Collisionless kinetic regimes for quasi-stationary axisymmetric accretion disc plasmas

Cremaschini, Claudio; Tessarotto, Massimo

doi:10.1063/1.4748578

Cited by 15 publications

(38 citation statements)

References 41 publications

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“…For the sake of illustration of the issue, we focus here on the relevant cases of magnetic regimes identified in Ref. 7 for plasmas belonging to the SEPE regime. First, for intermediately magnetized of type 2 plasmas the equilibrium KDF is obtained by dropping in Eq.…”

Section: Equilibrium Kdfmentioning

confidence: 99%

“…Depending on the magnitude of these parameters, several different plasma regimes can be identified, as described in Ref. 7. Following the classification scheme proposed therein, in this work for greater generality, the equilibrium plasma is assumed to belong to the strongly magnetized and strong effective potential energy (SEPE) regime for which the asymptotic orderings 0 < e M;s $ e s $ r s ( 1 ( 1 4 ) apply.…”

Section: Plasma Orderings and Regimesmentioning

confidence: 99%

“…As a basic consequence, it was shown that these equilibria can exhibit non-vanishing azimuthal and poloidal flow velocities and corresponding current densities, which can also support a kinetic dynamo mechanism for the self-generation of EM fields in which the plasma is immersed. [2][3][4][5]8,9 Remarkably, these conclusions were shown to represent ubiquitous features which in principle can characterize a variety of physical systems ranging from laboratory plasmas occurring in Tokamak devices, 1 axisymmetric accretion-disc plasmas 3,4,7 and current-carrying magnetic loops 9 around compact objects as well as spatially non-symmetric systems in astrophysical and laboratory contexts. 2 In this reference, it must be pointed out, however, that in principle this kind of kinetic dynamo can also operate in combination with other alternative generation effects of different nature (see, for example, Refs.…”

Section: Introductionmentioning

confidence: 98%

“…The investigation is based on a kinetic theory and is developed in the framework of the Vlasov-Maxwell description appropriate for the treatment of non-relativistic systems in quasi-stationary configurations. The work is part of an investigation concerning the formulation of kinetic theory for magnetized plasmas in laboratory devices 1,2 and astrophysical scenarios of equilibrium plasmas arising around compact objects, [2][3][4][5][6][7][8][9] and its application to the study of their phenomenology, including their stability properties. 10 It is known that the kinetic treatment provides the appropriate description of collisionless plasmas for which both phase-space single-particle dynamics as well as phase-space collective phenomena must be taken into account.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic theory of quasi-stationary collisionless axisymmetric plasmas in the presence of strong rotation phenomena

2013

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The problem of formulating a kinetic treatment for quasi-stationary collisionless plasmas in axisymmetric systems subject to the possibly independent presence of local strong velocity-shear and supersonic rotation velocities is posed. The theory is developed in the framework of the Vlasov-Maxwell description for multi-species non-relativistic plasmas. Applications to astrophysical accretion discs arising around compact objects and to plasmas in laboratory devices are considered. Explicit solutions for the equilibrium kinetic distribution function (KDF) are constructed based on the identification of the relevant particle adiabatic invariants. These are shown to be expressed in terms of generalized non-isotropic Gaussian distributions. A suitable perturbative theory is then developed which allows for the treatment of non-uniform strong velocity-shear/supersonic plasmas. This yields a series representation for the equilibrium KDF in which the leading-order term depends on both a finite set of fluid fields as well as on the gradients of an appropriate rotational frequency. Constitutive equations for the fluid number density, flow velocity, and pressure tensor are explicitly calculated. As a notable outcome, the discovery of a new mechanism for generating temperature and pressure anisotropies is pointed out, which represents a characteristic feature of plasmas considered here. This is shown to arise as a consequence of the canonical momentum conservation and to contribute to the occurrence of temperature anisotropy in combination with the adiabatic conservation of the particle magnetic moment. The physical relevance of the result and the implications of the kinetic solution for the self-generation of quasi-stationary electrostatic and magnetic fields through a kinetic dynamo are discussed. V C 2013 AIP Publishing LLC. [http://dx.

