Page 34 - 83 basic knowledge of astronomy

Figure 26: Interpretation of the spectrum of the Orion Nebula. Left panel is
from Kraus (1986).

11 Synchrotron Radiation

Synchrotron radiation is a typical example of non-thermal radiation caused
by the high–speed (“relativistic”) electrons in their accelerated helical motion
in a magnetic field. Historically, synchrotron radiation was first discovered in
1948, as the light emitted by a particle accelerator called the “Synchrotron”.
Synchrotron radiation is dominant in a variety of astronomical objects, in-
cluding “Active Galactic Nuclei” (AGNs), Supernova Remnants (SNRs), and
solar flares (see Figure 27 as an example).

11.1 Non–Relativistic Case

In the non–relativistic case, the analog of synchrotron radiation is known as
“cyclotron” or “gyro–synchrotron” radiation. In this case, the balance of the
Lorentz force and the centrifugal force
m 0 v 2
e(v ⊥ × B) = ⊥ ,
r
gives rise to “Larmor Precession” with “gyro–frequency” ν G :

1 eB
v ⊥
ν G = = ,
2πr 2π m 0
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