Santos-Lima, R., Lazarian, A., Cho, J.
The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology or reconnect in highly conducting media....
Reconnection in weakly stochastic B-fields in 2D (2009)
Kulpa-Dybel, K., Kowal, G., Otmianowska-Mazur, K., Lazarian, A., Vishniac, E.
We study two dimensional turbulent magnetic reconnection in a compressible fluid in the gas pressure dominated limit. We use open boundary conditions and start from a Harris current sheet...
Turbulence-induced magnetic fields and the structure of Cosmic Ray modified shocks (2009)
Beresnyak, A., Jones, T. W., Lazarian, A.
We propose a model for Diffusive Shock Acceleration (DSA) in which stochastic magnetic fields in the shock precursor are generated through purely fluid mechanisms of a so-called small-scale dynamo....
Extending Big Power Law in the Sky with Turbulence Spectra from WHAM data (2009)
We use the data of Wisconsin H$\alpha$ Mapper (WHAM) to test the hypothesis of whether the amplitudes and spectrum of density fluctuations measured by WHAM may be matched to the data obtained for...
Tsallis statistics as a tool for studying interstellar turbulence (2009)
We used magnetohydrodynamic (MHD) simulations of interstellar turbulence to study the probability distribution functions (PDFs) of increments of density, velocity, and magnetic field. We found that...
A model of acceleration of Anomalous Cosmic Rays by Reconnection in the Heliosheath (2009)
We discuss a model of cosmic ray acceleration that accounts for the observations of anomalous cosmic rays by Voyager 1 and 2. The model appeals to fast magnetic reconnection rather than shocks as the...
Structure of Stationary Strong Imbalanced Turbulence (2009)
In this paper we systematically study the spectrum and structure of incompressible MHD turbulence by means of high resolution direct numerical simulations. We considered both balanced and imbalanced...
Simulations of Electron Magnetohydrodynamic Turbulence (2009)
We present numerical simulations of electron magnetohydrodynamic (EMHD) and electron reduced MHD (ERMHD) turbulence. Comparing scaling relations, we find that both EMHD and ERMHD turbulence show...
Numerical Tests of Fast Reconnection in Weakly Stochastic Magnetic Fields (2009)
Kowal, G., Lazarian, A., Vishniac, E. T., Otmianowska-Mazur, K.
We study the effects of turbulence on magnetic reconnection using 3D numerical simulations. This is the first attempt to test a model of fast magnetic reconnection in the presence of weak turbulence...
Quantitative Theory of Grain Alignment: Probing Grain Environment and Grain Composition (2009)
While the problem of grain alignment was posed more than 60 years ago the quantitative model of grain alignment that can account for the observed polarization arising from aligned grains has been...
How do Galaxies Accrete Gas and Form Stars? (2009)
Putman, M. E., Henning, P., Bolatto, A., Keres, D., Pisano, D. J., Rosenberg, J., ...
Great strides have been made in the last two decades in determining how galaxies evolve from their initial dark matter seeds to the complex structures we observe at z=0. The role of mergers has been...
Understanding of the role of magnetic fields: Galactic perspective (2009)
Lazarian, A., Boldyrev, S., Forest, C., Sarff, J., Terry, P.
A combination of observation, theory, modeling, and laboratory plasma experiments provides a multifaceted approach to develop a much greater understanding of how magnetic fields arise in galactic...
Line-of-sight statistical methods for turbulent medium: VCS for emission and absorption lines (2009)
We present an overview of the Velocity Coordinate Spectrum (VCS), a new technique for studying astrophysical turbulence that utilizes the line-of-sight statistics of Doppler-broadened spectral lines....
Statistics of Centroids of Velocity (2009)
We review the use of velocity centroids statistics to recover information of interstellar turbulence from observations. Velocity centroids have been used for a long time now to retrieve information...
Polarization of FIR emission from T Tauri Disks (2008)
Recent observation of 850 micron sub-mm polarization from T Tauri disks opens up the possibility of studying magnetic field structure within protostellar disks. The degree of polarization is around 3...
Alignment of Dust by Radiative Torque: Recent Developments (2008)
Alignment of dust by radiative torques (RATs) has proven to be the most promising mechanism to explain alignment in various astrophysical environments, from comet atmospheres to accretion disks,...
Model of Reconnection of Weakly Stochastic Magnetic Field and its Testing (2008)
Lazarian, A., Vishniac, E., Kowal, G.
Astrophysical fluids are generically turbulent, which means that frozen-in magnetic fields are, at least, weakly stochastic. Therefore realistic studies of astrophysical magnetic reconnection should...
Studying ISM magnetic fields and turbulent regimes from polarimetric maps (2008)
Falceta-Goncalves, D., Lazarian, A., Kowal, G.
Polarimeric maps have been used on the characterization of the magnetic field in molecular clouds. However, it is difficult to determine the 3-dimensional properties of these regions from the...
We present statistical analysis of diffuse Galactic synchrotron emission and polarized thermal emission from dust. Both Galactic synchrotron emission and polarized thermal emission from dust reflect...
Numerical Studies of Weakly Stochastic Magnetic Reconnection (2008)
Kowal, G., Lazarian, A., Vishniac, E. T., Otmianowska-Mazur, K.
We study the effects of turbulence on magnetic reconnection using three-dimensional numerical simulations. This is the first attempt to test a model of fast magnetic reconnection proposed by Lazarian...
Model of Reconnection of Weakly Stochastic Magnetic Field and its Implications (2008)
We discuss the model of magnetic field reconnection in the presence of turbulence introduced by us approximately ten years ago. The model does not require any plasma effects to be involved in order...
Grain Alignment by Radiative Torques (2008)
Grain alignment is a notoriously difficult problem, that is extremely rich in underlying physics. The long history of attempts theoretical handling of the problem resulted in rather sceptical...
