Polarization properties of turbulent synchrotron bubbles: an approach based on Chandrasekhar–Kendall functions

Bucciantini, N.

doi:10.1093/mnras/stx1927

Cited by 6 publications

(4 citation statements)

References 55 publications

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“…However in the low σ regime we found a strongly turbulent magnetic field structure, suggesting that perhaps a laminar model is not likely to fully capture the magnetic field, not even at the level of its average strength. For higher values of σ instead, a more coherent magnetic field is found, qualitatively in agreement with the prediction of simplified laminar models (Bucciantini 2017).…”

Section: Discussionsupporting

confidence: 87%

Full-3D relativistic MHD simulations of bow shock pulsar wind nebulae: dynamics

Olmi

Bucciantini

2019

Monthly Notices of the Royal Astronomical Society

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Bow shock pulsar wind nebulae (BSPWNe) are know to show a large variety of shapes and morphologies, both when comparing different objects, and for the same object in different energy bands. It is unclear if such a variety is related to differences in the pulsar wind properties, or to differences in the conditions of the ambient medium. We present here a set of full three-dimensional, relativistic and magneto-hydrodynamic simulations of BSPWNe, with the intention of determining how differences in the injection conditions by the pulsar wind reflect in the nebular dynamics. To achieve a good coverage of the available parameter space we have run several simulations varying those parameters that are most representative of the wind properties: the latitudinal anisotropy of the wind energy flux with respect to the pulsar spin axis, the level of magnetization, the inclination of the pulsar spin axis with respect to the pulsar direction of motion. We have followed the dynamics in these systems, not just in the very head, but also in the tail, trying to assess if and how the system retains memory of the injection at large distances from the pulsar itself. In this paper we focus our attention on the characterization of the fluid structure and magnetic field properties. We have tried to evaluate the level of turbulence in the tail, and its relation to injection, the survival of current sheets, and the degree of mixing between the shocked ambient medium and the relativistic pulsar wind material.

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Section: Discussionsupporting

confidence: 87%

Full-3D relativistic MHD simulations of bow shock pulsar wind nebulae: dynamics

Olmi

Bucciantini

2019

Monthly Notices of the Royal Astronomical Society

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“…(However, [1,2] and others had used non-Galerkin T-P methods previously, using Chebyshev polynomials instead of Bessel functions for radial dependence). C-K functions have also been used to treat astrophysical problems in a spherical geometry, rather a periodic box [16]. Again, C-K and T-P functions satisfy 'homogeneous' boundary conditions (b.c.s): the velocity and magnetic field, as well as their curls (and the curls of those, and of those, ad infinitum) all have zero normal components on the boundary.…”

Section: Historical Overviewmentioning

confidence: 99%

Inertial Waves in a Rotating Spherical Shell with Homogeneous Boundary Conditions

Shebalin

2021

Fluids

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We find the analytical form of inertial waves in an incompressible, rotating fluid constrained by concentric inner and outer spherical surfaces with homogeneous boundary conditions on the normal components of velocity and vorticity. These fields are represented by Galerkin expansions whose basis consists of toroidal and poloidal vector functions, i.e., products and curls of products of spherical Bessel functions and vector spherical harmonics. These vector basis functions also satisfy the Helmholtz equation and this has the benefit of providing each basis function with a well-defined wavenumber. Eigenmodes and associated eigenfrequencies are determined for both the ideal and dissipative cases. These eigenmodes are formed from linear combinations of the Galerkin expansion basis functions. The system is truncated to numerically study inertial wave structure, varying the number of eigenmodes. The largest system considered in detail is a 25 eigenmode system and a graphical depiction is presented of the five lowest dissipation eigenmodes, all of which are non-oscillatory. These results may be useful in understanding data produced by numerical simulations of fluid and magnetofluid turbulence in a spherical shell that use a Galerkin, toroidal–poloidal basis as well as qualitative features of liquids confined by a spherical shell.

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“…Synchrotron maps of the nebula, in the various Stoke's parameters are computed according to standard recipes (Bucciantini et The local synchrotron emissivity is integrated along the line of sight for each point of the plane of the sky. Given that radio emission is dominated by the contribution of the outer parts of the PWN, where typical flow velocity are c, one can safely neglect Doppler boosting effects (Bucciantini 2017). The local emissivity for the Stoke's parameter V describing CP is given by Legg & Westfold (1968).…”

Section: The Modelmentioning

confidence: 99%

Modeling radio circular polarization in the Crab nebula

Bucciantini

Olmi

2017

Monthly Notices of the Royal Astronomical Society

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In this paper we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extra-galactic ones. Its spectral and polarization properties allow us to infer key informations on the particles distribution function and magnetic field geometry. In recent years our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric tecniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.

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Polarization properties of turbulent synchrotron bubbles: an approach based on Chandrasekhar–Kendall functions

Cited by 6 publications

References 55 publications

Full-3D relativistic MHD simulations of bow shock pulsar wind nebulae: dynamics

Full-3D relativistic MHD simulations of bow shock pulsar wind nebulae: dynamics

Inertial Waves in a Rotating Spherical Shell with Homogeneous Boundary Conditions

Modeling radio circular polarization in the Crab nebula

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