On the Electric Field Screening by Electron-Positron Pairs in the Pulsar Magnetosphere II

Abstract

We study on the self-consistency of the pulsar polar cap model, i.e., the problem of whether the field-aligned electric field is screened by electron-positron pairs that are injected beyond the pair production front. We solve the one-dimensional Poisson equation along a magnetic field line, both analytically and numerically, for a given current density incorporating effects of returning positrons, and we obtain the conditions for the electric-field screening. The formula which we obtained gives the screening distance and the return flux for given primary current density, field geometry and pair creation rate at the pair production front. If the geometrical screening is not possible, for instance, on field lines with a super-Goldreich-Julian current, then the electric field at the pair production front is constrained to be fairly small in comparison with values expected typically by the conventional polar cap models. This is because (1) positive space charge by pair polarization is limited to a small value, and (2) returning of positrons leave pair electrons behind. A previous belief that pair creation with a pair density higher than the Goldreich-Julian density immediately screens out the electric field is unjustified at least for for a super Goldreich-Julian current density. We suggest some possibilities to resolve this difficulty.

8 pages, 5 figures, accepted for publication in MNRAS

References in corpus (1)

• Electrodynamic Structure of an Outer Gap Accelerator: Location of the Gap and the Gamma-ray Emission from the Crab Pulsar

Cited by in corpus (10)

• Large-Amplitude, Pair-Creating Oscillations in Pulsar and Black Hole Magnetospheres
• Theory of pulsar magnetosphere and wind
• A two-dimensional electrodynamical outer gap model for gamma-ray pulsars: Gamma-ray spectrum
• An Idealized Pulsar Magnetosphere: the Relativistic Force-Free Approximation
• Electrodynamics of Outer-Gap Accelerator: Formation of Soft Power-law Spectrum Between 100 MeV and 3 GeV
• Electrodynamics of Magnetars IV: Self-Consistent Model of the Inner Accelerator, with Implications for Pulsed Radio Emission
• Axisymmetric force-free magnetosphere of a pulsar. I. The structure close to the magnetic axis
• Electric field screening by a proton counterflow in the pulsar polar cap
• Electrostatic Instability in Electron-Positron Pairs Injected in an External Electric Field
• Coherent Curvature Radiation and Proton Counterflow in the Pulsar Magnetosphere