Growth of Magnetic Fields Induced by Turbulent Motions (2008)
Cho, J., Vishniac, E., Beresnyak, A., Lazarian, A., Ryu, D.
We present numerical simulations of driven magnetohydrodynamic (MHD) turbulence with weak/moderate imposed magnetic fields. The main goal is to clarify dynamics of magnetic field growth. We also...
CMBPol Mission Concept Study: Foreground Science Knowledge and Prospects (2008)
Fraisse, A. A., Brown, J. -A. C., Dobler, G., Dotson, J. L., Draine, B. T., Frisch, P. C., ...
We report on our knowledge of Galactic foregrounds, as well as on how a CMB satellite mission aiming at detecting a primordial B-mode signal (CMBPol) will contribute to improving it. We review the...
Grain Alignment and CMB Polarization Studies (2008)
Polarized microwave emission from dust is an important foreground that may contaminate polarized CMB studies unless carefully accounted for. Modeling of polarization from dust requires a quantitative...
Burkhart, Blakesley, Falceta-Goncalves, D., Kowal, G., Lazarian, A.
We present a number of statistical tools for obtaining studying turbulence in molecular clouds and diffuse interstellar medium. For our tests we used of three-dimensional 512 cube compressible MHD...
Lazarian, A., Beresnyak, A., Yan, H., Opher, M., Liu, Y.
Astrophysical fluids, including interstellar and interplanetary medium, are magnetized and turbulent. Their appearance, evolution, and overall properties are determined by the magnetic turbulence...
Obtaining Spectra of Turbulent Velocity from Observations (2008)
We discuss a long-standing problem of how turbulence can be studied using observations of Doppler broadened emission and absorption lines. The focus of the present review is on two new techniques,...
Turbulent motions induce Doppler shifts of observable emission and absorption lines motivating studies of turbulence using precision spectroscopy. We provide the numerical testing of the two most...
We discuss a new technique of studying magnetic fields in diffuse astrophysical media, e.g. interstellar and intergalactic gas/plasma. This technique is based on the angular momentum alignment of...
The Effects of Clumps in Explaining X-ray Emission Lines from Hot Stars (2008)
Cassinelli, J. P., Ignace, R., Waldron, W. L., Cho, J., Murphy, N. A., Lazarian, A.
It is now well established that stellar winds of hot stars are fragmentary and that the X-ray emission from stellar winds has a strong contribution from shocks in winds. Chandra high spectral...
FAST RECONNECTION OF MAGNETIC FIELDS IN TURBULENT FLUIDS (2008)
La reconección es el proceso mediante el cual los campos magnéticos cambian de topología en un medio conductor, y es fundamental para entender diferentes procesos, incluyendo la turbulencia...
Particle Acceleration by Fast Modes in Solar Flares (2008)
Yan, Huirong, Lazarian, A., Petrosian, V.
We address the problem of particle acceleration in solar flares by fast modes which may be excited during the reconnection and undergo cascade and are subjected to damping. We extend the calculations...
We continue our work on developing techniques for studying turbulence with spectroscopic data. We show that Doppler-broadened absorption spectral lines, in particularly, saturated absorption lines,...
Falceta-Goncalves, D., Lazarian, A., Kowal, G.
Polarimetry is extensively used as a tool to trace the interstellar magnetic field projected on the plane of sky. Moreover, it is also possible to estimate the magnetic field intensity from...
Whittet, D.C.B., Hough, J., Lazarian, A., Hoang, T.
Original article can be found at: http://www.iop.org/EJ/journal/apj Copyright American Astronomical Society. DOI: 10.1086/525040 [Full text of this article is not available in the UHRA]
Density Statistics of Compressible MHD Turbulence (2007)
Lazarian, A., Kowal, G., Beresnyak, A.
Density is the turbulence statistics that is most readily available from observations. Different regimes of turbulence correspond to different density spectra. For instance, the viscosity-damped...
We consider grains with superparamagnetic inclusions and report two new condensed matter effects that can enhance the internal relaxation of the energy of a wobbling grain, namely, superparamagnetic...
Radiative torques alignment in the presence of pinwheel torques (2007)
We study the alignment of grains subject to both radiative torques and pinwheel torques while accounting for thermal flipping of grains. By pinwheel torques we refer to all systematic torques that...
Cosmic ray transport in MHD turbulence (2007)
Numerical simulations shed light onto earlier not trackable problem of magnetohydrodynamic (MHD) turbulence. They allowed to test the predictions of different models and choose the correct ones....
Reconnection in the ISM (2007)
We discuss the role of ambipolar diffusion for simple reconnection in a partially ionized gas, following the reconnection geometry of Parker and Sweet. When the recombination time is short the...
Interstellar filaments and the statistics of galactic HI (2007)
Lazarian Pogosyan, A. Lazarian, D. Pogosyan
This paper presents a statistical explanation of filament formation in the galactic atomic hydrogen. We claim that even in the absence of dynamical factors the Gaussian field corresponding to the...
Microwave emission by dust: mechanisms, properties and prospects for ISM studies (2007)
Lazarian Princeton, A. Lazarian
. I review my work with Bruce Draine on dust emissivity at microwave frequencies (3 cm - 3 mm). This emissivity explains the recently detected "anomalous" component of the galactic...
Reconnection in a Weakly Stochastic Field (2007)
A. Lazarian, Ethan T. Vishniac
We examine the effect of weak, small scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale...
Cosmic Rays and Grain Alignment (2007)
Lazarian And, A. Lazarian, W. G. Roberge
The recent detection of interstellar polarization in the solid CO feature near 4.67 ¯m shows that CO-mantled grains can be aligned in cold molecular clouds. These observations conflict with a theory...
