thermal emission

(thermal radiation; thermal bremsstrahlung) Electromagnetic radiation resulting from interactions between electrons and atoms or molecules in a hot dense medium. The term usually refers to thermal emission from ionized gas (but see also thermal black-body radiation). Free electrons in the ionized gas radiate when they are deflected in passing near protons. The electrons are unbound to a nucleus before and after each encounter and the radiation is therefore also known as free-free emission. The radiation has a continuous spectrum, which at low frequencies has the spectral index, α, of a thermal black-body radiator, i.e. S ∝ ν^–α; α = –2 where S is the flux density and ν the frequency. At higher frequencies the spectrum flattens to a spectral index of α = 0. The emission measure of an ionized region of length l containing a density n _e of free electrons is given by EM = ^l ₀ n _e ² ds where ds is an element of the path through the region. Compare nonthermal emission.

thermal emission

thermal emission

thermal emission

thermal emission

Synonyms for thermal emission

noun the emission of electrons from very hot substances

Synonyms

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