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1. Preflight Prediction and Optimization of a Reduced Gravity Experiment to Investigate Magnetic Positive Positioning of LOX

Author

Aiaa Paper, Amanda P. Winter, and Jeffrey G. Marchetta

Subjects
Electromagnetic field, Propellant, Engineering, business.industry, Design of experiments, Mechanical engineering, Mechanics, Magnetic field, Physics::Fluid Dynamics, Acceleration, Magnet, Fluid dynamics, Compressibility, business
Abstract

Simulation of magnetic positive positioning of propellants (MP 3 ) in full-scale applications depends on the ability to model the shape and strength of the magnetic fields required to induce fluid flow. A previous effort to integrate an electromagnetic field and incompressible fluid flow model yielded a unique tool that can be used to predict fluid motion induced by a magnetic field. The enhanced computational simulation is used to predict an optimal configuration for an upcoming flight experiment focused on studying the influence of a magnetic field on LOX in reduced gravity. Simulations of magnetic positive positioning of LOX are presented and the influence of the magnetic field and background acceleration on the settling time is investigated to determine an appropriate tank and liquid configuration to induce successful reorientation during the flight experiment. Variations in the magnet thickness, LOX tank size, background acceleration, and LOX tank fill are considered to predict the optimal experiment design. The magnetic Bond number and a dimensionless reorientation time are utilized as correlating parameters for this study and may be useful in future efforts to relate magnetically induced flows for small-scale experiments to the behavior of propellants in full-size systems.

Published
2005

2. Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer

Author

M. González, Benoît Commerçon, R. Mignon-Risse, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), This work was supported by the CNRS 'Programme National de Physique Stellaire' (PNPS), The numerical simulations we have presented in this paper were produced on the CEA machine Alfvén and using HPC resources from GENCI-CINES (Grant A0080407247). The visualisation of RAMSES data has been done with the OSYRIS python package., Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Bordeaux Sciences Agro [Gradignan], and Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)

Subjects
Magnetohydrodynamics (MHD), Astrophysics::High Energy Astrophysical Phenomena, Stars: formation, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Stars: protostars, Acceleration, 0103 physical sciences, Radiative transfer, Protostar, Astrophysics::Solar and Stellar Astrophysics, Stars: massive, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Methods: numerical, 010308 nuclear & particles physics, Turbulence, Ambipolar diffusion, Velocity dispersion, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics - Astrophysics of Galaxies, Magnetic field, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Outflow, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

(Abridged) Most massive protostars exhibit bipolar outflows. Nonetheless, there is no consensus regarding the mechanism at the origin of these outflows, nor on the cause of the less-frequently observed monopolar outflows. We aim to identify the origin of early massive protostellar outflows, focusing on the combined effects of radiative transfer and magnetic fields in a turbulent medium. We use four state-of-the-art radiation-magnetohydrodynamical simulations following the collapse of massive 100 Msun pre-stellar cores with the Ramses code. Turbulence is taken into account via initial velocity dispersion. We use a hybrid radiative transfer method and include ambipolar diffusion. We find that turbulence delays the launching of outflows, which appear to be mainly driven by magnetohydrodynamical processes. Magnetic tower flow and the magneto-centrifugal acceleration contribute to the acceleration and the former operates on larger volumes than the latter. Our finest resolution, 5 AU, does not allow us to get converged results on magneto-centrifugally accelerated outflows. Radiative acceleration takes place as well, dominates in the star vicinity, enlarges the outflow extent, and has no negative impact on the launching of magnetic outflows (up to M~17 Msun, L~1e5 Lsun). The associated opening angles (20-30 deg when magnetic fields dominate) suggest additional (de-)collimating effects to meet observational constraints. Outflows are launched nearly perpendicular to the disk and are misaligned with the initial core-scale magnetic fields, in agreement with several observational studies. In the most turbulent run, the outflow is monopolar. We conclude that magnetic processes dominate the acceleration of massive protostellar outflows up to ~17 Msun, against radiative processes. Turbulence perturbs the outflow launching and is a possible explanation for monopolar outflows., Accepted for publication in A&A, 20 pages, 15 figures

