Expansion of a radially symmetric blast shell into a uniformly magnetized plasma

Dieckmann, Mark E; Moreno, Q.; Doria, D.; Romagnani, L.; Sarri, Gianluca; Folini, Doris; Walder, Rolf; Bret, Antoine; d’Humières, E.; Borghesi, M.

doi:10.1063/1.5024851

Cited by 12 publications

(6 citation statements)

References 39 publications

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“…2a) in which the shape of the shock surface differs significantly from a planar one. It should be noted, that we have not observed different shock velocities maintained over the whole time of the simulation for perpendicular and parallel regions, which was reported in Dieckmann et al (2018). While the settings are different, another reason may be that the accelerated particles in our simulations overpressure the foreshock medium in the quasi-parallel propagation regime, thus compensating for the magnetic compressibility in the quasi-perpendicular regime.…”

Section: Simulation Resultssupporting

confidence: 51%

“…Very recently the results of hydrodynamic modeling of the obliquity-dependent acceleration in a spherically expanding blast waves for different magnetic field morphologies have been reported (Pais et al 2018). Earlier hybrid and fully kinetic particle-in-cell simulations of shocks with variable obliquity have been focused either on the interaction between the solar wind and a planetary magnetic field (Omidi et al 2005;Blanco-Cano et al 2009) or the simulations were initialized with a radially expanding blast shell (Dieckmann et al 2018). While the expanding blast shell set-up resembles a spherically expanding SNR shock, it is computationally not feasible to follow its evolution over long enough timescales and observe the acceleration of ions to high energies.…”

Section: Simulation Set-upmentioning

confidence: 99%

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Steepening of Cosmic-Ray Spectra in Shocks with Varying Magnetic Field Direction

Hanusch

Liseykina

Malkov

et al. 2019

ApJ

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Cosmic ray (CR) spectra, both measured upon their arrival at the Earth's atmosphere and inferred from the emission in supernova remnants (SNRs), appear to be significantly steeper than the "standard" diffusive shock acceleration (DSA) theory predicts. Although the reconstruction of the primary spectra introduces an additional steepening due to propagation effects, there is a growing consensus in the CR community that these corrections fall short to explain the newest high-precision data. Using 2D hybrid simulations, we investigate a new mechanism that may steepen the spectrum during the acceleration in SNR shocks.Most of the DSA treatments are limited to homogeneous shock environments. To investigate whether inhomogeneity effects can produce the necessary extra steepening, we assume that the magnetic field changes its angle along the shock front. The rationale behind this approach is the strong dependence of the DSA efficiency upon the field angle, θ Bn . Our results show that the variation of shock obliquity along its face results in a noticeable steepening of the DSA spectrum. Compared to simulations of quasi-parallel shocks, we observe an increase of the spectral index by ∆q = 0.1 − 0.15. Possible extrapolation of the limited simulation results to more realistic SNR conditions are briefly considered.

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Section: Simulation Resultssupporting

confidence: 51%

Section: Simulation Set-upmentioning

confidence: 99%

Steepening of Cosmic-Ray Spectra in Shocks with Varying Magnetic Field Direction

Hanusch

Liseykina

Malkov

et al. 2019

ApJ

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“…Such instabilities have also been observed at discontinuities between an expanding plasma and an ambient plasma in space plasmas 29 and in simulations of laser-generated plasma. 30 The following picture emerged. Close to the injection boundary, positrons contributed most of the positive charge.…”

Section: Discussionmentioning

confidence: 99%

Two-dimensional particle simulation of the boundary between a hot pair plasma and magnetized electrons and protons: Out-of-plane magnetic field

et al. 2022

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By means of a particle-in-cell (PIC) simulation, we study the interaction between a uniform magnetized ambient electron–proton plasma at rest and an unmagnetized pair plasma, which we inject at one simulation boundary with a mildly relativistic mean speed and temperature. The magnetic field points out of the simulation plane. The injected pair plasma expels the magnetic field and piles it up at its front. It traps ambient electrons and drags them across the protons. An electric field grows, which accelerates protons into the pair cloud's expansion direction. This electromagnetic pulse separates the pair cloud from the ambient plasma. Electrons and positrons, which drift in the pulse's nonuniform field, trigger an instability that disrupts the current sheet ahead of the pulse. The wave vector of the growing perturbation is orthogonal to the magnetic field direction and magnetic tension cannot stabilize it. The electromagnetic pulse becomes permeable for pair plasma, which forms new electromagnetic pulses ahead of the initial one. A transition layer develops with a thickness of a few proton skin depths, in which protons and positrons are accelerated by strong electromagnetic fields. Protons form dense clumps surrounded by a strong magnetic field. The thickness of the transition layer grows less rapidly than we would expect from the typical speeds of the pair plasma particles and the latter transfer momentum to protons; hence, the transition layer acts as a discontinuity, separating the pair plasma from the ambient plasma. Such a discontinuity is an important building block for astrophysical pair plasma jets.

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“…Shocks in collisionless plasma, in which effects due to Coulomb collisions between charged particles are negligible compared to collective electromagnetic forces, have been studied in the laboratory [1][2][3][4][5], in the Solar system [6], and by means of numerical simulations [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Shocks are important structures for the dissipation of energy in collisionless plasma (See [16] for a recent review).…”

Section: Introductionmentioning

confidence: 99%

PIC simulations of stable surface waves on a subcritical fast magnetosonic shock front

et al. 2023

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We study with particle-in-cell (PIC) simulations the stability of fast magnetosonic shocks. They expand across a collisionless plasma and an orthogonal magnetic field that is aligned with one of the directions resolved by the 2D simulations. The shock speed is 1.6 times the fast magnetosonic speed when it enters a layer with a reduced density of mobile ions, which decreases the shock speed by up to 15\% in 1D simulations. In the 2D simulations, the density of mobile ions in the layer varies sinusoidally perpendicularly to the shock normal. We resolve one sine period. This variation only leads to small changes in the shock speed evidencing a restoring force that opposes a shock deformation. As the shock propagates through the layer, the ion density becomes increasingly spatially modulated along the shock front and the magnetic field bulges out where the mobile ion density is lowest. The perturbed shock eventually reaches a steady state. Once it leaves the layer, the perturbations of the ion density and magnetic field oscillate along its front at a frequency close to the lower-hybrid frequency; the shock is mediated by a standing wave composed of obliquely propagating lower-hybrid waves. We perform three 2D simulations with different box lengths along the shock front. The shock front oscillations are aperiodically damped in the smallest box with the fastest variation of the ion density, strongly damped in the intermediate one, and weakly damped in the largest box. The shock front oscillations perturb the magnetic field in a spatial interval that extends by several electron skin depths upstream and downstream of the shock front and could give rise to Whistler waves that propagate along the shock's magnetic field overshoot. Similar waves were observed in hybrid and PIC simulations and by the MMS satellite mission.

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Expansion of a radially symmetric blast shell into a uniformly magnetized plasma

Cited by 12 publications

References 39 publications

Steepening of Cosmic-Ray Spectra in Shocks with Varying Magnetic Field Direction

Steepening of Cosmic-Ray Spectra in Shocks with Varying Magnetic Field Direction

Two-dimensional particle simulation of the boundary between a hot pair plasma and magnetized electrons and protons: Out-of-plane magnetic field

PIC simulations of stable surface waves on a subcritical fast magnetosonic shock front

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