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In dilute astrophysical plasmas, the collisional mean free path of a particle can exceed its Larmor radius. Under these conditions, the thermal conductivity and viscosity of the plasma can be dramatically altered. This alteration allows…

天体物理学 · 物理学 2009-11-11 Tanim Islam , Steven Balbus

By performing a global magneto-hydrodynamical simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion…

星系天体物理 · 物理学 2015-10-28 Takeru K. Suzuki , Yasuo Fukui , Kazufumi Torii , Mami Machida , Ryoji Matsumoto

We present an axisymmetric numerical model of a dynamo active accretion disc. If the dynamo-generated magnetic field in the disc is sufficiently strong (close to equipartition with thermal energy), a fast magneto-centrifugally driven…

天体物理学 · 物理学 2009-10-31 Brigitta von Rekowski , Axel Brandenburg , Wolfgang Dobler , Anvar Shukurov

Observations in polarized emission reveal the existence of large-scale coherent magnetic fields in a wide range of spiral galaxies. Radio-polarization data show that these fields are strongly inclined towards the radial direction, with…

天体物理学 · 物理学 2009-11-13 Oliver Gressel , Udo Ziegler , Detlef Elstner , Günther Rüdiger

We examine the behaviour of an axisymmetric galactic dynamo model with a radial accretion flow in the disc. We also introduce a vertical magnetic flux through the galactic midplane, to simulate the presence of a large scale magnetic field…

天体物理学 · 物理学 2009-10-31 David Moss , Anvar Shukurov

We analyze an axisymmetric magnetohydrodynamics configuration, describing the morphology of a purely differentially rotating thin plasma disk, in which linear and non-linear perturbations are triggered associated with microscopic magnetic…

太阳与恒星天体物理 · 物理学 2018-10-02 Giovanni Montani , Mariachiara Rizzo , Nakia Carlevaro

We performed 2D and full 3D magnetohydrodynamic simulations of disk accretion to a rotating star with an aligned or misaligned dipole magnetic field. We investigated the rotational equilibrium state and derived from simulations the ratio…

天体物理学 · 物理学 2009-11-11 M. M. Romanova , A. K. Kulkarni , M. Long , R. V. E. Lovelace , J. V. Wick , G. V. Ustyugova , A. V. Koldoba

This study investigates Parker instability in an interstellar medium (ISM) near the Galactic plane using three-dimensional magneto-hydrodynamic simulations. Parker instability arises from the presence of a magnetic field in a plasma,…

高能天体物理现象 · 物理学 2011-01-06 Ying-Yi Lo , Chung-Ming Ko , Chih-Yueh Wang

Dynamos in astrophysical disks are usually explained in terms of the standard alpha-omega mean field dynamo model where the local helicity generates a radial field component from an azimuthal field. The subsequent shearing of the radial…

天体物理学 · 物理学 2015-06-24 Ethan T. Vishniac

The kinematic evolution of axisymmetric magnetic fields in rotating magnetospheres of relativistic compact objects is analytically studied, based on relativistic Ohm's law in stationary axisymmetric geometry. By neglecting the poloidal…

天体物理学 · 物理学 2009-10-31 Akira Tomimatsu

Magnetic fields are known to be dynamically important in the interstellar medium of our own Galaxy, and they are ubiquitously observed in diffuse gas in the halos of galaxies and galaxy clusters. Yet, magnetic fields have typically been…

宇宙学与河外天体物理 · 物理学 2014-03-05 R. Pakmor , V. Springel

A linear stability analysis of a multi-component and magnetized Galactic disk model is presented. The disk model uses the observed stratifications for the gas density and gravitational acceleration at the solar neighborhood and, in this…

天体物理学 · 物理学 2009-10-31 Jongsoo Kim , Jose Franco , S. S. Hong , Alfredo Santillan , Marco A. Martos

When the ion mean free path much exceeds the Larmor radius in a plasma, the viscous stress tensor is altered dramatically, and depends only upon quantities measured along the field lines. This regime corresponds to typical interstellar…

天体物理学 · 物理学 2009-11-10 Steven A. Balbus

The magneto-rotational instability (MRI) is the most likely mechanism for transportation of angular momentum and dissipation of energy within hot, ionized accretion discs. This instability is produced through the interactions of a…

高能天体物理现象 · 物理学 2021-12-08 Oscar M. Pimentel , P. Chris Fragile , F. D. Lora-Clavijo , Bridget Ierace , Deepika Bollimpalli

The structure and evolution of protoplanetary disks (PPDs) are largely governed by disk angular momentum transport, mediated by magnetic fields. In the most observable outer disk, PPD gas dynamics is primarily controlled by ambipolar…

地球与行星天体物理 · 物理学 2021-08-11 Can Cui , Xue-Ning Bai

Spiral galaxies host dynamically important magnetic fields which can affect gas flows in the disks and halos. Total magnetic fields in spiral galaxies are strongest (up to 30 \muG) in the spiral arms where they are mostly turbulent or…

天体物理学 · 物理学 2009-06-23 Rainer Beck

By performing a global magnetohydrodynamical (MHD) simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular…

星系天体物理 · 物理学 2017-02-22 Takeru K. Suzuki , Yasuo Fukui , Kazufumi Torii , Mami Machida , Ryoji Matsumoto , Kensuke Kakiuchi

The evolution of large-scale magnetic fields in disk galaxies is investigated numerically. The gasdynamical simulations in a disk perturbed by spiral or bar potential are incorporated into the kinematic calculations of induction equations…

天体物理学 · 物理学 2007-05-23 K. Otmianowska-Mazur , M. Chiba

We have investigated evolution of magneto-rotational instability (MRI) in protoplanetary disks that have radially non-uniform magnetic field such that stable and unstable regions coexist initially, and found that a zone in which the disk…

天体物理学 · 物理学 2011-02-11 M. T. Kato , K. Nakamura , R. Tandokoro , M. Fujimoto , S. Ida

We present results from the first 3D kinetic numerical simulation of magnetorotational turbulence and dynamo, using the local shearing-box model of a collisionless accretion disc. The kinetic magnetorotational instability grows from a…

高能天体物理现象 · 物理学 2016-12-07 Matthew W. Kunz , James M. Stone , Eliot Quataert