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The magnetic energy of nonlinear Alfven waves in compressible plasmas may be ponderomotively coupled only to ion-acoustic quasi-modes which modulate the wave phase velocity and cause wave-front steepening. In the collisionless plasma with…

Astrophysics · Physics 2009-10-31 M. V. Medvedev

In magnetized, stratified astrophysical environments such as the Sun's corona and solar wind, Alfv\'enic fluctuations ''reflect'' from background gradients, enabling nonlinear interactions and thus dissipation of their energy into heat.…

Solar and Stellar Astrophysics · Physics 2023-08-22 Romain Meyrand , Jonathan Squire , Alfred Mallet , Benjamin D. G. Chandran

We (Li et al. 2009; Paper-I) compared the magnetic field directions inferred from polarimetry data obtained from 100-pc scale inter-cloud media (ICM) and from sub-pc scale molecular cloud cores. The highly correlated result led us to…

Astrophysics of Galaxies · Physics 2019-08-10 Y. Zhang , Z. Guo , H. H. Wang , H-b Li

We use magnetic collapse models to place some constraints on the formation and angular momentum evolution of circumstellar disks which are embedded in magnetized cloud cores. Previous models have shown that the early evolution of a…

Astrophysics · Physics 2009-10-30 Shantanu Basu

The structure of accretion curtain flows arising from magnetically disrupted discs is considered. It is shown that a sub-Alfvenic, magnetically channelled flow is consistent with matching the magnetic field across the curtain base. It is…

Solar and Stellar Astrophysics · Physics 2015-05-30 C. G. Campbell

Sharp fronts observed by Chandra satellite between dense cool cluster cores moving with near-sonic velocity through the hotter intergalactic gas, require strong suppression of thermal conductivity across the boundary. This may be due to…

Astrophysics · Physics 2009-11-11 Maxim Lyutikov

In the standard scenario of isolated low-mass star formation, strongly magnetized molecular clouds are envisioned to condense gradually into cores, driven by ambipolar diffusion. Once the cores become magnetically supercritical, they…

Astrophysics · Physics 2007-05-23 Fumitaka Nakamura , Zhi-Yun Li

We introduce a Monte Carlo model of nonlinear diffusive shock acceleration allowing for the generation of large-amplitude magnetic turbulence. The model is the first to include strong wave generation, efficient particle acceleration to…

Astrophysics · Physics 2008-11-26 Andrey Vladimirov , Donald C. Ellison , Andrei Bykov

We model the coagulation and fragmentation of dust grains during the protostellar collapse with our newly developed shark code. It solves the gas-dust hydrodynamics in a spherical geometry and the coagulation/fragmentation equation. It also…

Astrophysics of Galaxies · Physics 2022-11-16 Ugo Lebreuilly , Valentin Vallucci-Goy , Vincent Guillet , Maxime Lombart , Pierre Marchand

Using self-gravitational hydrodynamical numerical simulations, we investigated the evolution of high-density turbulent molecular clouds swept by a colliding flow. The interaction of shock waves due to turbulence produces networks of thin…

Solar and Stellar Astrophysics · Physics 2015-06-23 Tomoaki Matsumoto , Kazuhito Dobashi , Tomomi Shimoikura

In giant molecular clouds (GMCs), shocks driven by converging turbulent flows create high-density, strongly-magnetized regions that are locally sheetlike. In previous work, we showed that within these layers, dense filaments and embedded…

Astrophysics of Galaxies · Physics 2015-10-21 Che-Yu Chen , Eve C. Ostriker

We study the effect of superfluidity on torsional oscillations of highly magnetised neutron stars (magnetars) with a microphysical equation of state by means of two-dimensional, magnetohydrodynamical- elastic simulations. The superfluid…

High Energy Astrophysical Phenomena · Physics 2016-06-08 Michael Gabler , Pablo Cerdá-Durán , Nikolaos Stergioulas , José A. Font , Ewald Müller

The formation of protoplanetary discs during the collapse of molecular dense cores is significantly influenced by angular momentum transport, notably by the magnetic torque. In turn, the evolution of the magnetic field is determined by…

Astrophysics of Galaxies · Physics 2017-02-01 Patrick Hennebelle , Benoit Commercon , Gilles Chabrier , Pierre Marchand

The formation and evolution of a circumstellar disk in magnetized cloud cores is investigated from prestellar core stage until sim 10^4 yr after protostar formation. In the circumstellar disk, fragmentation first occurs due to gravitational…

Solar and Stellar Astrophysics · Physics 2015-05-27 Masahiro N. Machida , Shu-ichiro Inutsuka , Tomoaki Matsumoto

We use 3D numerical MHD simulations to follow the evolution of cold, turbulent, gaseous systems with parameters representing GMC conditions. We study three cloud simulations with varying mean magnetic fields, but identical initial velocity…

Astrophysics · Physics 2008-11-26 Eve C. Ostriker , James M. Stone , Charles F. Gammie

Possible effects of magnetic fields in core collapse supernovae rely on an efficient amplification of the weak pre-collapse fields. It has been suggested that the magneto-rotational instability (MRI) leads to rapid field growth. Although…

Astrophysics · Physics 2009-05-06 M. Obergaulinger , P. Cerdà-Duràn , E. Müller , M. A. Aloy

We investigate the formation of circumstellar disks and outflows subsequent to the collapse of molecular cloud cores with the magnetic field and turbulence. Numerical simulations are performed by using an adaptive mesh refinement to follow…

Solar and Stellar Astrophysics · Physics 2017-04-26 Tomoaki Matsumoto , Masahiro N. Machida , Shu-ichiro Inutsuka

We report results from twelve simulations of the collapse of a molecular cloud core to form one or more protostars, comprising three field strengths (mass-to-flux ratios, {\mu}, of 5, 10, and 20) and four field geometries (with values of…

Solar and Stellar Astrophysics · Physics 2017-08-28 Benjamin T. Lewis , Matthew R. Bate

We present a model in which the supersonic motions observed in molecular clouds are driven by gravitational energy released as large structures fragment into smaller ones. The fragmentation process begins in large molecular clouds, and…

Astrophysics · Physics 2007-10-16 George B. Field , Eric G. Blackman , Eric Keto

Recent observations have established that the magnetosphere is a system of natural complexity. The co-existence of multi-scale structures such as auroral arcs, turbulent convective flows, and scale-free distributions of energy perturbations…

Plasma Physics · Physics 2015-05-19 William W. Liu , Laura F. Morales , Vadim M. Uritsky , Paul Charbonneau