Published
2021

3. Chiral sound waves in strained Weyl semimetals

Author

María A. H. Vozmediano, M. N. Chernodub, Institut Denis Poisson (IDP), Centre National de la Recherche Scientifique (CNRS)-Université de Tours (UT)-Université d'Orléans (UO), Laboratory of Physics of Living Matter [Vladivostok], School of Biomedicine [Vladivostok], Far Eastern Federal University (FEFU)-Far Eastern Federal University (FEFU), Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), This paper was partially supported by Spanish MECD grant FIS2014-57432-P, the Comunidad de Madrid MAD2D-CM Program (S2013/MIT-3007),Grant 3.6261.2017/8.9 of the Ministry of Science and Higher Education of Russia, and Spanish-French mobility project PIC2016FR6/PICS07480., and Centre National de la Recherche Scientifique (CNRS)-Université de Tours-Université d'Orléans (UO)

Subjects
Chiral anomaly, Physics, High Energy Physics - Theory, Field (physics), Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, High Energy Physics::Lattice, High Energy Physics::Phenomenology, Charge density, Weyl semimetal, FOS: Physical sciences, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Magnetic field, High Energy Physics - Theory (hep-th), [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], 010306 general physics, 0210 nano-technology, Charge density wave, Plasmon, Excitation
Abstract

We show that a strained wire of a Weyl semimetal supports a new type of gapless excitation, the chiral sound wave (CSW). It is a longitudinal charge density wave analog to the chiral magnetic wave predicted in the quark-gluon plasma but driven by an elastic axial pseudo-magnetic field. It involves the axial-axial-axial contribution to the chiral anomaly which couples the chiral charge density to the elastic axial gauge field. The chiral sound is unidirectional: it propagates along the elastic magnetic field and not in the opposite direction. The CSW may propagate for long distances as it does not couple directly to quickly dissipating electromagnetic plasmons, while its damping is controlled by the slow chirality flip rate. We propose an experimental setup to directly detect the chiral sound, which is excited by mechanical vibrations of the crystal lattice in the GHz frequency range. Our findings contribute to a new trend, the chiral acoustics, in strained Weyl semimetals., Comment: 5 pages, 3 figures; v2: minor changes, published version

Published
2019

4. 3D Modeling of Coils for Pulsed Field Magnetization of HTS Bulk Pellets in an Electrical Machine

Author

Mariusz Stepien, Alexandre Colle, Kévin Berger, Thierry Lubin, Boguslaw Grzesik, Jean Lévêque, Jakub Kapek, Groupe de Recherche en Energie Electrique de Nancy (GREEN), Université de Lorraine (UL), Department of Power Electronics, Electrical Drives and Robotics, Silesian University of Technology, The authors would like to acknowledge the 'Région Lorraine' for its financial support concerning the purchase of the pulsed current source. Jakub Kapek would like to thanks the Erasmus+ program for the funding of his internship in Nancy., and The authors would like to thank Rachid Dadi from VACUUMSCHMELZE GmbH for providing us with the VACODUR 50 material, and Salah Eddine Bentridi for the English proofreading of the final version of the paper.

Subjects
Cryostat, Transient state, Materials science, Inductor, 01 natural sciences, Magnetization, 0103 physical sciences, Electrical and Electronic Engineering, 010306 general physics, Inductance, Pulse measurements, 010302 applied physics, Superconductivity, Condensed matter physics, [SPI.NRJ]Engineering Sciences [physics]/Electric power, Modeling, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Magnetic field, Superconducting rotating machines, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Very high field and NMR magnets, [SPI.ELEC]Engineering Sciences [physics]/Electromagnetism, Electromagnetic coil, Bulk conductors
Abstract

International audience; In this work, we propose to study and design a coil used to magnetize, by means of a Pulsed Field Magnetization (PFM) process, an inductor of a radial flux superconducting machine with one pair of poles. Each pole contains four similar HTS bulks of 30 mm diameter arranged in a square pattern. The cryostat already exists for this application and the temperature of the HTS bulks can vary from 4.2 K to their critical temperature, in transient state. For a given primary source of energy, here a capacitor bank of 10 kJ (5 mF, 2 kV) is available, the PFM process depends strongly on the value of the coil inductance used to generate pulsed field, because it defines the waveform of the current: peak value and time constant. Thus, 3D modeling of the coil is required in order to be sure that its inductance and the magnetic field produced will provide a full magnetization of HTS bulks. From the practical point of view, we would like to achieve an average magnetization of each pole around 3 T. In this paper, numerical modeling of coils with different number of turns coupled with circuit's equations is achieved. The maximum magnetic field obtained on the HTS bulks and estimated magnetization at the top center of each HTS bulk, are presented and discussed.