Gold Alignment Internal Dissipation (2007)
Lazarian Astronomy, A. Lazarian
The measures of mechanical alignment were obtained for both prolate and oblate grains when their temperature is comparable with grain kinetic energy devided by k, the Boltzmann constant. For such...
Inelastic Dissipation in Tumbling Asteroids and Comets (2007)
Michael Efroimsky, A. Lazarian
Asteroids and comets dissipate energy when they rotate about the axis different from the axis of the maximal moment of inertia. We show that the most efficient internal relaxation happens at the...
Resonance Paramagnetic Relaxation and Alignment of Ultrasmall Grains (2007)
Lazarian Princeton, A. Lazarian
. A mechanism of enhanced paramagnetic relaxation for rapidly rotating interstellar grains is presented. We show that the Barnett magnetization that arises from grain rotation ensures that...
Disorientation of Suprathermally Rotating Grains and the Grain Alignment Problem (2007)
Lazarian Draine, A. Lazarian, B. T. Draine
We discuss the dynamics of dust grains subjected to uncompensated torques arising from H 2 formation. In particular, we discuss grain dynamics when a grain spins down and goes through a...
Barnett Relaxation in Thermally-Rotating Grains (2007)
We present an exact formulation of the physics of Barnett relaxation. Our formulation is based on a realistic kinetic model of the relaxation mechanism which includes the alignment of the grain...
Thermal Flipping and Thermal Trapping -- New Elements in Dust Grain Dynamics (2007)
Lazarian Draine, A. Lazarian, B. T. Draine
Since the classical work by Purcell (1979) it has been generally accepted that most interstellar grains rotate suprathermally. Suprathermally rotating grains would be nearly perfectly aligned with...
Inelastic Dissipation in a Freely Rotating Body. Application to Cosmic-Dust Alignment. (2007)
A. Lazarian, Michael Efroimsky
Motivated by a recent study by Lazarian and Draine, which showed that a high degree of grain alignment of the paramagnetic dust is achievable if the rates of internal relaxation are controlled by the...
Davis-Greenstein alignment of oblate spheroidal grains (2007)
Roberge Lazarian, W. G. Roberge, A. Lazarian
We present extensive calculations on the efficiency of grain alignment by the Davis-Greenstein mechanism. We model the grains as oblate spheroids with arbitrary axis ratios. Our description of the...
Paramagnetic Alignment of Thermally Rotating Dust (2007)
Lazarian Received, A. Lazarian
Paramagnetic alignment of thermally rotating oblate dust grains is studied analytically for finite ratios of grain to gas temperatures. For such ratios, the alignment of angular momentum J in respect...
What Grain Alignment Can Tell About Circumstellar Discs and Comets (2007)
Lazarian Canadian, A. Lazarian
Grain alignment theory suggests that grains should be aligned in circumstellar regions and the observational data available supports this conclusion. We discuss the alignment of grains via (1)...
COMPRESSIBLE MHD TURBULENCE: MODE COUPLING, ANISOTROPIES, AND SCALINGS (2007)
entre los investigadores. Sin embargo, avances recientes en el entendimiento teórico de la magnetohidrodinámica incompresible además de un mejoramiento en las capacidades computacionales han...
Revmexaa Serie De, J. Cho, A. Lazarian
Compressible turbulence, especially the magnetized version of it, traditionally has a bad reputation with researchers. However, recent progress in the theoretical understanding of incompressible MHD,...
FAST RECONNECTION OF MAGNETIC FIELDS IN TURBULENT FLUIDS (2007)
La reconeccion es el proceso mediante el cual los campos magneticos cambian de topologa en un medio conductor, y es fundamental para entender diferentes procesos, incluyendo la turbulencia...
Revmexaa Serie De, A. Esquivel, A. Lazarian
icular, LP00 found that for a steep density eld (n < 3), when the channels are thin (thickness smaller than the turbulent dispersion at a given scale) the spectrum is dominated by the velocity,...
Far-infrared polarimetry from the Stratospheric Observatory for Infrared Astronomy (2007)
Vaillancourt, J. E., Chuss, D. T., Crutcher, R. M., Dotson, J. L., Dowell, C. D., Harper, D. A., ...
Multi-wavelength imaging polarimetry at far-infrared wavelengths has proven to be an excellent tool for studying the physical properties of dust, molecular clouds, and magnetic fields in the...
Topology of Neutral Hydrogen Within the Small Magellanic Cloud (2007)
Chepurnov, A., Lazarian, A., Gordon, J., Stanimirovic, S.
In this paper, genus statistics have been applied to an HI column density map of the Small Magellanic Cloud in order to study its topology. To learn how topology changes with the scale of the system,...
Whittet, D. C. B., Hough, J. H., Lazarian, A., Hoang, Thiem
A detailed study of interstellar polarization efficiency toward molecular clouds is used to attempt discrimination between grain alignment mechanisms in dense regions of the ISM. Background field...
Atomic alignment and Diagnostics of Magnetic Fields in Diffuse Media (2007)
We continue our studies of atomic alignment in diffuse media, in particularly, in interstellar and circumstellar media, with the goal of developing new diagnostics of magnetic fields in these...
Nonlinear damping of slab modes and cosmic ray transport (2007)
Shalchi, A., Lazarian, A., Schlickeiser, R.
By applying recent results for the slab correlation time scale onto cosmic ray scattering theory, we compute cosmic ray parallel mean free paths within the quasilinear limit. By employing these...
Cosmic Ray Propagation: Nonlinear Diffusion Parallel and Perpendicular to Mean Magnetic Field (2007)
We consider the propagation of cosmic rays in turbulent magnetic fields. We use the models of magnetohydrodynamic turbulence that were tested in numerical simulations, in which the turbulence is...
