Equipartition of the magnetic field and the electron energy in BL Lac jets

The traditional one-zone Synchrotron Self-Compton (SSC) model for the spectral energy distribution (SED) of BL Lacertae (BL Lac) objects, shows unexpected attribute that the energy density of nonthermal electrons Ue is much larger than the magnetic field UB. It is believed that the behavior of a plasma in a jet is a significant influence on equipartition. This paper considers an anisotropic SSC model for the electron momentum distribution. The model assumes that the angle between the direction of motion and the magnetic field can be very small or parallel when the highest energy electrons are accelerated. Therefore, the intensity of synchrotron radiation is significantly depressed. In this model, the magnetic field in the dissipation region is much stronger in the case of an isotropic distribution of nonthermal electrons. In this paper, we examine whether this model can predicts physically reasonable parameters, and we discuss some of its implications.