Kinetic description of quasi-stationary axisymmetric collisionless accretion disk plasmas with arbitrary magnetic field configurations
- International School for Advanced Studies (SISSA), Trieste 34136 (Italy)
- International School for Advanced Studies (SISSA) and INFN, Trieste 34136, Italy and Department of Physics (Astrophysics), University of Oxford, Oxford OX1 3RH (United Kingdom)
- Department of Mathematics and Informatics, University of Trieste, Trieste 34127 (Italy)
A kinetic treatment is developed for collisionless magnetized plasmas occurring in high-temperature, 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 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'' are discussed. Both effects are shown to be related to intrinsically kinetic physical mechanisms.
- OSTI ID:
- 21546963
- Journal Information:
- Physics of Plasmas, Vol. 18, Issue 6; Other Information: DOI: 10.1063/1.3592674; (c) 2011 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACCRETION DISKS
ASYMPTOTIC SOLUTIONS
AXIAL SYMMETRY
BOLTZMANN-VLASOV EQUATION
CHARGED-PARTICLE TRANSPORT
COLLISIONLESS PLASMA
DISTRIBUTION FUNCTIONS
MAGNETIC FIELDS
MAGNETIC SURFACES
PLASMA CONFINEMENT
CONFINEMENT
DIFFERENTIAL EQUATIONS
EQUATIONS
FUNCTIONS
MAGNETIC FIELD CONFIGURATIONS
MATHEMATICAL SOLUTIONS
PARTIAL DIFFERENTIAL EQUATIONS
PLASMA
RADIATION TRANSPORT
SYMMETRY