Strong Imbalanced Turbulence (2007)
We consider stationary, forced, imbalanced, or cross-helical MHD Alfvenic turbulence where the waves traveling in one direction have higher amplitudes than the opposite waves. This paper is dedicated...
Aspects of Density Fluctuations in Compressible MHD Turbulence (2007)
We study scaling relations of compressible isothermal strongly magnetized turbulence using numerical simulations with resolution 512$^3$. We find a good correspondence of our results with the Fleck...
Tracing Magnetic Fields with Aligned Grains (2007)
Magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g., transport of heat), and cosmic rays. One of the...
Scaling Relations of Compressible MHD Turbulence (2007)
We study scaling relations of compressible strongly magnetized turbulence. We find a good correspondence of our results with the Fleck (1996) model of compressible hydrodynamic turbulence. In...
Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration (2007)
We attempt to explain the non-thermal emission arising from galaxy clusters as a result of the re-acceleration of electrons by compressible turbulence induced by cluster mergers. In our model...
X-ray line emission produced in clump bow shocks (2007)
Cassinelli, Joe P., Ignace, R., Waldron, W., Cho, J., Murphy, N., Lazarian, A.
We summarize Chandra observations of the emission line profiles from 17 OB stars. The lines tend to be broad and unshifted. The forbidden/intercombination line ratios arising from Helium-like ions...
X-ray line emission produced in clump bow shocks (2007)
Cassinelli, Joe P., Ignace, R., Waldron, W., Cho, J., Murphy, N., Lazarian, A.
We summarize Chandra observations of the emission line profiles from 17 OB stars. The lines tend to be broad and unshifted. The forbidden/intercombination line ratios arising from Helium-like ions...
Velocity spectrum for HI at high latitudes (2006)
Chepurnov, A., Lazarian, A., Stanimirovic, S., Peek, J. E. G., Heiles, C.
In this paper we present results of the statistical analysis of high-latitude HI turbulence in the Milky Way. We have observed HI in the 21 cm line, obtained with the Arecibo L-Band Feed Array (ALFA)...
Turbulence is a key element of the dynamics of astrophysical fluids, including those of interstellar medium, clusters of galaxies and circumstellar regions. Turbulent motions induce Doppler shifts of...
Velocity coordinate spectrum: geometrical aspects of observations (2006)
We analyze a technique of obtaining turbulence power spectrum using spectral line data along the velocity coordinate, which we refer to as Velocity Coordinate Spectrum (VCS). We formalize geometrical...
A Comparative Study of Velocity Statistics of Hydrodynamic and Magnetohydrodynamic Turbulence (2006)
Hall, Nicholas, Kowal, G., Lazarian, A., Cho, Jungyeon
Turbulence in an incompressible fluid with and without a magnetic field as well as moderately compressible MHD turbulence are compared. For the magnetohydrodynamic (MHD) models the probability...
Polarization of Dust Emission in Clumpy Molecular Clouds and Cores (2006)
Bethell, T. J., Chepurnov, A., Lazarian, A., Kim, J.
Grain alignment theory has reached the stage where quantitative predictions of the degree of alignment and its variations with optical depth are possible. With the goal of studying the effect of...
Grain Alignment and Polarized Emission from Magnetized T Tauri Disks (2006)
The structure of magnetic fields within protostellar disks may be studied via polarimetry provided that grains are aligned in respect to magnetic field within the disks. We explore alignment of dust...
The relative population of the fine structure sublevels of an atom's ground state is affected by radiative transitions induced by an anisotropic radiation flux. This causes the alignment of atomic...
We show that atomic alignment presents a reliable way to study topology of astrophysical magnetic fields. The effect of atomic alignment arises from modulation of the relative population of the...
Turbulence Spectra from Doppler-shifted Spectral Lines (2006)
Turbulence is a key element of the dynamics of astrophysical fluids, including those of interstellar medium, clusters of galaxies and circumstellar regions. Turbulent motions induce Doppler shifts of...
Turbulence Effects at Small Scales (2006)
It is most natural to assume that mysterious Small Ionized and Neutral Structures (SINS) indiffuse ISM arise from turbulence. There are two obvious problem with such an explanation, however. First of...
Compressible MHD Turbulence: Mode Coupling, Anisotropies, and Scalings (2006)
Compressible MHD Turbulence: Mode Coupling, Anisotropies, and Scalings
Cascading of Fast-Mode Balanced and Imbalanced Turbulence (2006)
Suzuki, T. K., Lazarian, A., Beresnyak, A.
We study the cascading of fast MHD modes in magnetically dominated plasma by performing one-dimensional (1D) dynamical simulations. We find that the cascading becomes more efficient as an angle...
Intermittency of Magnetohydrodynamic Turbulence: Astrophysical Perspective (2006)
Intermittency is an essential property of astrophysical fluids, which demonstrate an extended inertial range. As intermittency violates self-similarity of motions, it gets impossible to naively...
Density Fluctuations in MHD Turbulence: Spectra, Intermittency and Topology (2006)
Kowal, G., Lazarian, A., Beresnyak, A.
We perform three-dimensional (3D) compressible MHD simulations over many dynamical times for an extended range of sonic and Alfven Mach numbers and analyze the statistics of 3D density and 2D column...
Enhancement and suppression of heat transfer by MHD turbulence (2006)
We study of the effect of turbulence on heat transfer within magnetized plasmas for energy injection velocities both larger and smaller that the Alfven speed. We find that in the latter regime the...
SINS of Viscosity Damped Turbulence (2006)
The problems with explaining the Small Ionized and Neutral Structures (SINS) appealing to turbulence stem from inefficiency of the Kolmogorov cascade in creating large fluctuations at sufficiently...
Intercluster medium is expected to be turbulent with turbulence being superAlfvenic at large scales. Magnetic fields substantially modify the turbulent cascade when the turbulence reaches the scales...
