EXTRAGALACTIC JET COLLIMATION DUE TO CHERENKOV DAMPING OF DISCRETE ALFVEN WAVES

We have shown that discrete Alfven waves can drive noninductive electr ic current at the level necessary to explain the observation, via radi otelescope, of extragalactic jet (EJ) collimation. The EJ is modeled a s a cylindrical current carrying plasma column surrounded by vacuum [e xternal EJ medium], with L much greater than a where L and a are the E J length and radius, respectively. Discrete Alfven waves (DAW) are glo bal Alfven modes which propagate disturbing all the plasma column. The y can be described by the inclusion of finite ion cyclotron frequency and/or the equilibrium plasma current.