ay45c3-page33 - 3.6 Radiation emission mechanisms brie y...

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Unformatted text preview: 3.6 Radiation emission mechanisms brie y described Black body radiation is radiation that has come to thermal equilibrium and lost the memory of its original \creation." Sometimes, however, we are able to see photons directly as produced by the underlying microscopic processes. These need not have a Planck spectrum. What, microscopically, causes the radiation we see? The direct cause is always the same: acceleration of a charge creates radiation. The radiation is generally classi ed according to what causes the acceleration. We will list here three of the most important mechanisms. (You will learn much more about this in Astronomy 150.) 3.6.1 Synchrotron radiation Relativistic electrons being accelerated by magnetic elds (moving in helical patterns around eld lines): radiation emitted B e- Radiation is intense; often highly polarized; usually power-law spectrum. log I v I v is proportional to v - α α ~ 0.5 but may be ~0 or ~2! cut-off at low frequency may appear log v Radio emission; traces very energetic regions. 57 may bend/break at high frequency. ...
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This note was uploaded on 12/29/2011 for the course AST 350 taught by Professor Dion during the Fall '09 term at SUNY Stony Brook.

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