Grain Alignment, Polarization and Magnetic Fields (2006)
Aligned non-spherical dust particles polarize starlight passing through the dust cloud. They also emit polarized far infrared and sub-mm radiation. Substantial progress in understanding of grain...
Fast reconnection of magnetic fields in turbulent fluids (2006)
Fast reconnection of magnetic fields in turbulent fluids
MHD Turbulent Mixing Layers: Equilibrium Cooling Models (2006)
Esquivel, A., Benjamin, R. A., Lazarian, A., Cho, J., Leitner, S. N.
We present models of turbulent mixing at the boundaries between hot (T~10^{6-7} K) and warm material (T~10^4 K) in the interstellar medium, using a three-dimensional magnetohydrodynamical code, with...
Interstellar cloud structure: The statistics of centroid velocities (2006)
Ossenkopf, V., Esquivel, A., Lazarian, A., Stutzki, J.
The investigation of the statistical properties of maps of line centroids has been used for almost 50 years, but there is still no general agreement on their interpretation. We try to quantify which...
Studying Turbulence using Doppler-broadened lines: Velocity Coordinate Spectrum (2005)
We discuss a new technique for studying astrophysical turbulence that utilizes the statistics of Doppler-broadened spectral lines. The technique relates the power Velocity Coordinate Spectrum (VCS),...
Particle Acceleration by MHD Turbulence (2005)
Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for revisions in the picture of particle acceleration. We make use of the recently established scaling of slow and fast...
Cosmic ray transport in MHD turbulence (2005)
Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for revisions in the picture of cosmic ray transport. In this paper we use recently obtained scaling laws for MHD modes...
Turbulence Statistics from Spectral Line Observations (2005)
Turbulence is a crucial component of dynamics of astrophysical fluids dynamics, including those of ISM, clusters of galaxies and circumstellar regions. Doppler shifted spectral lines provide a unique...
MHD Turbulence: Properties of Alfven, Slow and Fast Modes (2005)
We summarise basic properties of MHD turbulence. First, MHD turbulence is not so messy as it is believed. In fact, the notion of strong non-linear coupling of compressible and incompressible motions...
Grain Alignment by Radiation in Dark Clouds and Cores (2005)
We study alignment of grains by radiative torques. We found steep rise of radiative torque efficiency as grain size increases. This allows larger grains that are known to exist within molecular...
Statistics of turbulence via polarimetry: alignment of grains and atoms (2005)
Most astrophysical fluids are turbulent and magnetized. Fluctuations of polarization provide a promising way to study astrophysical magnetic turbulence. We discuss polarization that arises from...
Astrophysical Implications of Turbulent Reconnection: from cosmic rays to star formation (2005)
Turbulent reconnection allows fast magnetic reconnection of astrophysical magnetic fields. This entails numerous astrophysical implications and opens new ways to approach long standing problems. I...
Collisionless Damping of Fast MHD Waves in Magneto-rotational Winds (2005)
Suzuki, T. K., Yan, H., Lazarian, A., Cassinelli, J. P.
We propose collisionless damping of fast MHD waves as an important mechanism for the heating and acceleration of winds from rotating stars. Stellar rotation causes magnetic field lines anchored at...
Density scaling and anisotropy in supersonic MHD turbulence (2005)
Beresnyak, A., Lazarian, A., Cho, J.
We study the statistics of density for supersonic turbulence in a medium with magnetic pressure larger than the gaseous pressure. This study is motivated by molecular cloud research. Our simulations...
Magnetically limited X-ray filaments in young SNR (2005)
Pohl, M., Yan, H., Lazarian, A.
We discuss the damping of strong magnetic turbulence downstream of the forward shock of young supernova remnants (SNR). We find that strong magnetic fields, that have been produced by the streaming...
Spurious contribution to CR scattering calculations (2004)
Shalchi, A., Yan, H., Lazarian, A.
The quasilinear theory for cosmic ray propagation is a well known and widely accepted theory. In this paper, we discuss the different contributions to the pitch-angle Fokker-Planck coefficient from...
Magnetic turbulence in compressible fluids (2004)
We present high resolution numerical simulations of compressible magnetohydrodynamic (MHD) turbulence. We concentrate on studies of spectra and anisotropy of velocity and density. We describe a...
Dust Dynamics in Compressible MHD Turbulence (2004)
Yan, Huirong, Lazarian, A., Draine, B. T.
We calculate the relative grain-grain motions arising from interstellar magnetohydrodynamic (MHD) turbulence. The MHD turbulence includes both fluid motions and magnetic fluctuations. While the fluid...
Cosmic Ray Scattering and Streaming in Compressible Magnetohydrodynamic Turbulence (2004)
Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for revisions in the picture of cosmic ray transport. In this paper we use recently obtained scaling laws for MHD modes...
Alignment of Dust in Molecular Clouds (2004)
Polarimetry is one of the most informative techniques of studying magnetic fields in molecular clouds. How reliable the interpretation of the polarization maps in terms of magnetic fields is the...
Scaling, Intermittency and Decay of MHD Turbulence (2004)
We discuss a few recent developments that are important for understanding of MHD turbulence. First, MHD turbulence is not so messy as it is usually believed. In fact, the notion of strong non-linear...
Obtaining Statistics of Turbulent Velocity from Astrophysical Spectral Line Data (2004)
Turbulence is a crucial component of dynamics of astrophysical fluids dynamics, including those of ISM, clusters of galaxies and circumstellar regions. Doppler shifted spectral lines provide a unique...
The Anisotropy of Electron MHD Turbulence (2004)
We present numerical studies of 3-dimensional electron magnetohydrodynamic (EMHD) turbulence. We investigate cascade timescale and anisotropy of freely decaying strong EMHD turbulence with zero...
