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Dieckmann, M. E. & Bret, A. (2018). Electrostatic and magnetic instabilities in the transition layer of a collisionless weakly relativistic pair shock. Monthly notices of the Royal Astronomical Society, 473(1), 198-209
Open this publication in new window or tab >>Electrostatic and magnetic instabilities in the transition layer of a collisionless weakly relativistic pair shock
2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 1, p. 198-209Article in journal (Refereed) Published
Abstract [en]

Energetic electromagnetic emissions by astrophysical jets like those that are launched during the collapse of a massive star and trigger gamma-ray bursts are partially attributed to relativistic internal shocks. The shocks are mediated in the collisionless plasma of such jets by the filamentation instability of counterstreaming particle beams. The filamentation instability grows fastest only if the beams move at a relativistic relative speed. We model here with a particle-in-cell simulation, the collision of two cold pair clouds at the speed c/2 (c: speed of light). We demonstrate that the two-stream instability outgrows the filamentation instability for this speed and is thus responsible for the shock formation. The incomplete thermalization of the upstream plasma by its quasi-electrostatic waves allows other instabilities to grow. A shock transition layer forms, in which a filamentation instability modulates the plasma far upstream of the shock. The inflowing upstream plasma is progressively heated by a two-stream instability closer to the shock and compressed to the expected downstream density by the Weibel instability. The strong magnetic field due to the latter is confined to a layer 10 electron skin depths wide.

Place, publisher, year, edition, pages
Oxford University Press, 2018
Keywords
relativistic pair jet, collisionless instability, PIC simulations
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:liu:diva-141947 (URN)10.1093/mnras/stx2387 (DOI)000415653600017 ()
Note

Funding agencies: Ministerio de Educacion y Ciencia, Spain [ENE2013-45661-C2-1-P, ENE2016-75703-R]; Junta de Comunidades de Castilla-La Mancha [PEII-2014-008-P]; Grand Equipement National de Calcul Intensif (GENCI) [x2016046960]

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2017-12-12Bibliographically approved
Dieckmann, M. E., Alejo, A. & Sarri, G. (2018). Expansion of a mildly relativistic hot pair cloud into an electron-proton plasma. Physics of Plasmas, 25(6), Article ID 062122.
Open this publication in new window or tab >>Expansion of a mildly relativistic hot pair cloud into an electron-proton plasma
2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 6, article id 062122Article in journal (Refereed) Published
Abstract [en]

The expansion of a charge-neutral cloud of electrons and positrons with the temperature 1 MeV into an unmagnetized ambient plasma is examined with a 2D particle-in-cell simulation. The pair outflow drives solitary waves in the ambient protons. Their bipolar electric fields attract electrons of the outflowing pair cloud and repel positrons. These fields can reflect some of the protons, thereby accelerating them to almost an MeV. Ion acoustic solitary waves are thus an efficient means to couple energy from the pair cloud to protons. The scattering of the electrons and positrons by the electric field slows down their expansion to a nonrelativistic speed. Only a dilute pair outflow reaches the expansion speed expected from the cloud's thermal speed. Its positrons are more energetic than its electrons. In time, an instability grows at the front of the dense slow-moving part of the pair cloud, which magnetizes the plasma. The instability is driven by the interaction of the outflowing positrons with the protons. These results shed light on how magnetic fields are created and ions are accelerated in pair-loaded astrophysical jets and winds.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
Keywords
PIC simulation, pair plasma, filamentation instability
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-148878 (URN)10.1063/1.5036954 (DOI)000437193700036 ()
Available from: 2018-06-21 Created: 2018-06-21 Last updated: 2018-08-13
Dieckmann, M. E., Moreno, Q., Doria, D., Romagnani, L., Sarri, G., Folini, D., . . . Borghesi, M. (2018). Expansion of a radially symmetric blast shell into a uniformly magnetized plasma. Physics of Plasmas, 25(5), Article ID 052108.
Open this publication in new window or tab >>Expansion of a radially symmetric blast shell into a uniformly magnetized plasma
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2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 5, article id 052108Article in journal (Refereed) Published
Abstract [en]

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 which resemble their magnetohydrodynamic counterparts. The ambient plasma is composed of electrons with the temperature of 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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
Keywords
PIC simulation, shock, magnetized plasma
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-147775 (URN)10.1063/1.5024851 (DOI)000433961800010 ()2-s2.0-85046898862 (Scopus ID)
Note

Funding agencies: Grand Equipement National de Calcul Intensif (GENCI) [x2016046960, A0010506129]; EPSRC [EP/P02212X/1, EP/N027175/1]; CRAL (ENS de Lyon); French National Program for High Energy (PNHE)

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-06-28Bibliographically approved
Moreno, Q., Dieckmann, M. E., Ribeyre, X., Jequier, S., Tikhonchuk, V. & d'Humieres, E. (2018). Impact of the electron to ion mass ratio on unstable systems in particle-in-cell simulations. Physics of Plasmas, 25(6), Article ID 062125.
Open this publication in new window or tab >>Impact of the electron to ion mass ratio on unstable systems in particle-in-cell simulations
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2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 6, article id 062125Article in journal (Refereed) Published
Abstract [en]

