  Thermal Doppler broadening of spectral profiles for particle populations in
the absence or presence of potential fields are described by kappa
distributions. The kappa distribution provides a replacement for the
Maxwell-Boltzmann distribution which can be considered as a generalization for
describing systems characterized by local correlations among their particles as
found in space and astrophysical plasmas. This paper presents all special cases
of kappa distributions as members of a general pathway family of densities
introduced by Mathai.
