liu.seSearch for publications in DiVA
Change search
Link to record
Permanent link

Direct link
BETA
Alternative names
Publications (10 of 120) Show all publications
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., 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
Show others...
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
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
Show others...
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)
Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-06-20Bibliographically 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
Show others...
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
Show others...
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
Show others...
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
Dieckmann, M. E., Sarri, G., Doria, D., Ynnerman, A. & Borghesi, M. (2016). Particle-in-cell simulation study of a lower-hybrid shock. Physics of Plasmas, 23(6), 062111
Open this publication in new window or tab >>Particle-in-cell simulation study of a lower-hybrid shock
Show others...
2016 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 23, no 6, p. 062111-Article in journal (Refereed) Published
Abstract [en]

The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell simulations. The magnetic field points perpendicular to the plasmas expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma. Published by AIP Publishing.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-130440 (URN)10.1063/1.4953568 (DOI)000379172200017 ()
Note

Funding Agencies|EPSRC [EP/N022696/1]

Available from: 2016-08-15 Created: 2016-08-05 Last updated: 2017-11-28
Marcowith, A., Bret, A., Bykov, A., Dieckmann, M. E., Drury, L., Lembege, B., . . . Stockem Novo, A. (2016). The microphysics of collisionless shock waves. Reports on progress in physics (Print), 79(4), Article ID 046901.
Open this publication in new window or tab >>The microphysics of collisionless shock waves
Show others...
2016 (English)In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 79, no 4, article id 046901Article, review/survey (Refereed) Published
Abstract [en]

Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:liu:diva-126458 (URN)10.1088/0034-4885/79/4/046901 (DOI)000373216700006 ()27007555 (PubMedID)
Note

Funding agencies: ISSI; french ANR MACH project; Ministerio de Educacion y Ciencia, Spain [ENE2013-45661-C2-1-P]; Junta de Comunidades de Castilla-La Mancha, Spain [PEII-2014-008-P]

Available from: 2016-03-26 Created: 2016-03-26 Last updated: 2017-11-30
Bret, A., Stockem Novo, A., Narayan, R., Ruyer, C., Dieckmann, M. E. & Silva, L. O. (2016). Theory of the formation of a collisionless Weibel shock: pair vs. electron/proton plasmas. Laser and particle beams (Print), 34(2), 362-367
Open this publication in new window or tab >>Theory of the formation of a collisionless Weibel shock: pair vs. electron/proton plasmas
Show others...
2016 (English)In: Laser and particle beams (Print), ISSN 0263-0346, E-ISSN 1469-803X, Vol. 34, no 2, p. 362-367Article in journal (Refereed) Published
Abstract [en]

Collisionless shocks are shocks in which the mean-free path is much larger than the shock front. They are ubiquitous in astrophysics and the object of much current attention as they are known to be excellent particle accelerators that could be the key to the cosmic rays enigma. While the scenario leading to the formation of a fluid shock is well known, less is known about the formation of a collisionless shock. We present theoretical and numerical results on the formation of such shocks when two relativistic and symmetric plasma shells (pair or electron/proton) collide. As the two shells start to interpenetrate, the overlapping region turns Weibel unstable. A key concept is the one of trapping time τp, which is the time when the turbulence in the central region has grown enough to trap the incoming flow. For the pair case, this time is simply the saturation time of the Weibel instability. For the electron/proton case, the filaments resulting from the growth of the electronic and protonic Weibel instabilities, need to grow further for the trapping time to be reached. In either case, the shock formation time is 2τp in two-dimensional (2D), and 3τp in 3D. Our results are successfully checked by particle-in-cell simulations and may help designing experiments aiming at producing such shocks in the laboratory.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-127503 (URN)10.1017/S0263034616000197 (DOI)000378358100019 ()
Available from: 2016-05-27 Created: 2016-04-28 Last updated: 2017-11-30
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4055-0552

Search in DiVA

Show all publications