure is comparable to the thermal pressure upstream. The shock propagates across a uniform background magnetic field with a pressure that equals the thermal pressure upstream at the angle 85$^\circ$ at a speed that is 1.5 times the fast magnetosonic speed in the electromagnetic limit. Electrostatic contributions to the wave dispersion increase its phase speed at large wave numbers, which leads to a convex dispersion curve. A fast magnetosonic precursor forms ahead of the shock with a phase speed that exceeds the fast magnetosonic speed by about $\sim 30 \%$. The wave is slower than the shock and hence it is damped.
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Submitted 7 May, 2018;
originally announced May 2018.
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Impact of the electron to ion mass ratio on unstable systems in particle-in-cell simulations
Authors:
Quentin Moreno,
Mark Eric Dieckmann,
Xavier Ribeyre,
Sophie Jequier,
Vladimir Tikhonchuk,
Emmanuel d'Humières
Abstract:
The evolution of the Buneman and two-stream instabilities driven by a cold dilute mildly relativistic electron beam is studied as a function of the ion\'\s charge-to-mass ratio. The growth rates of both instabilities are comparable for the selected parameters if the charge-to-mass ratio of protons is used and the Buneman instability outgrows the two-stream instability for a larger ratio. Particle-…
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The evolution of the Buneman and two-stream instabilities driven by a cold dilute mildly relativistic electron beam is studied as a function of the ion\'\s charge-to-mass ratio. The growth rates of both instabilities are comparable for the selected parameters if the charge-to-mass ratio of protons is used and the Buneman instability outgrows the two-stream instability for a larger ratio. Particle-in-cell (PIC) simulations show that both instabilities grow independently during their linear growth phase. The much lower saturation amplitude of the Buneman instability implies that it saturates first even if the linear growth rates of both instabilities are equal. The electron phase space holes it drives coalesce. Their spatial size increases in time and they start interacting with the two-stream mode, which triggers the onset of electrostatic turbulence. A reduced charge-to-mass ratio results in stronger turbulence and ion heating and in an increased energy loss of the relativistic electron beam compared to that in a simulation with the correct ratio.
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Submitted 12 June, 2018; v1 submitted 6 March, 2018;
originally announced March 2018.