Axi-symmetric Gravitational MHD Equilibria in the Presence of Plasma Rotation

Cremaschini, Claudio; Beklemishev, A. D.; Miller, John C.; Tessarotto, Massimo

doi:10.1063/1.3076441

Cited by 6 publications

(12 citation statements)

References 8 publications

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“…Requirements 1) -7) clearly imply that the solution cannot generally be a Maxwellian. However, in analogy with Paper I, it is possible to show that they can be fulfilled by a suitable modified bi-Maxwellian expressed solely in terms of first integrals of motion and adiabatic invariants [6,10,39]. It follows that this is necessarily a QSA-KDF.…”

Section: Construction Of the Qsa-kdf: Generalized Solutionmentioning

confidence: 77%

“…The origin of their magnetic fields varies depending on the type of the central object: in the case of black holes, the fields are only ones self-generated by currents in the plasma itself via dynamo effects, while with neutron stars and white dwarfs there can also be a magnetic field intrinsic to the central object [1,2]. The interplay between magnetic fields and accretion plasmas can affect the overall velocity profile of the disk, as well as giving rise to species-dependent velocities and rotational frequencies [4,5,10]. Moreover, the magnetic field can be a source of anisotropies in the KDF and allow particular symmetries which influence both the single particle and collective plasma behavior.…”

Section: A Accretion Disks In Astrophysicsmentioning

confidence: 99%

“…In contrast with the majority of previous treatments, which are based on fluid approaches within the context of hydrodynamics (HD) or magnetohydrodynamics (MHD) [1][2][3][4][5], here we adopt a kinetic approach. This provides a phase-space treatment allowing us to formulate a consistent description of plasma dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…[6]) and kinetic trapping phenomena. These properties are relevant for magnetized plasmas and in particular for those arising in ADs [7][8][9] whenever the plasma is regarded as collisionless or weakly collisional [6,10].…”

Section: Introductionmentioning

confidence: 99%

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Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations

Cremaschini¹,

Miller²,

Tessarotto³

2011

Physics of Plasmas

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A kinetic treatment is developed for collisionless magnetized plasmas occurring in hightemperature, low-density astrophysical accretion disks, such as are thought to be present in some radiatively-inefficient accretion flows onto black holes. Quasi-stationary configurations are investigated, within the framework of a Vlasov-Maxwell description. The plasma is taken to be axisymmetric and subject to the action of slowly time-varying gravitational and electromagnetic fields. The magnetic field is assumed to be characterized by a family of locally nested but open magnetic surfaces. The slow collisionless dynamics of these plasmas is investigated, yielding a reduced gyrokinetic Vlasov equation for the kinetic distribution function. For doing this, an asymptotic quasi-stationary solution is first determined, represented by a generalized bi-Maxwellian distribution expressed in terms of the relevant adiabatic invariants. The existence of the solution is shown to depend on having suitable kinetic constraints and conditions leading to particle trapping phenomena. With this solution one can treat temperature anisotropy, toroidal and poloidal flow velocities and finite Larmor-radius effects. An asymptotic expansion for the distribution function permits analytic evaluation of all of the relevant fluid fields. Basic theoretical features of the solution and their astrophysical implications are discussed. As an application, the possibility of describing the dynamics of slowly time-varying accretion flows and the self-generation of magnetic field by means of a "kinetic dynamo effect" is discussed. Both effects are shown to be related to intrinsically-kinetic physical mechanisms.

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Section: Construction Of the Qsa-kdf: Generalized Solutionmentioning

confidence: 77%

Section: A Accretion Disks In Astrophysicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations

Cremaschini¹,

Miller²,

Tessarotto³

2011

Physics of Plasmas

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“…• The treatment of the gravitational field produced by the central massive object is handled by the introduction of a pseudo-Newtonian potential G ef f [7]. This allows us to take into account relativistic corrections carried by the local space-time curvature.…”

Section: Introduction and Motivationsmentioning

confidence: 99%

Generalized Grad-Shafranov Equation for Gravitational Hall-MHD Equilibria

Cremaschini¹,

Beklemishev²,

Miller³

et al. 2008

AIP Conference Proceedings

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The consistent theoretical description of gravitational Hall-MHD (G-Hall-MHD) equilibria is of fundamental importance for understanding the phenomenology of accretion disks (AD) around compact objects (black holes, neutron stars, etc.). The very existence of these equilibria is actually suggested by observations, which show evidence of quiescent, and essentially non-relativistic, AD plasmas close to compact stars, thus indicating that accretion disks may be characterized by slowly varying EM and fluid fields. These (EM) fields, in particular the electric field, may locally be extremely intense, so that AD plasmas are likely to be locally non-neutral and therefore characterized by the presence of Hall currents. This suggests therefore that such equilibria should be described in the framework of the Hall-MHD theory. Extending previous approaches, holding for non-rotating plasmas or based on specialized single-species model equilibria which ignore the effect of space-time curvature, the purpose of this work is the formulation of a generalized Grad-Shafranov (GGS) equation suitable for the investigation of G-Hall-MHD equilibria in AD's where non-relativistic plasmas are present. For this purpose the equilibria are assumed to be generated by a strong axisymmetric stellar magnetic field and by the gravitating plasma characterizing the AD.PACS numbers: 95.30.Qd,97.10.Gz

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Theory of quasi-stationary kinetic dynamos in magnetized accretion discs

2010

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Abstract. Magnetic fields are a distinctive feature of accretion disc plasmas around compact objects (i.e., black holes and neutron stars) and they play a decisive role in their dynamical evolution. A fundamental theoretical question related with this concerns investigation of the socalled gravitational MHD dynamo effect, responsible for the self-generation of magnetic fields in these systems. Experimental observations and theoretical models, based on fluid MHD descriptions of various types support the conjecture that accretion discs should be characterized by coherent and slowly time-varying magnetic fields with both poloidal and toroidal components. However, the precise origin of these magnetic structures and their interaction with the disc plasmas is currently unclear. The aim of this paper is to address this problem in the context of kinetic theory. The starting point is the investigation of a general class of Vlasov-Maxwell kinetic equilibria for axi-symmetric collisionless magnetized plasmas characterized by temperature anisotropy and mainly toroidal flow velocity. Retaining finite Larmor-radius effects in the calculation of the fluid fields, we show how these configurations are capable of sustaining both toroidal and poloidal current densities. As a result, we suggest the possible existence of a kinetic dynamo effect, which can generate a stationary toroidal magnetic field in the disc even without any net radial accretion flow. The results presented may have important implications for equilibrium solutions and stability analysis of accretion disc dynamics.

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Axi-symmetric Gravitational MHD Equilibria in the Presence of Plasma Rotation

Cited by 6 publications

References 8 publications

Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations

Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations

Generalized Grad-Shafranov Equation for Gravitational Hall-MHD Equilibria

Theory of quasi-stationary kinetic dynamos in magnetized accretion discs

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