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Section: Equilibrium Kdfmentioning

confidence: 99%

Section: Plasma Orderings and Regimesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetic theory of quasi-stationary collisionless axisymmetric plasmas in the presence of strong rotation phenomena

2013

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“…2 This in turn requires the identification of the regimes that characterize the plasma states, which are determined by the plasma microscopic and macroscopic properties. 3 Two types of processes should be distinguished in this regard: the first one concerns particle dynamics, while the second one deals with collective phenomena in plasmas. In particular, the first category includes a variety of EM interactions/processes ranging from particle binary Coulomb collisions, singleparticle radiation emission (radiation-reaction), 4-11 chemical or nuclear processes as well as the influence of intense electromagnetic fields on single particle dynamics (gyrokinetic (GK) theory).…”

Section: Introductionmentioning

confidence: 99%

Covariant formulation of spatially non-symmetric kinetic equilibria in magnetized astrophysical plasmas

2014

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Astrophysical plasmas in the surrounding of compact objects and subject to intense gravitational and electromagnetic fields are believed to give rise to relativistic regimes. Theoretical and observational evidences suggest that magnetized plasmas of this type are collisionless and can persist for long times (e.g., with respect to a distant observer, coordinate, time), while exhibiting geometrical structures characterized by the absence of well-defined spatial symmetries. In this paper, the problem is posed whether such configurations can correspond to some kind of kinetic equilibrium. The issue is addressed from a theoretical perspective in the framework of a covariant Vlasov statistical description, which relies on the method of invariants. For this purpose, a systematic covariant variational formulation of gyrokinetic theory is developed, which holds without requiring any symmetry condition on the background fields. As a result, an asymptotic representation of the relativistic particle magnetic moment is obtained from its formal exact solution, in terms of a suitably defined invariant series expansion parameter (perturbative representation). On such a basis, it is shown that spatially non-symmetric kinetic equilibria can actually be determined, an example being provided by Gaussian-like distributions. As an application, the physical mechanisms related to the occurrence of a non-vanishing equilibrium fluid 4-flow are investigated. V C 2014 AIP Publishing LLC. [http://dx.

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Asymptotic orderings and approximations of the Master kinetic equation for large hard spheres systems

Tessarotto

Asci

2017

Physics Letters A

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In this paper the problem is posed of determining the physically-meaningful asymptotic orderings holding for the statistical description of a large N −body system of hard spheres, i.e., formed by N ≡ 1 ε ≫ 1 particles, which are allowed to undergo instantaneous and purely elastic unary, binary or multiple collisions. Starting point is the axiomatic treatment recently developed [Tessarotto et al., 2013 and the related discovery of an exact kinetic equation realized by Master equation which advances in time the 1−body probability density function (PDF) for such a system. As shown in the paper the task involves introducing appropriate asymptotic orderings in terms of ε for all the physically-relevant parameters. The goal is that of identifying the relevant physically-meaningful asymptotic approximations applicable for the Master kinetic equation, together with their possible relationships with the Boltzmann and Enskog kinetic equations, and holding in appropriate asymptotic regimes. These correspond either to dilute or dense systems and are formed either by small-size or finite-size identical hard spheres, the distinction between the various cases depending on suitable asymptotic orderings in terms of ε. -INTRODUCTIONIn a series of papers [1][2][3][4][5][6][7] (see also Refs. [8,9]) a new kinetic equation has been established for hard sphere systems subject to elastic instantaneous collisions, denoted as Master kinetic equation. Its basic features are that, unlike the Boltzmann and Enskog kinetic equations [11][12][13], the same equation and its corresponding Master collision operator are exact, i.e., they hold for an arbitraryN −body hard-sphere system S N which is isolated, namely for which the number of particles (N ) is constant, while furthermore that its solutions are entropy-preserving [6] and globally defined [7]. Concerning, in particular, the first feature this means that in such a context S N is allowed to have an arbitrary finite number N of finite-size and finite-mass hard spheres, namely each one characterized by finite diameter σ > 0 and mass m > 0. In addition, by assumption S N is immersed in a bounded configuration domain Ω, subset of the Euclidean space R 3 which has a finite canonical measure L 3 o ≡ µ(Ω) > 0 (L o denoting a finite configuration-domain characteristic scale length) and is endowed with a stationary and rigid boundary ∂Ω. However, the total volume occupied by hard-spheres cannot exceed the configuration-space volume. Hence, the parameters N, L o and σ must necessarily satisfy the inequalitydenoting the volume of a single hard sphere and ∆ the global diluteness parameter. For such an equation the particle correlations appearing through the 2−body probability density function (PDF) are exactly taken into account by means of suitably-prescribed 1− and 2−body occupation coefficients which are position-dependent only. These peculiar features follow uniquely as a consequence of the new approach to classical statistical mechanics developed in Refs. [1][2][3] and referred to as "ab initio...

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Collisionless kinetic regimes for quasi-stationary axisymmetric accretion disc plasmas

Cited by 15 publications

References 41 publications

Kinetic theory of quasi-stationary collisionless axisymmetric plasmas in the presence of strong rotation phenomena

Kinetic theory of quasi-stationary collisionless axisymmetric plasmas in the presence of strong rotation phenomena

Covariant formulation of spatially non-symmetric kinetic equilibria in magnetized astrophysical plasmas

Asymptotic orderings and approximations of the Master kinetic equation for large hard spheres systems

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