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Interstellar dust grains are non-spherical and, in some environments, partially aligned along the direction of the interstellar magnetic field. Numerous alignment theories have been proposed, all of which examine the grain rotational…

Astrophysics of Galaxies · Physics 2021-03-15 Joseph C. Weingartner , Erald Kolasi , Cameron Woods

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 ``crossover''. As first pointed out by Spitzer &…

Astrophysics · Physics 2009-10-28 A. Lazarian , B. T. Draine

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 etc. Grain rotational and translational…

Astrophysics · Physics 2007-05-23 A. Lazarian , Huirong Yan

In the previous papers in this series, we found that radiative torques can play a major role in the alignment of grains with the interstellar magnetic field. Since the radiative torques can drive the grains to suprathermal rotational…

Astrophysics · Physics 2009-11-07 Joseph C. Weingartner , B. T. Draine

In interstellar dust grains, internal processes dissipate rotational kinetic energy. The dissipation is accompanied by thermal fluctuations, which transfer energy from the vibrational modes to rotation. Together, these processes are known…

Astrophysics · Physics 2008-12-18 Joseph C. Weingartner

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 Alfv\'{e}nic waves and ambipolar diffusion.…

Astrophysics · Physics 2015-06-24 A. Lazarian

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 in the system. The paper studies…

Astrophysics · Physics 2009-10-28 A. Lazarian

Radiative torques on irregular dust grains, in addition to producing superthermal rotation, play a direct dynamical role in the alignment of interstellar dust with the local magnetic field. The equations governing the orientation of…

Astrophysics · Physics 2009-10-28 B. T. Draine , Joseph C. Weingartner

Several mechanisms have been proposed to explain the alignment of grains with the interstellar magnetic field, including paramagnetic dissipation, radiative torques, and supersonic gas-grain streaming. These must compete with disaligning…

Astrophysics · Physics 2008-11-26 Joseph C. Weingartner

A significant fraction of main sequence stars observed interferometrically in the near infrared have slightly extended components that have been attributed to very hot dust. To match the spectrum appears to require the presence of large…

Earth and Planetary Astrophysics · Physics 2016-01-13 George H. Rieke , Andras Gaspar , Nicholas P. Ballering

Irregular dust grains are subject to radiative torques when irradiated by interstellar starlight. It is shown how these radiative torques may be calculated using the discrete dipole approximation. Calculations are carried out for one…

Astrophysics · Physics 2009-10-28 B. T. Draine , Joseph C. Weingartner

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 grains enhances their alignment. Studying…

Astrophysics · Physics 2007-05-23 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) magnetic relaxation, (2) mechanical processes,…

Astrophysics · Physics 2007-05-23 Lazarian A

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 issue that the grain alignment theory…

Astrophysics · Physics 2016-08-30 A. Lazarian , J. Cho

This paper provides a quantitative account of a recently introduced mechanism of mechanical alignment of suprathermally rotating grains. These rapidly rotating grains are essentially not susceptible to random torques arising from gas-grain…

Astrophysics · Physics 2009-10-28 Alex Lazarian , Michael Efroimsky

Barnett relaxation, first described by Purcell in 1979, appears to play a major role in the alignment of grains with the interstellar magnetic field. In 1999, Lazarian and Draine proposed that Barnett relaxation and its relative, nuclear…

Astrophysics of Galaxies · Physics 2017-08-16 Erald Kolasi , Joseph C. Weingartner

In protoplanetary disks, the distribution and abundance of small (sub)micron grains are important for a range of physical and chemical processes. For example, they dominate the optical depth at short wavelengths and their surfaces are the…

Earth and Planetary Astrophysics · Physics 2016-05-25 Sebastiaan Krijt , Fred J. Ciesla

Grain surfaces play a central role in the formation and desorption of molecules in space. To form molecules on a grain surface, adsorbed species trapped in binding sites must be mobile and migrate to adjacent sites. Thermal hopping is a…

Astrophysics of Galaxies · Physics 2019-10-29 Thiem Hoang

The recent discovery of hot dust grains in the vicinity of main-sequence stars has become a hot issue among the scientific community of debris disks. Hot grains must have been enormously accumulated near their sublimation zones, but it is a…

Earth and Planetary Astrophysics · Physics 2018-08-13 Hiroshi Kimura , Masanobu Kunitomo , Takeru K. Suzuki , Jan Robrade , Philippe Thebault , Ikuyuki Mitsuishi

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 rotation induces magnetization of the…

Astrophysics · Physics 2010-10-27 A. Lazarian , B. T. Draine
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