Unformatted text preview: 3.6 Radiation emission mechanisms brie
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 classied 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
appear log v Radio emission; traces very energetic regions. 57 may bend/break
at high frequency. ...
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