Reciprocity relations in radiative transfer by spherical clouds.
Abstract
Time reversal i.e., the replacement of sources by detectors and conversely, leads in any configuration of light scattering particles to mutually reciprocal problems, which have essentially the same solution. This principle is applied to a set of problems with spherically symmetric radiation fields in a homogeneous spherical cloud. Internal or external sources and detectors are permitted. The individual scatterers may have arbitrary albedo α and an arbitrary phase function. The optical depth R along the radius of the cloud is also arbitrary. Each function belonging to a particular source-detector combination is defined as a quantity measurable in a fictitious experiment. The principle of detailed balancing then is used to establish their reciprocity relations. Additional inter-relations are based on the conservation of energy and on volume integration. The relations permit surprising checks on analytical, numerical, or graphical results cited from papers treating very diverse problems. A set of examples for isotropic scattering is examined in detail and shows excellent agreement throughout. Among the possible extensions is a theorem on a homogeneous cloud of arbitrary shape with arbitrary phase function; this theorem relates the radiation field arising from uniform external illumination to the radiation field arising from uniformly embedded sources.
- Publication:
-
Journal of Quantitative Spectroscopy and Radiative Transfer
- Pub Date:
- January 2000
- DOI:
- 10.1016/S0022-4073(99)00110-7
- Bibcode:
- 2000JQSRT..64..151V
- Keywords:
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- Radiative Transfer: Scattering;
- Radiative Transfer: Clouds