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-to-electron mass ratio. The growth rates of both instabilities are comparable for the selected parameters if the realistic ion-to-electron mass ratio is used and the Buneman instability outgrows the two-stream instability for an artificially reduced mass ratio. Particle-in-cell 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 results in the growth of electrostatic waves over a broad range of wave numbers. A reduced ion-to-electron mass ratio results in increased ion heating and in an increased energy loss of the relativistic electron beam compared to that in a simulation with the correct mass ratio.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
Keywords
PIC simulation, beam instability
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-149657 (URN)10.1063/1.5027913 (DOI)000437193700039 ()2-s2.0-85049080685 (Scopus ID)
Available from: 2018-07-16 Created: 2018-07-16 Last updated: 2018-08-28Bibliographically approved
Dieckmann, M. E., Alejo, A., Sarri, G., Folini, D. & Walder, R. (2018). One-dimensional thermal pressure-driven expansion of a pair cloud into an electron-proton plasma. Physics of Plasmas, 25(5), Article ID 064502.
Open this publication in new window or tab >>One-dimensional thermal pressure-driven expansion of a pair cloud into an electron-proton plasma
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2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 5, article id 064502Article in journal (Refereed) Published
Abstract [en]

Recently, a filamentation instability was observed when a laser-generated pair cloud interacted with an ambient plasma. The magnetic field it drove was strong enough to magnetize and accelerate the ambient electrons. It is of interest to determine if and how pair cloud-driven instabilities can accelerate ions in the laboratory or in astrophysical plasma. For this purpose, the expansion of a localized pair cloud with the temperature 400 keV into a cooler ambient electron-proton plasma is studied by means of one-dimensional particle-in-cell simulations. The cloud's expansion triggers the formation of electron phase space holes that accelerate some protons to MeV energies. Forthcoming lasers might provide the energy needed to create a cloud that can accelerate protons.

Place, publisher, year, edition, pages
Melville, NY, United States: A I P Publishing LLC, 2018
Keywords
Particle simulation, pair clouds, plasma instability
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-148179 (URN)10.1063/1.5026568 (DOI)000437193700131 ()064502 (PubMedID)
Note

Funding agencies: CRAL (Centre de Recherche Astrophysique de Lyon, CRAL, Universite de Lyon); French National Program of High Energy (PNHE); EPSRC [EP/N027175/1]

Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-07-27Bibliographically approved
Moreno, Q., Dieckmann, M. E., Ribeyre, X. & d'Humieres, E. (2018). Quasi-perpendicular fast magnetosonic shock with wave precursor in collisionless plasma. Physics of Plasmas, 25(7), Article ID 074502.
Open this publication in new window or tab >>Quasi-perpendicular fast magnetosonic shock with wave precursor in collisionless plasma
2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 7, article id 074502Article in journal (Refereed) Published
Abstract [en]

A one-dimensional particle-in-cell simulation tracks a fast magnetosonic shock over time scales comparable with 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° 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 ∼30%. The wave is slower than the shock, and hence, it is damped.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
Keywords
PIC simulation, magnetized plasma shocks, precursor wave
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-149658 (URN)10.1063/1.5039478 (DOI)000440589100096 ()2-s2.0-85049728737 (Scopus ID)
Available from: 2018-07-16 Created: 2018-07-16 Last updated: 2018-08-28Bibliographically approved
Bret, A., Pe'er, A., Sironi, L., Dieckmann, M. E. & Narayan, R. (2017). Departure from MHD prescriptions in shock formation over a guiding magnetic field. Laser and particle beams (Print), 35, 513-519
Open this publication in new window or tab >>Departure from MHD prescriptions in shock formation over a guiding magnetic field
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2017 (English)In: Laser and particle beams (Print), ISSN 0263-0346, E-ISSN 1469-803X, Vol. 35, p. 513-519Article in journal (Refereed) Published
Abstract [en]

In plasmas where the mean-free-path is much larger than the size of the system, shock waves can arise with a front much shorter than the mean-free path. These so-called "collisionless shocks" are mediated y collective plasma interactions. Studies conducted so far on these shocks found that although binary collisions are absent, the distribution functions are thermalized downstream by scattering on the fields, so that magnetohydrodynamic prescriptions may apply. Here we show a clear departure from this pattern in the case of Weibel shocks forming over a flow-aligned magnetic field. A micro-physical analysis of the particle motion in the Weibel filaments shows how they become unable to trap the flow in the presence of too strong a field, inhibiting the mechanism of shock formation. Particle-in-cell simulations confirm these results.

