Description of a Relativistic Plasma
Relativistic plasmas occur in several astrophysical environments, such as galactic jets; they are also created in laboratory experiments, usually by means of high intensity lasers. Relativistic gyration is the same as the non-relativistic case, except that the gyrofrequency is modified by the relativistic mass increase. The relativistic treatment differs in essentially two ways: first, some care is needed to define a magnetized plasma in the relativistic case; and second, the unit vector needs to be replaced by a covariant quantity, in order to give invariant meaning to the terms "parallel" and "perpendicular". A magnetized plasma must satisfy two conditions: the gradient scale lengths of the fluid variables must exceed the gyroradius, and, the parallel electric field must be relatively small. Electromagnetic radiation plays an important role in many relativistic plasmas. Furthermore, in the ultrarelativistic case, particle creation must be taken into account.