Velocity Modification of Power Spectrum from Absorbing Medium (2004)
Quantitative description of the statistics of intensity fluctuations within spectral line data cubes introduced in our earlier work is extended to the absorbing media. A possibility of extracting 3D...
Velocity centroids as tracers of the turbulent velocity statistics (2004)
We use the results of magnetohydrodynamic (MHD) simulations to emulate spectroscopic observations and use maps of centroids to study their statistics. In order to assess under which circumstances the...
Translational Velocities and Rotational Rates of Interstellar Dust Grains (2003)
Interstellar dust grains exhibit complex dynamics which is essential for understanding many key interstellar processes that involve dust, including grain alignment, grain growth, grain shattering...
Basic Properties of Compressible MHD Turbulence: Implications for Molecular Clouds (2003)
Recent advances in understanding of the basic properties of compressible Magnetohydrodynamic (MHD) turbulence call for revisions of some of the generally accepted concepts. First, MHD turbulence is...
Cosmic Ray Scattering by Compressible Magnetohydrodynamic Turbulence (2003)
Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for substantial revisions in the picture of cosmic ray transport. In this paper we use recently obtained scaling laws for...
Grain Alignment in Molecular Clouds (2003)
One of the most informative techniques of studying magnetic fields in molecular clouds is based on the use of starlight polarization and polarized emission arising from aligned dust. How reliable the...
Magnetic Field Structure and Stochastic Reconnection in a Partially Ionized Gas (2003)
Lazarian, A., Vishniac, E. T., Cho, J.
We consider stochastic reconnection in a magnetized, partially ionized medium. Stochastic reconnection is a generic effect, due to field line wandering, in which the speed of reconnection is...
We here propose that the large scale superluminal ejections observed in the galactic microquasar GRS 1915+105 during radio flare events are produced by violent magnetic reconnection episodes in the...
Microwave Emission from Aligned Dust (2003)
Polarized microwave emission from dust is an important foreground that may contaminate polarized CMB studies unless carefully accounted for. We discuss potential difficulties associated with this...
Angular Spectra of Polarized Galactic Foregrounds (2003)
It is believed that magnetic field lines are twisted and bend by turbulent motions in the Galaxy. Therefore, both Galactic synchrotron emission and thermal emission from dust reflects statistics of...
Ordinary and Viscosity-Damped MHD Turbulence (2003)
Cho, Jungyeon, Lazarian, A., Vishniac, Ethan T.
We compare the properties of ordinary strong magnetohydrodynamic (MHD) turbulence in a strongly magnetized medium with the recently discovered viscosity-damped regime. We focus on energy spectra,...
Statistics of Velocity from Spectral Data: Modified Velocity Centroids (2003)
We address the problem of studying interstellar turbulence using spectral line data. We find a criterion when the velocity centroids may provide trustworthy velocity statistics. To enhance the scope...
Thermal Conduction in Magnetized Turbulent Gas (2003)
Cho, J., Lazarian, A., Honein, A., Knaepen, B., Kassinos, S., Moin, P.
Using numerical methods, we systematically study in the framework of ideal MHD the effect of magnetic fields on heat transfer within a turbulent gas. We measure the rates of passive scalar diffusion...
Magnetic Reconnection and Turbulent Mixing: From ISM to Clusters of Galaxies (2003)
Magnetic reconnection, or the ability of the magnetic field lines that are frozen in plasma to change their topology, is a fundamental problem of magnetohydrodynamics (MHD). We briefly examine the...
Generation of Compressible Modes in MHD Turbulence (2003)
Astrophysical turbulence is magnetohydrodynamic (MHD) in its nature. We discuss fundamental properties of MHD turbulence. In particular, we discuss the generation of compressible MHD waves by...
Physics of Gamma-Ray Bursts: Turbulence, Energy Transfer and Reconnection (2003)
Lazarian, A., Petrosian, V., Yan, H., Cho, J.
Understanding of the nature of gamma-ray bursts (GRBs) is one of the challenging problem facing the astrophysics community. The field of gamma ray bursts is a rapidly developing one and we expect...
We present numerical simulations and explore scalings and anisotropy of compressible magnetohydrodynamic (MHD) turbulence. Our study covers both gas pressure dominated (high beta) and magnetically...
GLIMPSE. I. An SIRTF Legacy Project to Map the Inner Galaxy (2003)
Benjamin, RA, Churchwell, E, Babler, BL, Bania, TM, Clemens, DP, Cohen, M, ...
Grain Acceleration by MHD Turbulence: Gyroresonance Mechanism (2002)
We discuss a new mechanism of dust acceleration that acts in a turbulent magnetized medium. The magnetohydrodynamic (MHD) turbulence includes both fluid motions and magnetic fluctuations. We show...
Compressible MHD Turbulence: Mode Coupling, Anisotropies and Scalings (2002)
Compressible turbulence, especially the magnetized version of it, traditionally has a bad reputation with researchers. However, recent progress in theoretical understanding of incompressible MHD as...
The Properties of Compressible MHD and Cosmic Ray Transport (2002)
Lazarian, A., Cho, Jungyeon, Yan, Huirong
Turbulence is the most common state of astrophysical flows. In typical astrophysical fluids, turbulence is accompanied by strong magnetic fields, which has a large impact on the dynamics of the...
Polarized Foreground Emission from Dust: Grain Alignment and MHD Turbulence (2002)
Aligned grains present a foreground for cosmic microwave emission studies. We review basic physical processes involved in grain alignment and discuss the niches for different alignment mechanisms. We...
Esquivel, Alejandro, Lazarian, A., Pogosyan, D., Cho, Jungyeon
In a previous work Lazarian and Pogosyan suggested a technique to extract velocity and density statistics, of interstellar turbulence, by means of analysing statistics of spectral line data cubes. In...
