A burst emission mechanism for coherent radiation from pulsars

Abstract

Various mechanisms for generating coherent curvature radiation have been proposed¹ to explain the high brightness temperature of pulsars at radio frequencies. The bunching of counterstreaming charged particles^2–5, although requiring rather special conditions and subject to criticism⁶, has hitherto seemed the most plausible. Here we propose an entirely new mechanism of ‘burst emission’, which initiates at the surface of a neutron star and occurs naturally without any need to postulate special conditions. We argue that the induced electric field in the near magnetosphere of a rotating neutron star is sufficiently strong to detach moderately large grains of solid matter from the surface in the polar-cap regions. The detached grains erupt and form ascending plumes or jets of dense and highly charged gas. These thread-like plumes, of length h ≳ 10² cm, then accelerate along the open magnetic field lines and emit intense partially coherent radiation, at radio frequencies, with a low-frequency cutoff at c/h. Our estimates indicate that burst emission can account for the principal characteristics of the observed radiation from pulsars at radio frequencies.