Published
2018

5. Angular momentum transport and large eddy simulations in magnetorotational turbulence: the small Pm limit

Author

Pierre-Yves Longaretti, S. Fromang, Geoffroy Lesur, Heloise Meheut, M. Joos, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), The simulations presented in this paper were granted access to the HPC resources of CCRT under the allocation x2012042231 made by GENCI (Grand Équipement National de Calcul Intensif), European Project: 258729,EC:FP7:ERC,ERC-2010-StG_20091028,PETADISK(2011), European Project: 294110,EC:FP7:PEOPLE,FP7-PEOPLE-2011-CIG,HALLDISCS(2012), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Angular momentum, FOS: Physical sciences, Astrophysics, Magnetohydrodynamic turbulence, 01 natural sciences, magnetohydrodynamics (MHD), methods: numerical, accretion, Magnetorotational instability, 0103 physical sciences, Magnetic pressure, Magnetic Prandtl number, 010306 general physics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Earth and Planetary Astrophysics (astro-ph.EP), Physics, Turbulence, accretion disks, turbulence, protoplanetary disks, Fluid Dynamics (physics.flu-dyn), Astronomy and Astrophysics, Physics - Fluid Dynamics, Computational physics, Magnetic field, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract

Angular momentum transport in accretion discs is often believed to be due to magnetohydrodynamic turbulence mediated by the magnetorotational instability. Despite an abundant literature on the MRI, the parameters governing the saturation amplitude of the turbulence are poorly understood and the existence of an asymptotic behavior in the Ohmic diffusion regime is not clearly established. We investigate the properties of the turbulent state in the small magnetic Prandtl number limit. Since this is extremely computationally expensive, we also study the relevance and range of applicability of the most common subgrid scale models for this problem. Unstratified shearing boxes simulations are performed both in the compressible and incompressible limits, with a resolution up to 800 cells per disc scale height. The latter constitutes the largest resolution ever attained for a simulation of MRI turbulence. In the presence of a mean magnetic field threading the domain, angular momentum transport converges to a finite value in the small Pm limit. When the mean vertical field amplitude is such that {\beta}, the ratio between the thermal and magnetic pressure, equals 1000, we find {\alpha}~0.032 when Pm approaches zero. In the case of a mean toroidal field for which {\beta}=100, we find {\alpha}~0.018 in the same limit. Both implicit LES and Chollet-Lesieur closure model reproduces these results for the {\alpha} parameter and the power spectra. A reduction in computational cost of a factor at least 16 (and up to 256) is achieved when using such methods. MRI turbulence operates efficiently in the small Pm limit provided there is a mean magnetic field. Implicit LES offers a practical and efficient mean of investigation of this regime but should be used with care, particularly in the case of a vertical field. Chollet-Lesieur closure model is perfectly suited for simulations done with a spectral code., Comment: Accepted for publication in A&A

Published
2015

6. Thanatology in protoplanetary discs - The combined influence of Ohmic, Hall, and ambipolar diffusion on dead zones

Author

Geoffroy Lesur, Sebastien Fromang, Matthew W. Kunz, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Department of Astrophysical Sciences [Princeton], Princeton University, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Support for G.L. was provided by the European Community via contract PCIG09-GA-2011-294110. Support for M.W.K. was provided by NASA through Einstein Postdoctoral Fellowship Award Number PF1-120084, issued by theChandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. Support for S.F. was provided by the European Research Council under the European Union’s Seventh Framework Programme(FP7/2007-2013)/ERC Grant agreement n 258729. Most of the the computa-tions presented in this paper were performed using the Froggy platform of theCIMENT infrastructure (https://ciment.ujf-grenoble.fr), which is supported bythe Rhône-Alpes region (GRANT CPER07_13 CIRA), the OSUG@2020 labex(reference ANR10 LABX56) and the Equip@Meso project (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervised by theAgence Nationale pour la Recherche. This work was granted access to the HPCresources of IDRIS under allocation x2014042231 made by GENCI (GrandEquipement National de Calcul Intensif), European Project: 258729,EC:FP7:ERC,ERC-2010-StG_20091028,PETADISK(2011), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112))

Subjects
010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astrophysics, 01 natural sciences, magnetohydrodynamics (MHD), accretion, Hall effect, Magnetorotational instability, 0103 physical sciences, Magnetic pressure, Diffusion (business), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), stars: formation, Accretion (meteorology), Ambipolar diffusion, accretion disks, protoplanetary disks, Astronomy and Astrophysics, Mechanics, Magnetic field, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, instabilities, Astrophysics::Earth and Planetary Astrophysics, Magnetohydrodynamics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract

