Computer experiments on whistler and plasma wave emissions for Spacelab‐2 electron beam

Abstract

A funnel‐shaped VLF emission observed in the Spacelab‐2 electron beam experiment is studied by computer experiments using an electromagnetic particle code. The computer experiments demonstrated that broad‐band plasma wave emissions extending from a low frequency to the local plasma frequency are excited by a spatially confined thin electron beam. The emissions have parallel phase velocities satisfying the Landau resonance condition with the electron beam. Parts of the emissions below the electron cyclotron frequency can propagate away from the beam as oblique whistler mode waves. The computer experiments show a very clear funnel‐shaped emission, and show a remarkable similarity with that in the Spacelab‐2 electron beam experiment. The funnel‐shape of the whistler emissions is interpreted in terms of the perpendicular group velocity and, as a possible additional mechanism, the wave damping in the background plasma.