radiative transfer
The transfer of radiation (energy) leaving one object and being absorbed by another.
Examples of radiative transfer in the following topics:
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Introduction
- We are going to set the stage for a deeper look at astrophysical sources of radiation by defining the important concepts of radiative transfer, thermal radiation and radiative diffusion.
- Upon these assumptions the field of radiative transfer is built.
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The Radiative Transfer Equation
- Once we know and for the system of interest, it is straightforward to solve the equations of radiative transfer.
- The result for pure absorption inspires us to look at the radiative transfer equation again.
- Using this definition we get the following equation of radiative transfer,
- It allows a formal solution of the transfer equation.
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Eddington Approximation
- The source function is isotropic, so let's average the radiative transfer equation over direction to yield
- Let's also average the radiative transfer equation times over direction to yield
- This is sometimes called the radiative diffusion equation.
- If you know the temperature structure of the material you can solve the equation for the mean intensity and then you know the source function explicitly and you can use the formal solution to the radiative transfer equation to get the radiation field.
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Transformation of Radiative Transfer
- The equations of radiative transfer follow the intensity of the radiation field.We would like to understand how this and other radiative transfer quantities transform relativistically.
- Because the source function appears in the equations of radiative transfer as , must have the same transformation properties as , i.e.
- These relations allow us to calculate the radiative transfer through a medium in whichever frame is convenient.
- We could calculate the source function and absorption in the rest-frame of the material and the radiative transfer in the "lab'' frame.
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Greenhouse Gases and Global Warming
- Radiation is a natural process of heat transfer; everything is constantly radiating heat.
- The greenhouse effect is a phenomenon of radiative transfer, the process by which the energy of light waves is exchanged in matter.
- Radiative transfer dictates what energy is reflected, absorbed, and emitted .
- The radiative transfer properties of atmospheric chemicals depend on the energy of the radiation (both for absorption and emission), and those properties are unique to each chemical.
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Modelling the Stress
- We can combine the -prescription with vertical radiative transfer to obtain an estimate of the central density and temperature of the disk.
- By combining the previous equation with with vertical radiative transfer, we obtain
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Blackbody Radiation
- Second if a material is emitting thermal radiation one can obtain a simple expression of the radiative transfer equation (see the problems).
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Thermodynamics
- The brightness temperature has several nice properties.For one thing it has units of Kelvin rather than something clumsy.Second if a material is emitting thermal radiation one can obtain a simple expression of the radiative transfer equation (see the problems).
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Blackbody Temperatures
- Second if a material is emitting thermal radiation one can obtain a simple expression of the radiative transfer equation (see the problems).
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Overview of Heat
- This module defines and explores heat transfer, its effects, and the methods by which heat is transferred.
- It is something which may be transferred from one body to another.
- After defining and quantifying heat transfer and its effects on physical systems, we will discuss the methods by which heat is transferred.
- So many processes involve heat transfer, so that it is hard to imagine a situation where no heat transfer occurs.
- (a) The chilling effect of a clear breezy night is produced by the wind and by radiative heat transfer to cold outer space.