Protoplanetary discs are poorly ionised due to their low temperatures and high column densities, and are therefore subject to three "non-ideal" magnetohydrodynamic effects: Ohmic dissipation, ambipolar diffusion, and the Hall effect. The existence of magnetically driven turbulence in these discs has been a central question since the discovery of the magnetorotational instability. Early models considered Ohmic diffusion only and led to a scenario of layered accretion, in which a magnetically "dead" zone in the disc midplane is embedded within magnetically "active" surface layers at distances ~1-10 au from the central protostellar object. Recent work has suggested that a combination of Ohmic dissipation and ambipolar diffusion can render both the midplane and surface layers of the disc inactive and that torques due to magnetically driven outflows are required to explain the observed accretion rates. We reassess this picture by performing three-dimensional numerical simulations that include, for the first time, all three non-ideal MHD effects. We find that the Hall effect can generically "revive" dead zones by producing a dominant azimuthal magnetic field and a large-scale Maxwell stress throughout the midplane, provided the angular velocity and magnetic field satisfy Omega.B > 0. The attendant large magnetic pressure modifies the vertical density profile and substantially increases the disc scale height beyond its hydrostatic value. Outflows are produced, but are not necessary to explain accretion rates, 16 pages, 18 figures, 3 tables, accepted for publication in Astronomy & Astrophysics

Published
2014

7. Kinetic theory of plasmas

Author

Thierry Magin, Marc Massot, Benjamin Graille, Center for Turbulence Research [Stanford] (CTR), Stanford University, Laboratoire de Mathématiques d'Orsay (LM-Orsay), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion (EM2C), Université Paris Saclay (COmUE)-Centre National de la Recherche Scientifique (CNRS)-CentraleSupélec, Papers presented during the AVT-162 RTO AVT/VKI Lecture Series held at the von Karman Institute, Rhode St. Genèse, Belgium., CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université Paris Saclay (COmUE), and The authors acknowledge support from two scientific departments of CNRS (French Center for Scientific Research): MPPU (Mathématiques, Physique, Planète et Univers) and ST2I (Sciences et Technologies de l'Information et de l'Ingénierie), through a 2007-2008 PEPS project entitled: ``Analyse et simulation de problèmes multi-échelles : applications aux plasmas froids, à la combustion et aux écoulements diphasiques'.

Subjects
Electromagnetic field, Physics, plasmas in thermal nonequilibrium, Internal energy, 82C40, 76X05, 41A60, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, [SPI.PLASMA]Engineering Sciences [physics]/Plasmas, Non-equilibrium thermodynamics, Electron, 01 natural sciences, Boltzmann equation, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], 010305 fluids & plasmas, Magnetic field, Classical mechanics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, [MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP], conservation equations, multicomponent transport properties, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], Kinetic theory, 010306 general physics, Boltzmann's entropy formula, Scaling
Abstract

International audience; In the present study, we derive from kinetic theory a unified fluid model for multi- component plasmas by accounting for the electromagnetic field influence. We deal with a possible thermal nonequilibrium of the translational energy of the particles, neglecting their internal energy and reactive collisions. Given the strong disparity of mass between the electrons and heavy particles, such as molecules, atoms, and ions, we conduct a dimen- sional analysis of the Boltzmann equation and introduce a scaling based on a multiscale perturbation parameter equal to the square root of the ratio of the electron mass to a characteristic heavy-particle mass. We then generalize the Chapman-Enskog method, em- phasizing the role of the perturbation parameter on the collisional operator, the streaming operator, and the collisional invariants of the Boltzmann equation. The system is exam- ined at successive orders of approximation, each corresponding to a physical time scale. At the highest approximation order investigated, the multicomponent Navier-Stokes regime is reached for the heavy particles and is coupled to first-order drift-diffusion equations for the electrons. The transport coefficients are then calculated in terms of bracket opera- tors whose mathematical structure allows for positivity properties to be determined and Onsager's reciprocal relations to hold. The transport coefficients exhibit an anisotropic behavior when the magnetic field is strong enough. We also give a complete description of the Kolesnikov effect, i.e., the crossed contributions to the mass and energy transport fluxes coupling the electrons and heavy particles. Finally, the first and second laws of ther- modynamics are proved to be satisfied by deriving a total energy equation and an entropy equation.