Energy Loss of Particles in Pulsar Radio Emission Region

Extremely relativistic particles play an important role in various radiative mechanisms of pulsar radio as well as high-energy emission. It is thus very essential to estimate the Lorentz factor of these particles in the radiation regions both observationally and theoretically. In this paper, according to the frequency dependence of component separation and considering some radiation processes, we obtain the Lorentz factor and its variation in the radiation region observationally for seven multi-frequency observed pulsars. It is found that the Lorentz factor decays substantially in the emission region, and the decay can not be well understood by all known energy loss processes. This result hints that there are some unknown processes which are responsible to loosing energy effectively.