Unformatted text preview: 3.6.2 Thermal bremsstrahlung
Thermal electrons (i.e. electrons with Maxwell-Boltzman distributions) moving near positive ions (e.g. H nuclei). Coulomb interactions cause the acceleration.
e p Radiation is less intense; almost unpolarized; very at spectrum in radio, \thermal" in X-ray (Planck-like).
typical radio: log Iν ν −0.1
e−ν/ν0 ν 2.5
log ν ν Usually associated with hot gas: X-rays from clusters of galaxies; HII regions; surface of sun. Bremsstrahlung is usually associated with hot gas: X-rays from clusters
of galaxies, HII regions, or the surface of the Sun, e.g.
Synchrotron radiations and thermal bremsstrahlung are two of the common continuum emission mechanisms of gas. (Solids, e.g. surface of the
Earth, are dierent.) 3.6.3 Line emission from atoms
Electrons jumping from higher to lower levels in atoms emit excess energy
as line radiation. The distribution of the lines in frequency and intensity are
characterisic of the chemical element involved.
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