AN EMISSION MECHANISM FOR EXTRAGALACTIC RADIO JETS

The observed emissions of radio waves from extragalactic radio jets ar e customarily interpreted in terms of the incoherent synchrotron radia tion produced by a nonthermal population of relativistic electrons (or positrons) gyrating in a magnetic field. Such an interpretation requi res, by necessity, a mechanism (or mechanisms) to constantly reenergiz e the particles in directions transverse to the magnetic field in mome ntum space. This paper, on the other hand, presents a possible alterna tive mechanism for radiation emission that does not require transverse reacceleration, albeit the theory is only preliminary at this stage. The emission mechanism described in the present paper is an induced pl asma process that results from a nonlinear coupling of the electrostat ic beam mode with the transverse electromagnetic mode. The beam mode i s excited when a stream of ultrarelativistic electron-positron pair pl asma nonlinearly interacts with low-frequency intrinsic turbulence. Th e only source of free energy for the instability is the streaming moti on of the pair plasma. Therefore, as opposed to the incoherent synchro tron model, this mechanism (if, indeed, it is operative) has an advant age of not having to rely on the concept of constant renenergization o f particles in the transverse direction.