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Filamentary structures are ubiquitous in the interstellar medium, yet their formation, internal structure, and longevity have not been studied in detail. We report the results from a comprehensive numerical study that investigates the…

Astrophysics of Galaxies · Physics 2015-11-18 Wladimir Banda-Barragán , Ross Parkin , Christoph Federrath , Roland Crocker , Geoffrey Bicknell

We present results from numerical modeling of emerging flux regions on the solar surface. The modeling was carried out by means of 3D radiative MHD simulations of the rise of buoyant magnetic flux tubes through the convection zone and into…

Astrophysics · Physics 2009-11-13 M. C. M. Cheung , M. Schuessler , T. D. Tarbell , A. M. Title

Diagnosing the spatial-temporal pattern of magnetic flux on the Sun is vital for understanding the origin of solar magnetism and activity. Here, we report a new form of flux appearance, magnetic outbreak, using observations with an…

Solar and Stellar Astrophysics · Physics 2023-01-04 Chunlan Jin , Guiping Zhou , Guiping Ruan , T. Baildon , Wenda Cao , Jingxiu Wang

To what extent magnetic fields affect how molecular clouds (MCs) fragment and create dense structures is an open question. We present a numerical study of cloud fragmentation using the SILCC-Zoom simulations. These simulations follow the…

Astrophysics of Galaxies · Physics 2023-07-26 S. Ganguly , S. Walch , D. Seifried , S. D. Clarke , M. Weis

Context: Photospheric flows create a network of often mixed-polarity magnetic field in the quiet Sun, where small-scale eruptions and network flares are commonly seen. Aims: The aim of this paper is (1) to describe the characteristics of…

Solar and Stellar Astrophysics · Physics 2017-05-31 R. Attie , D. E. Innes , S. K. Solanki , K. H. Glassmeier

We discuss evolution of the magnetic flux density and angular velocity in a molecular cloud core, on the basis of three-dimensional numerical simulations, in which a rotating magnetized cloud fragments and collapses to form a very dense…

Astrophysics · Physics 2009-11-13 Masahiro N Machida , Tomoaki Matsumoto , Kohji Tomisaka , Tomoyuki Hanawa

We investigate in detail the initial susceptibility, magnetization curves, and microstructure of ferrofluids in various concentration and particle dipole moment ranges by means of molecular dynamics simulations. We use the Ewald summation…

Soft Condensed Matter · Physics 2016-08-16 Zuowei Wang , Christian Holm , Hanns Walter Müller

Magnetic fields are dynamically important in the diffuse interstellar medium. Understanding how gravitationally bound, star-forming clouds form requires modeling of the fields in a self-consistent, supernova-driven, turbulent, magnetized,…

Astrophysics of Galaxies · Physics 2022-02-16 Juan C. Ibáñez-Mejía , Mordecai-Mark Mac Low , Ralf S. Klessen

Fragmentation and binary formation processes are studied using three-dimensional resistive MHD nested grid simulations. Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic field, we calculate the cloud evolution…

Astrophysics · Physics 2009-11-13 Masahiro N. Machida , Kohji Tomisaka , Tomoaki Matsumoto , Shu-ichiro Inutsuka

This paper reviews the studies of solar photospheric magnetic field evolution in active regions and its relationship to solar flares. It is divided into two topics, the magnetic structure and evolution leading to solar eruptions and the…

Solar and Stellar Astrophysics · Physics 2015-06-23 Haimin Wang , Chang Liu

We investigate the physical properties of dense cores formed in turbulent, magnetized, parsec-scale clumps of molecular clouds, using three-dimensional numerical simulations that include protostellar outflow feedback. The dense cores are…

Solar and Stellar Astrophysics · Physics 2015-05-28 Fumitaka Nakamura , Zhi-Yun Li

The magnetohydrodynamic evolution of a dense spherical cloud as it interacts with a strong planar shock is studied, as a model for shock interactions with density inhomogeneities in the interstellar medium. The cloud is assumed to be small…

Astrophysics · Physics 2009-04-13 Min-Su Shin , James M. Stone , Gregory F. Snyder

Stars form predominantly in clusters inside dense clumps of molecular clouds that are both turbulent and magnetized. The typical size and mass of the cluster-forming clumps are $\sim 1$ pc and $\sim 10^2 - $ 10$^3$ M$_\odot$, respectively.…

Astrophysics of Galaxies · Physics 2015-05-19 Fumitaka Nakamura , Zhi-Yun Li

We describe and analyze observations by the Solar Dynamics Observatory of the emergence of a small, bipolar active region within an area of unipolar magnetic flux that was surrounded by a circular, quiescent filament. Within only eight…

Solar and Stellar Astrophysics · Physics 2018-08-08 Sally Dacie , Tibor Torok , Pascal Demoulin , Mark Linton , Cooper Downs , Lidia van Driel-Gesztelyi , David Long , James Leake

A weak fluctuating magnetic field embedded into a turbulent conducting medium grows exponentially while its characteristic scale decays. In the ISM and protogalactic plasmas, the magnetic Pr is very large, so a broad spectrum of growing…

Astrophysics · Physics 2008-11-26 Alexander Schekochihin , Steven Cowley , Jason Maron , Leonid Malyshkin

We investigate the formation and evolution of giant molecular clouds (GMCs) by the collision of convergent warm neutral medium (WNM) streams in the interstellar medium, in the presence of magnetic fields and ambipolar diffusion (AD),…

Three-dimensional electron phase space holes are shown to be positive charges on the plasma background which produce a radial electric field and force the trapped electron component into an azimuthal drift. In this way electron holes…

Space Physics · Physics 2012-04-20 R. A. Treumann , W. Baumjohann

We study the evolution of an inflation-generated magnetic field, due to its coupling to fluid motions, during cosmological phase transitions. We find that the magnetic field stays almost unchanged on large scales, while on small scales the…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-30 Tina Kahniashvili , Axel Brandenburg , Leonardo Campanelli , Bharat Ratra , Alexander G. Tevzadze

We report a unique conjugate observation of fast flows and associated current sheet disturbances in the near-Earth magnetotail by MMS (Magnetospheric Multiscale) and Cluster preceding a positive bay onset of a small substorm at ~14:10 UT,…

Dynamos in the Sun and other bodies tend to produce magnetic fields that possess magnetic helicity of opposite sign at large and small scales, respectively. The build-up of magnetic helicity at small scales provides an important saturation…

Solar and Stellar Astrophysics · Physics 2010-11-30 Piyali Chatterjee , Gustavo Guerrero , Axel Brandenburg