Magnetic Fields via Polarimetry: Progress of Grain Alignment Theory (2002)
Most astrophysical systems, e.g. stellar winds, the diffuse interstellar medium, molecular clouds, are magnetized with magnetic fields that influence almost all of their properties. One of the most...
Efroimsky, Michael, Lazarian, A., Sidorenko, Vladislav
Neutron stars, asteroids, comets, cosmic-dust granules, spacecraft, as well as whatever other freely spinning body dissipate energy when they rotate about any axis different from principal. We...
Problems and Progress in Astrophysical Dynamos (2002)
Vishniac, E. T., Lazarian, A., Cho, J.
Astrophysical objects with negligible resistivity are often threaded by large scale magnetic fields. The generation of these fields is somewhat mysterious, since a magnetic field in a perfectly...
Dust Motions Driven by MHD Turbulence (2002)
We discuss the relative grain motions due to MHD turbulence in interstellar medium. It has been known for decades that turbulent drag is an efficient way to induce grain relative motions. However,...
Scattering of Cosmic Rays by Magnetohydrodynamic Interstellar Turbulence (2002)
Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for substantial revisions in our understanding of cosmic ray transport. In this paper we use gyroresonance recently...
Compressible Sub-Alfvenic MHD turbulence in Low-beta Plasmas (2002)
We present a model for compressible sub-Alfvenic isothermal magnetohydrodynamic (MHD) turbulence in low-beta plasmas and numerically test it. We separate MHD fluctuations into 3 distinct families -...
MHD Turbulence as a Foreground for CMB Studies (2002)
Measurements of intensity and polarization of diffuse Galactic synchrotron emission as well as starlight polarization reveal power law spectra of fluctuations. We show that these fluctuations can...
MHD Turbulence: Scaling Laws and Astrophysical Implications (2002)
Cho, Jungyeon, Lazarian, A., Vishniac, Ethan
Turbulence is the most common state of astrophysical flows. In typical astrophysical fluids, turbulence is accompanied by strong magnetic fields, which has a large impact on the dynamics of the...
Grain Dynamics In Magnetized Interstellar Gas (2001)
Interstellar medium is turbulent and this induces relative motions of dust grains. We calculate relative velocities of charged grains in a partially ionized magnetized gas. We account for anisotropy...
Quest for HI Turbulence Statistics: New Techniques (2001)
Lazarian, A., Pogosyan, D., Esquivel, Alejandro
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...
New Regime of MHD Turbulence: Cascade Below Viscous Cutoff (2001)
Cho, Jungyeon, Lazarian, A., Vishniac, Ethan
In astrophysical situations, e.g. in the interstellar medium (ISM), neutrals can provide viscous damping on scales much larger than the magnetic diffusion scale. Through numerical simulations, we...
Polarized Microwave Emission from Dust (2001)
Polarized emission from dust is an important foreground that can hinder the progress in polarized CMB studies unless carefully accounted for. We discuss potential difficulties associated with the...
Velocity and density spectra of the Small Magellanic Cloud (2001)
Stanimirović, S., Lazarian, A.
This paper reports results on the statistical analysis of HI turbulence in the Small Magellanic Cloud (SMC). We use 21 cm channel maps, obtained with the Australia Telescope Compact Array and the...
Polarized Microwave Radiation from Dust (2000)
Observations of cosmic microwave background in the range 10-90 GHz have revealed an anomalous foreground component well correlated with 12 \mum, 60 \mum and 100 \mum emission from interstellar dust....
Resonance Paramagnetic Relaxation and Alignment of Small Grains (2000)
We show that the energy-level splitting arising from grain rotation ensures that paramagnetic dissipation acts at its maximum rate, i.e., the conditions for paramagnetic resonance are automatically...
We here investigate the possibility that the ultra-high energy cosmic ray (UHECR) events observed above the GZK limit are mostly protons accelerated in reconnection sites just above the magnetosphere...
Ultra-High-Energy Cosmic Ray Acceleration by Magnetic Reconnection in Newborn Pulsars (2000)
We here investigate the possibility that the ultra-high energy cosmic ray (UHECR) events observed above the GZK limit are mostly protons accelerated in econnection sites just above the magnetosphere...
Fast Turbulent Reconnection (2000)
Reconnection is the process by which magnetic fields in a conducting fluid change their topology. This process is essential for understanding a wide variety of astrophysical processes, including...
Fast reconnection of magnetic fields in turbulent fluids (2000)
Reconnection is the process by which magnetic elds in a conducting uid change their topology. This process is essential for understanding a wide variety of astrophysical processes, including stellar...
Statistics of Turbulence from Spectral-Line Data Cubes (1999)
Emission in spectral lines can provide unique information on interstellar turbulence. Doppler shifts due to supersonic motions contain information on turbulent velocity field which is otherwise...
Nuclear Spin Relaxation within Interstellar Grains (1999)
We identify a new mechanism of internal dissipation of rotational kinetic energy in spinning dust grains, arising from the reorientation of nuclear angular momentum, e.g., spins of protons. Grain...
Microwave Emission from Galactic Dust Grains (1999)
Observations of the cosmic microwave background have revealed a component of 10-60 GHz emission from the Galaxy which correlates with 100-140um emission from interstellar dust but has an intensity...
Polarized Foreground from Thermal Dust Emission (1999)
In this review, we intend to present the current knowledge of the polarized emission from thermal dust in our Galaxy. We show different methods to estimate the spatial distribution statistics of this...
Velocity Modification of HI Power Spectrum (1999)
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)...
Thermal Flipping and Thermal Trapping -- New Elements in Dust Grain Dynamics (1999)
Since the classical work by Purcell (1979) it has been generally accepted that most interstellar grains rotate suprathermally. Suprathermally rotating grains would be nearly perfectly aligned with...
