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The distribution of atomic hydrogen in the Galactic plane is usually mapped using the Doppler shift of 21cm emission line. We calculate the emission spectrum in velocity slices of data (channel maps) and derive its dependence on the…

Astrophysics · Physics 2009-10-31 A. Lazarian , D. Pogosyan

Using fully kinetic 3D simulations, the reconnection dynamics of asymmetric current sheets are examined at the Earth's magnetopause. The plasma parameters are selected to model MMS magnetopause diffusion region crossings with guide fields…

With the assumption that the optical variability timescale is dominated by the cooling time of the synchrotron process for BL Lac objects, we estimate time dependent magnetic field strength of the emission region for two BL Lac objects. The…

High Energy Astrophysical Phenomena · Physics 2022-01-19 Xu-Liang Fan , Da-Hai Yan , Qing-Wen Wu , Xu Chen

We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally-driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop…

Astrophysics · Physics 2008-11-26 Takahiro Kudoh , Shantanu Basu , Youichi Ogata , Takashi Yabe

Aim: To study turbulence in the Orion Molecular Cloud (OMC1) by comparing observed and simulated characteristics of the gas motions. Method: Using a dataset of vibrationally excited H2 emission in OMC1 containing radial velocity and…

Astrophysics · Physics 2016-08-30 M. Gustafsson , A. Brandenburg , J. L. Lemaire , D. Field

(Abridged) Most massive protostars exhibit bipolar outflows. Nonetheless, there is no consensus regarding the mechanism at the origin of these outflows, nor on the cause of the less-frequently observed monopolar outflows. We aim to identify…

Solar and Stellar Astrophysics · Physics 2021-12-08 R. Mignon-Risse , M. González , B. Commerçon

HI data cubes are sources of unique information on interstellar turbulence. Doppler shifts due to supersonic motions contain information on turbulent velocity field which is otherwise difficult to obtain. However, the problem of separation…

Astrophysics · Physics 2007-05-23 A. Lazarian , D. Pogosyan , Alejandro Esquivel

We present a comprehensive study of MHD waves and instabilities in a weakly ionised system, e.g., an interstellar molecular cloud. We determine all the critical wavelengths of perturbations across which the sustainable wave modes can change…

Solar and Stellar Astrophysics · Physics 2011-04-01 Telemachos Ch. Mouschovias , Glenn E. Ciolek , S. A. Morton

Ambipolar diffusion is a physical mechanism related to the drift between charged and neutral particles in a partially ionized plasma that is key in many different astrophysical systems. However, understanding its effects is challenging due…

Solar and Stellar Astrophysics · Physics 2020-07-01 D. Nóbrega-Siverio , J. Martínez-Sykora , F. Moreno-Insertis , M. Carlsson

The role of turbulent fragmentation in regulating the efficiency of star formation in interstellar clouds is examined from new wide field imaging of 12CO and 13CO J=1-0 emission from the Rosette and G216-2.5 molecular clouds. The Rosette…

Astrophysics · Physics 2009-11-13 M. Heyer , J. Williams , C. Brunt

OB stars exhibit various types of spectral variability associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These are proposed to be caused by either magnetic fields or non-radial…

Using arguments parallel to those used in support of using H2CO as a sensitive probe of temperature and density in molecular clouds, we measured the J=7-6 and J=10-9 transitions of thioformaldehyde (H2CS) in several hot core sources. The…

Astrophysics of Galaxies · Physics 2009-07-24 Alwyn Wootten , Jeffrey G. Mangum

Kinetic helicity is a fundamental characteristics of astrophysical turbulent flows. It is not only responsible for the generation of large-scale magnetic fields in the Sun, stars, and spiral galaxies, but it also affects turbulent diffusion…

Fluid Dynamics · Physics 2025-05-15 Igor Rogachevskii , Nathan Kleeorin , Axel Brandenburg

We study the effects of ambipolar diffusion (AD) on hydromagnetic turbulence. In most of the cases, we use the single fluid approximation where the drift velocity between charged and neutral particles is proportional to the Lorentz force.…

Astrophysics of Galaxies · Physics 2019-06-13 Axel Brandenburg

Long-timescale simulations of the diffusion of a H$_2$O admolecule on the (0001) basal plane of ice Ih were carried out over a temperature range of 100 to 200 K using the adaptive kinetic Monte Carlo method and TIP4P/2005f interaction…

Computational Physics · Physics 2015-08-04 Andreas Pedersen , Leendertjan Karssemeijer , Herma M. Cuppen , Hannes Jónsson

We investigate the radial transport of magnetic flux in a thin accretion disc, the turbulence being modelled by effective diffusion coefficients (viscosity and resistivity). Both turbulent diffusion and advection by the accretion flow…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Jerome Guilet , Gordon I. Ogilvie

The atmospheres of massive O-type stars (O stars) are dynamic, turbulent environments resulting from radiatively driven instabilities over the iron bump, located slightly beneath the stellar surface. Here, complex radiation hydrodynamic…

We present our 12CO and 13CO mapping observations of SNR IC 443, interacting with molecular clouds. It is the first large scale high resolution 13CO mapping observation in the surrounding region. The morphologies of IC 443 in 12CO and 13CO…

Astrophysics of Galaxies · Physics 2009-12-02 Zhiyu Zhang , Yu Gao , Junzhi Wang

In the present-day universe, magnetic fields play such essential roles in star formation as angular momentum transport and outflow driving, which control circumstellar disc formation/fragmentation and also the star formation efficiency.…

Astrophysics of Galaxies · Physics 2022-12-28 Kenji Eric Sadanari , Kazuyuki Omukai , Kazuyuki Sugimura , Tomoaki Matsumoto , Kengo Tomida

(Abridged) In our previous work we found a statistically significant offset Delta V = 27 m/s between the radial velocities of the HC3N(2-1) and NH3(1,1) transitions observed in molecular cores from the Milky Way. This may indicate that the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 S. A. Levshakov , A. V. Lapinov , C. Henkel , P. Molaro , D. Reimers , M. G. Kozlov , I. I. Agafonova