The electromagnetic (EM) process are always related to
photons because they are the particles to carry energy and
momentum in electromagnetic interactions. Therefore, some
of the EM reactions would GENERATE photons, such as
pair annihilation
, the inverse
process of the pair creation. Electrons are also
producing photons by interacting with **magnetic** field,
which is called synchrotron radiation, the representative
radiation process that can be described in the standard context
of the classical electromagnetic theory.

Now let us derive the radiation intensity, *i.e.*
the radiated energy per unit time
.
First we expand the treatment of the dipole radiation
given by Eq. 8
to the super-relativistic condition that particles are moving
almost at speed of light.
The dipole is related to acceleration
by
and Eq. 8
gives the total radiation intensity as

(37) |

since

(39) |

The equation of motion in and is

(41) |

In the uniform field, an electron's movement
is characterized by the synchrotron frequency

(43) |

(44) |

(45) |

where is the energy density of magnetic field. When a particle moving in is an electron, is set to in the above equation.

Energies of the radiated photons are narrowly distributed
around

2002-07-18