The effect of photo-electric absorption on space-charge limited flow in pulsars

TL;DR

This paper investigates how photo-electric absorption affects ion acceleration in pulsar polar caps, showing that surface temperature limits electric fields and influences radio emission mechanisms.

Contribution

It provides new calculations of photo-electric cross-sections and ion transition rates considering high magnetic fields and surface temperatures, highlighting their impact on pulsar acceleration and emission.

Findings

Surface temperature above 10^5 K limits acceleration electric fields.

Ion beams are unstable and can generate coherent radio emission.

Photo-electric absorption significantly influences pulsar magnetosphere dynamics.

Abstract

Photo-electric absorption of blackbody photons is an important process which limits the acceleration of ions under the space-charge limited flow boundary condition at the polar caps of pulsars with positive corotational charge density. Photo-electric cross-sections in high magnetic fields have been found for the geometrical conditions of the problem, and ion transition rates calculated as functions of the surface temperatures on both the polar cap and the general neutron-star surface. The general surface temperature is the more important and, unless it is below 10^5 K, limits the acceleration electric field in the open magnetosphere to values far below those needed either for electron-positron pair creation or slot-gap X-ray sources. But such ion beams are unstable against growth of a quasi-longitudinal Langmuir mode at rates that can be observationally significant as a source of coherent radio emission.