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Magnetic diffusion plays a vital role in star formation. We trace its influence from interstellar cloud scales down to star-disk scales. On both scales, we find that magnetic diffusion can be significantly enhanced by the buildup of strong…

Solar and Stellar Astrophysics · Physics 2013-08-19 Shantanu Basu , Wolf B. Dapp

We study the magnetic interaction between a neutron star and its disk by solving the time-dependent relativistic force-free equations. At the initial state, we assume that the dipole magnetic field of the neutron star connects the neutron…

Astrophysics · Physics 2015-06-24 Eiji Asano , Toshio Uchida , Ryoji Matsumoto

Magnetic fields are an elemental part of the interstellar medium in galaxies. However, their impact on gas dynamics and star formation in galaxies remains controversial. We use a suite of global magnetohydrodynamical simulations of isolated…

Astrophysics of Galaxies · Physics 2019-09-25 Bastian Körtgen , Robi Banerjee , Ralph E. Pudritz , Wolfram Schmidt

We study the distribution of orbital eccentricities of stars in thick disks generated by the heating of a pre-existing thin stellar disk through a minor merger (mass ratio 1:10), using N-body/SPH numerical simulations of interactions that…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 P. Di Matteo , M. D. Lehnert , Y. Qu , W. van Driel

We model gas inflow patterns onto circumstellar disks and the evolution of the pseudodisk using three-dimensional resistive MHD simulations. Starting from a prestellar core without turbulence and with a misalignment between the initial…

Solar and Stellar Astrophysics · Physics 2026-02-10 Masahiro N. Machida , Shingo Hirano , Shantanu Basu

Dynamical collapses of magnetized molecular cloud cores are studied with magnetohydrodynamical simulations from the run-away collapse phase to the accretion phase. In the run-away collapse phase, a disk threaded by magnetic field lines is…

Astrophysics · Physics 2009-10-30 Kohji Tomisaka

Magnetar magnetospheres are strongly twisted, and are able to power sudden energetic events through the rapid release of stored electromagnetic energy. In this paper, we investigate twisted relativistic force-free axisymmetric…

High Energy Astrophysical Phenomena · Physics 2023-11-15 D. Ntotsikas , K. N. Gourgouliatos , I. Contopoulos , S. K. Lander

The dynamics and structure of accretion disks, which accumulate the vertical magnetic field in the centers, are investigated using two- and three-dimensional MHD simulations. The central field can be built up to the equipartition level and…

Astrophysics · Physics 2009-11-13 Igor V. Igumenshchev

We consider the radial buoyancy of vertical magnetic field lines in radiation and gas pressure dominated accretion disks. We find that in addition to radial drift driven by turbulent diffusion and biased by the global field geometry, there…

Astrophysics · Physics 2009-10-28 Seok Jae Park , Ethan T. Vishniac

We present global 3D MHD simulations of geometrically thin but unstratified accretion disks in which a near Keplerian disk rotates between two bounding regions with initial rotation profiles that are stable to the MRI. The inner region…

Astrophysics · Physics 2015-05-27 Adriane Steinacker , John C. B. Papaloizou

The magnetic fields of accretion disks play an important role in studying their evolution. We may assume that its generation is connected to the dynamo mechanism, which is similar with that in the galactic disks. Here, we propose a model of…

High Energy Astrophysical Phenomena · Physics 2021-08-11 Daniela V. Boneva , Evgeny A. Mikhailov , Maria V. Pashentseva , Dmitriy D. Sokoloff

We investigate under which conditions cold, fan-shaped winds can be steadily launched from thin (Keplerian) accretion discs. Such winds are magneto-centrifugal winds launched from a thin annulus in the disc, along open magnetic field lines…

Solar and Stellar Astrophysics · Physics 2015-06-11 Jonathan Ferreira , Fabien Casse

We describe the results of numerical "2.5--dimensional" MHD simulations of an initially unmagnetized disk model orbiting a central point--mass and responding to the continual generation of poloidal magnetic field due to a secular source…

Astrophysics · Physics 2009-11-13 Dimitris M. Christodoulou , Ioannis Contopoulos , Demosthenes Kazanas

Activity of the nuclei of galaxies and stellar mass systems involving disk accretion to black holes is thought to be due to (1) a small-scale turbulent magnetic field in the disk (due to the magneto-rotational instability or MRI) which…

High Energy Astrophysical Phenomena · Physics 2009-08-05 R. V. E. Lovelace , D. M. Rothstein , G. S. Bisnovatyi-Kogan

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…

Astrophysics · Physics 2009-10-31 Brigitta von Rekowski , Axel Brandenburg , Wolfgang Dobler , Anvar Shukurov

Magnetic reconnection in the partially ionized solar chromosphere is studied in 2.5-dimensional magnetohydrodynamic simulations including radiative cooling and ambipolar diffusion. A Harris current sheet with and without a guide field is…

Solar and Stellar Astrophysics · Physics 2015-09-24 Lei Ni , Bernhard Kliem , Jun Lin , Ning Wu

Strong magnetic fields play a crucial role in the removal of angular momentum from collapsing clouds and protostellar discs and are necessary for the formation of disc winds as well as jets from the inner disc and indeed, strong large-scale…

Solar and Stellar Astrophysics · Physics 2015-06-03 Jonathan Braithwaite

The origin of disks surrounding young stars has direct implications for our understanding of the formation of planetary systems. In the interstellar clouds from which star form, angular momentum is regulated by magnetic fields, preventing…

Astrophysics · Physics 2007-05-23 Michiel R. Hogerheijde

Non-ideal MHD effects have been shown recently as a robust mechanism of averting the magnetic braking "catastrophe" and promoting protostellar disc formation. However, the magnetic diffusivities that determine the efficiency of non-ideal…

Solar and Stellar Astrophysics · Physics 2021-05-12 Bo Zhao , Paola Caselli , Zhi-Yun Li , Ruben Krasnopolsky , Hsien Shang , Ka Ho Lam

In this paper we consider the effect of a self-consistently computed magnetosdisc field structure on the magnetosphere-ionosphere coupling current system at Jupiter. We find that the azimuthal current intensity, and thus the stretching of…

Space Physics · Physics 2015-05-30 J. D. Nichols