Magnetic Dipole Microwave Emission from Dust Grains (1999)
Draine A. Lazarian, B. T. Draine, A. Lazarian
Thermal fluctuations in the magnetization of interstellar grains will produce magnetic dipole emission at ¸ ! 100 GHz. We show how to calculate absorption and emission from small particles composed...
Davis-Greenstein alignment of oblate spheroidal grains (1998)
We present extensive calculations on the efficiency of grain alignment by the Davis-Greenstein mechanism. We model the grains as oblate spheroids with arbitrary axis ratios. Our description of the...
Reconnection in a Weakly Stochastic Field (1998)
We examine the effect of weak, small scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale...
Inelastic Dissipation in a Freely Rotating Body. Application to Cosmic-Dust Alignment (1998)
Motivated by a recent study by Lazarian and Draine, which showed that a high degree of grain alignment of the paramagnetic dust is achievable if the rates of internal relaxation are controlled by the...
Inelastic Dissipation in Wobbling Asteroids and Comets (1998)
Efroimsky, Michael, Lazarian, A.
Asteroids and comets dissipate energy when they rotate about the axis different from the axis of the maximal moment of inertia. We show that the most efficient internal relaxation happens at the...
Turbulent Cooling Flows in Molecular Clouds (1998)
We propose that inward, subsonic flows arise from the local dissipation of turbulent motions in molecular clouds. Such "turbulent cooling flows" may account for recent observations of spatially...
Magnetic Dipole Microwave Emission from Dust Grains (1998)
Thermal fluctuations in the magnetization of interstellar grains will produce magnetic dipole emission at frequencies below ~100 GHz. We show how to calculate absorption and emission from small...
Reconnection via the Tearing Instability (1998)
Lazarian, A., Vishniac, Ethan T.
We discuss the role of tearing instabilities in magnetic reconnection. In three dimensions this instability leads to the formation of strong Alfvenic waves that remove plasma efficiently from the...
Turbulence in Atomic Hydrogen (1998)
Understanding the properties of interstellar turbulence is a great intellectual challenge and the urge to solve this problem is partially motivated by a necessity to explain the star formation...
Electric Dipole Radiation from Spinning Dust Grains (1998)
We discuss the rotational excitation of small interstellar grains and the resulting electric dipole radiation from spinning dust. Attention is given to excitation and damping of rotation by:...
astro-ph/9811044 3 Nov 1998 (1998)
The Astrophysical, P. C. Myers, A. Lazarian
We propose that inward, subsonic flows arise from the local dissipation of turbulent motions in molecular clouds. Such "turbulent cooling flows" may account for recent observations of...
Reconnection in the ISM (1997)
Vishniac, Ethan T., Lazarian, A.
We discuss the role of ambipolar diffusion for simple reconnection in a partially ionized gas, following the reconnection geometry of Parker and Sweet. When the recombination time is short the...
Diffuse Galactic Emission from Spinning Dust Grains (1997)
Spinning interstellar dust grains produce detectable rotational emission in the 10-100 GHz frequency range. We calculate the emission spectrum, and show that this emission can account for the...
On the efficiency of grain alignment in dark clouds (1997)
Lazarian, A., Goodman, Alyssa A., Myers, Philip C.
A quantitative analysis of grain alignment in the filamentary dark cloud L1755 in Ophiuchus is presented. We show, that the observed decrease of the polarization to extinction ratio for the inner...
Cosmic rays and grain alignment (1997)
The recent detection of interstellar polarization in the solid CO feature near 4.67 micron shows that CO-mantled grains can be aligned in cold molecular clouds. These observations conflict with a...
Gold alignment & internal dissipation (1997)
The measures of mechanical alignment were obtained for both prolate and oblate grains when their temperature is comparable with grain kinetic energy devided by k, the Boltzmann constant. For such...
Paramagnetic alignment of thermally rotating dust (1997)
Paramagnetic alignment of thermally rotating oblate dust grains is studied analytically for finite ratios of grain to gas temperatures. For such ratios, the alignment of angular momentum J in respect...
Barnett Relaxation in Thermally-Rotating Grains (1997)
We present an exact formulation of the physics of Barnett relaxation. Our formulation is based on a realistic kinetic model of the relaxation mechanism which includes the alignment of the grain...
Disorientation of Suprathermally Rotating Grains and Grain Alignment Problem (1996)
We discuss the dynamics of dust grains subjected to uncompensated torques arising from H_2 formation. In particular, we discuss grain dynamics when a grain spins down and goes through a...
Alignment of suprathermally rotating grains (1995)
It is shown, that mechanical alignment can be efficient for suprathermally rotating grains, provided that they drift with supersonic velocities. Such a drift should be widely spread due to both...
Occlusion Effects and the Distribution of Interstellar Cloud Sizes and Masses (1995)
The frequency distributions of sizes of ``clouds" and ``clumps" within clouds are significantly flatter for extinction surveys than for CO spectral line surveys, even for comparable size ranges. A...
Davis-Greenstein alignment of non-spherical grains (1995)
Paramagnetic alignment of non-spherical dust grains rotating at thermal velocities is studied. The analytical solution is found for the alignment measure of oblate grains. Perturbative approach is...
Mechanical alignment of suprathermally rotating grains (1995)
It is shown that mechanical alignment of grains can be efficient for grains rotating suprathermally, i.e. with kinetic energy substantially exceeding $k$ (the Boltzmann constant) over any temperature...
Paramagnetic alignment of fractal grains (1994)
Paramagnetic alignment of fractal suprathermally rotating grains is discussed. It is shown that if the concentration of H$_{2}$formation sites is low and resurfacing is active, fractal structure of...