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Radiative transfer

About: Radiative transfer is a research topic. Over the lifetime, 43287 publications have been published within this topic receiving 1176539 citations.


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TL;DR: In this paper, it was shown that radiative torque on an irregular grain geometry can play an important dynamical role in spinup of interstellar dust grains, resulting in rotation rates which may exceed even those expected from H 2 formation on the grain surface.
Abstract: 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 irregular grain geometry, and three different grain sizes It is shown that radiative torques can play an important dynamical role in spinup of interstellar dust grains, resulting in rotation rates which may exceed even those expected from H_2 formation on the grain surface Because the radiative torque on an interstellar grain is determined by the overall grain geometry rather than merely the state of the grain surface, the resulting superthermal rotation is expected to be long-lived By itself, long-lived superthermal rotation would permit grain alignment by normal paramagnetic dissipation on the "Davis-Greenstein" timescale However, radiative torques arising from anisotropy of the starlight background can act directly to alter the grain alignment on much shorter timescales, and are therefore central to the process of interstellar grain alignment Radiative torques depend strongly on the grain size, measured by a_eff, the radius of a sphere of equal volume In diffuse clouds, radiative torques dominate the torques due to H2 formation for a_eff=02micron grains, but are relatively unimportant for a_eff 01 micron grains in diffuse clouds are aligned, while there is little alignment of a_eff < 005 micron grains We show that radiative torques are ineffective at producing superthermal rotation within quiescent dark clouds, but can be very effective in star-forming regions such as the M17 molecular cloud

342 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of a thermal radiative component on the observable spectrum was analyzed, assuming that the observable effects are due to a dissipation process occurring below or near the thermal photosphere.
Abstract: A thermal radiative component is likely to accompany the first stages of the prompt emission of gamma-ray bursts (GRBs) and X-ray flashes (XRFs) We analyze the effect of such a component on the observable spectrum, assuming that the observable effects are due to a dissipation process occurring below or near the thermal photosphere We consider both the internal shock model and a "slow heating" model as possible dissipation mechanisms For comparable energy densities in the thermal and leptonic components, the dominant emission mechanism is Compton scattering This leads to a nearly flat energy spectrum (νFν ∝ ν0) above the thermal peak at ≈10-100 keV and below 10-100 MeV, for a wide range of optical depths 003 τγe 100, regardless of the details of the dissipation mechanism or the strength of the magnetic field At lower energies steep slopes are expected, while above 100 MeV the spectrum depends on the details of the dissipation process For higher values of the optical depth, a Wien peak is formed at 100 keV-1 MeV, and no higher energy component exists For any value of τγe, the number of pairs produced does not exceed the baryon-related electrons by a factor of larger than a few We conclude that dissipation near the thermal photosphere can naturally explain both the steep slopes observed at low energies and a flat spectrum above 10 keV, thus providing an alternative scenario to the optically thin synchrotron-SSC model

339 citations

Journal ArticleDOI
TL;DR: A review of the various methods used to compute both the fluxes and the rate of heating and cooling due to atmospheric radiation for use in numerical models of atmospheric circulation is presented in this paper.
Abstract: This paper presents a review of the various methods used to compute both the fluxes and the rate of heating and/or cooling due to atmospheric radiation for use in numerical models of atmospheric circulation. The paper does not follow, step by step, the solution to the relevant radiative transfer problem but rather concentrates on providing the reader with the physical basis underlying the various methods. The paper discusses, separately, the various parameterizations for the absorptions by water vapor, carbon dioxide and ozone and for the scattering and absorption associated with cloud (and hazes) and also provides some indication of their accuracy.

338 citations

Journal ArticleDOI
TL;DR: In this paper, the radiative heat transfer between two semi-infinite bodies at subwavelength scale was studied and it was shown that this transfer can be enhanced by several orders of magnitude when the surfaces support resonant surface waves.
Abstract: We study in this article the radiative heat transfer between two semi-infinite bodies at subwavelength scale. We show that this transfer can be enhanced by several orders of magnitude when the surfaces support resonant surface waves. In these conditions, we show that the transfer is almost monochromatic.

336 citations

Journal ArticleDOI
TL;DR: In this paper, a 1D radiative transfer model of the envelopes of a sample of 18 low-mass protostars and pre-stellar cores with the aim of setting up realistic physical models, for use in a chemical description of the sources.
Abstract: We present 1D radiative transfer modelling of the envelopes of a sample of 18 low-mass protostars and pre-stellar cores with the aim of setting up realistic physical models, for use in a chemical description of the sources. The density and temperature proles of the envelopes are constrained from their radial proles obtained from SCUBA maps at 450 and 850 m and from measurements of the source fluxes ranging from 60 mt o 1.3 mm. The densities of the envelopes within 10 000 AU can be described by single power-laws / r for the class 0 and I sources with ranging from 1.3 to 1.9, with typical uncertainties of0.2. Four sources have flatter proles, either due to asymmetries or to the presence of an outer constant density region. No signicant dierence is found between class 0 and I sources. The power-law ts fail for the pre-stellar cores, supporting recent results that such cores do not have a central source of heating. The derived physical models are used as input for Monte Carlo modelling of submillimeter C 18 Oa nd C 17 O emission. It is found that class I objects typically show CO abundances close to those found in local molecular clouds, but that class 0 sources and pre-stellar cores show lower abundances by almost an order of magnitude implying that signicant depletion occurs for the early phases of star formation. While the 2{1 and 3{2 isotopic lines can be tted using a constant fractional CO abundance throughout the envelope, the 1{0 lines are signicantly underestimated, possibly due to contribution of ambient molecular cloud material to the observed emission. The dierence between the class 0 and I objects may be related to the properties of the CO ices.

336 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,706
20223,291
20211,335
20201,335
20191,429
20181,409