Place, publisher, year, edition, pages
Cambridge University Press, 2017
Keywords
plasma shock, kinetic theory, PIC simulation
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-140164 (URN)10.1017/S0263034617000519 (DOI)000409042200017 ()
Note

Funding agencies: European Union Seventh Framework Program [618499]; NASA [NNX12AO83G, TCAN NNX14AB47G, NAS8-03060]; NASA - Chandra X-ray Center [PF4-150126];  [ENE2013-45661-C2-1-P];  [PEII-2014-008-P];  [ANR-14-CE33-0019 MACH];  [SNIC2015-1-305]

Available from: 2017-09-02 Created: 2017-09-02 Last updated: 2017-11-03Bibliographically approved
Dieckmann, M. E., Folini, D., Walder, R., Romagnani, L., d'Humieres, E., Bret, A., . . . Ynnerman, A. (2017). Emergence of MHD structures in a collisionless PIC simulation plasma. Physics of Plasmas, 24(9), Article ID 094502.
Open this publication in new window or tab >>Emergence of MHD structures in a collisionless PIC simulation plasma
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2017 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, no 9, article id 094502Article in journal (Refereed) Published
Abstract [en]

The expansion of a dense plasma into a dilute plasma across an initially uniform perpendicular magnetic field is followed with a one-dimensional particle-in-cell simulation over magnetohydrodynamics time scales. The dense plasma expands in the form of a fast rarefaction wave. The accelerated dilute plasma becomes separated from the dense plasma by a tangential discontinuity at its back. A fast magnetosonic shock with the Mach number 1.5 forms at its front. Our simulation demonstrates how wave dispersion widens the shock transition layer into a train of nonlinear fast magnetosonic waves.

Place, publisher, year, edition, pages
Melville, NY, United States: A I P Publishing LLC, 2017
Keywords
PIC simulation, fast magnetosonic shock
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-140648 (URN)10.1063/1.4991702 (DOI)000412107400120 ()
Note

Funding agencies: CRAL; Grand Equipement National de Calcul Intensif (GENCI) [x2016046960]

Available from: 2017-09-06 Created: 2017-09-06 Last updated: 2017-11-03Bibliographically approved
Dieckmann, M. E., Doria, D., Ahmed, H., Romagnani, L., Sarri, G., Folini, D., . . . Borghesi, M. (2017). Expansion of a radial plasma blast shell into an ambient plasma. Physics of Plasmas, 24(9), Article ID 094501.
Open this publication in new window or tab >>Expansion of a radial plasma blast shell into an ambient plasma
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2017 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, no 9, article id 094501Article in journal (Refereed) Published
Abstract [en]

The expansion of a radial blast shell into an ambient plasma is modeled with a particle-in-cell simulation. The unmagnetized plasma consists of electrons and protons. The formation and evolution of an electrostatic shock is observed, which is trailed by ion-acoustic solitary waves that grow on the beam of the blast shell ions in the post-shock plasma. In spite of the initially radial symmetric outflow, the solitary waves become twisted and entangled and, hence, they break the radial symmetry of the flow. The waves and their interaction with the shocked ambient ions slow down the blast shell protons and bring the post-shock plasma closer to equilibrium.

Place, publisher, year, edition, pages
Melville, NY, United States: A I P Publishing LLC, 2017
Keywords
Laser plasma, PIC simulation, collisionless shock, solitary waves
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-140165 (URN)10.1063/1.4991694 (DOI)000412107400119 ()
Available from: 2017-09-02 Created: 2017-09-02 Last updated: 2017-11-03Bibliographically approved
Bret, A. & Dieckmann, M. E. (2017). Hierarchy of instabilities for two counter-streaming magnetized pair beams: Influence of field obliquity. Physics of Plasmas, 24(6), Article ID 062105.
Open this publication in new window or tab >>Hierarchy of instabilities for two counter-streaming magnetized pair beams: Influence of field obliquity
2017 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, no 6, article id 062105Article in journal (Refereed) Published
Abstract [en]

The hierarchy of unstable modes when two counter-streaming pair plasmas interact over a flow-aligned magnetic field has been recently investigated [Phys. Plasmas 23, 062122 (2016)]. The analysis is here extended to the case of an arbitrarily tilted magnetic field. The two plasma shells are initially cold and identical. For any angle θ ∈ [0, π/2] between the field and the initial flow, the hierarchy of unstable modes is numerically determined in terms of the initial Lorentz factor of the shells γ0, and the field strength as measured by a parameter denoted σ. For θ = 0, four different kinds of mode are likely to lead the linear phase. The hierarchy simplifies for larger θ's, partly because the Weibel instability can no longer be cancelled in this regime. For θ > 0.78 (44°) and in the relativistic regime, the Weibel instability always govern the interaction. In the non-relativistic regime, the hierarchy becomes θ-independent because the interaction turns to be field-independent. As a result, the two-stream instability becomes the dominant one, regardless of the field obliquity.

Place, publisher, year, edition, pages
A I P Publishing LLC, 2017
Keywords
instabilities, plasma waves, magnetic field
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-138195 (URN)10.1063/1.4985321 (DOI)000404639000010 ()
Note

Funding agencies: Ministerio de Educacion y Ciencia, Spain [ENE2013-45661-C2-1-P, ENE2016-75703-R]; Junta de Comunidades de Castilla-La Mancha [PEII-2014-008-P]

Available from: 2017-06-12 Created: 2017-06-12 Last updated: 2017-11-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4055-0552

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