A QUANTITATIVE MODEL OF COHERENT, STIMULATED-EMISSION IN ASTROPHYSICAL JETS

On the basis of issues raised by observations of BL Lac objects and th e qualitative jet model proposed by Baker et al. in 1988, we have been led to consider the quantitative role of coherent, stimulated emissio n in jets and construct a new jet model of blazars in which a relativi stic electron beam with an axial symmetric, power-law distribution is injected from the central engine into the jet plasma. We study quantit atively the synchrotron emission of the relativistic electron beams. U sing the weak turbulent theory of plasma, we discuss the interaction b etween relativistic electron beams and jet plasma, and the roles of st imulated emission. The main results are: (1) The synchrotron emission increases sensitively with the increase of the angle between the direc tion of the beam and the magnetic field. When the direction of the bea m is vertical to the magnetic field, the synchrotron emission reaches its maximum, i.e. the emitted waves are beamed in the direction of the jet axis. We suggest that radio selected BL Lac objects belong to thi s extreme classification. (2) The synchrotron emission of the relativi stic beam increases rapidly with the increase of the Lorentz factor of the relativistic electron, gamma, when gamma less-than-or-equal-to 22 .5, then decreases rapidly with increase of (3) The stimulated emissio n also increases with increasing Lorentz factor gamma of the relativis tic electrons when gamma less-than-or-equal-to 35 and then decreases w ith the increasing gamma. The maximum stimulated emission and the maxi mum synchrotron emission occur at different frequencies. Stimulated em ission is probably very important and reasonable flare mechanism in bl azars. (4) The rapid polarization position angle (PA) swings may arise from the interaction between the relativistic electron beam and the t urbulent plasma.