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Gravity plays a determining role in the evolution of the molecular ISM. In \citet{2016arXiv160304342L}, we proposed a measure called gravitational energy spectrum to quantify the importance of gravity on multiple physical scales. In this…

太阳与恒星天体物理 · 物理学 2016-10-03 Guang-Xing Li , Andreas Burkert

Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: weakness of collisional dissipation and…

太阳与恒星天体物理 · 物理学 2015-06-16 Olga Alexandrova , Christopher H. K. Chen , Luca Sorriso-Valvo , Timothy S. Horbury , Stuart D. Bale

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…

太阳与恒星天体物理 · 物理学 2011-04-01 Telemachos Ch. Mouschovias , Glenn E. Ciolek , S. A. Morton

We investigate turbulent properties of the non-star-forming, translucent molecular cloud, MBM16 by applying the statistical technique of a two-dimensional spatial power spectrum (SPS) on the neutral hydrogen (HI) observations obtained by…

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…

星系天体物理 · 物理学 2019-08-10 Y. Zhang , Z. Guo , H. H. Wang , H-b Li

Theoretical and observational studies on the turbulence of the interstellar medium developed fast in the past decades. The theory of supersonic magnetized turbulence, as well as the understanding of projection effects of observed…

星系天体物理 · 物理学 2015-05-18 D. Falceta-Goncalves , A. Lazarian , M. Houde

Most numerical investigations on the role of magnetic fields in turbulent molecular clouds (MCs) are based on ideal magneto-hydrodynamics (MHD). However, MCs are weakly ionized, so that the time scale required for the magnetic field to…

天体物理学 · 物理学 2009-11-13 Pak Shing Li , Christopher F. McKee , Richard I. Klein , Robert T. Fisher

The strengths of magnetic fields in interstellar gas clouds are obtained through observations of the circular polarization of spectral line radiation. Irregularities in this magnetic field may be present due to turbulence, waves or perhaps…

天体物理学 · 物理学 2009-10-31 W. D. Watson , D. S. Wiebe , R. M. Crutcher

The magnetic field strength in molecular clouds is a fundamental quantity for theories of star formation. It is estimated by Zeeman splitting measurements in a few dense molecular cores, but its volume--averaged value within large molecular…

天体物理学 · 物理学 2009-11-10 Paolo Padoan , Raul Jimenez , Mika Juvela , Aake Nordlund

We study the magnetic field to density ($B-\rho$) relation in turbulent molecular clouds with dynamically important magnetic fields using nonideal three-dimensional magnetohydrodynamic simulations. Our simulations show that there is a…

星系天体物理 · 物理学 2022-03-30 Sayantan Auddy , Shantanu Basu , Takahiro Kudoh

The degree of linear polarization has recently been found to show wide random variations over the solar disk. These variations are presumably at least partly due to fluctuations in the flux density of turbulent photospheric magnetic fields…

天体物理学 · 物理学 2007-05-23 K. Petrovay

The Zeeman effect and dust grain alignment are two major methods for probing magnetic fields (B-fields) in molecular clouds, largely motivated by the study of star formation, as the B-field may regulate gravitational contraction and channel…

星系天体物理 · 物理学 2021-06-16 Hua-bai Li

We present an investigation on effect of the ion-neutral (or ambipolar) diffusion heating rate on thermal phases of a molecular cloud. We use the modeling of ambipolar diffusion with two-fluid smoothed particle hydrodynamics, as discussed…

天体物理学 · 物理学 2008-04-29 M. Nejad-Asghar , D. Molteni

We simulate fragmentation and gravitational collapse of cold, magnetized molecular clouds. We explore the nonlinear development of an instability mediated by ambipolar diffusion, in which the collapse rate is intermediate to fast…

天体物理学 · 物理学 2009-10-31 R. Indebetouw , E. G. Zweibel

The rotational properties of centrally condensed, turbulent molecular cloud cores with velocity fields that are characterized by Gaussian random fields are investigated. It is shown that the observed line width-size relationship can be…

天体物理学 · 物理学 2009-10-31 Andreas Burkert , Peter Bodenheimer

Recent observations have revealed that the ion-neutral drift velocity in star-forming molecular clouds and dense cores is on the order of 100 m s^-1. Theoretical studies have shown that, in ambipolar diffusion, the process responsible for…

星系天体物理 · 物理学 2026-02-05 Haruka Fukihara , Yusuke Tsukamoto , Hiroyuki Hirashita , Doris Arzoumanian , Yoshiaki Misugi

Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between $0.06 ~ \lesssim R ~\lesssim 1$ au. The spectrum is studied as a function of scale, normalized to the ion inertial scale…

It is generally believed that turbulence has a significant impact on the dynamics and evolution of molecular clouds and the star formation which occurs within them. Non-ideal magnetohydrodynamic effects are known to influence the nature of…

星系天体物理 · 物理学 2015-03-17 Turlough P. Downes , Stephen O'Sullivan

We study the effect of the non-linear process of ambipolar diffusion (joint transport of magnetic flux and charged particles relative to neutral particles) on the long-term behavior of a non-uniform magnetic field in a one-dimensional…

太阳与恒星天体物理 · 物理学 2015-05-18 Jaime Hoyos , Andreas Reisenegger , Juan Valdivia

We present the results of an extensive Arecibo observational survey of magnetic field strengths in the inter-core regions of molecular clouds to determine their role in the evolution and collapse of molecular clouds as a whole. Sensitive 18…

星系天体物理 · 物理学 2019-10-16 K. L. Thompson , T. H. Troland , C. Heiles