A particle simulation for the global pulsar magnetosphere – II. The case of dipole field

Authors


E-mail: tomohide.wada@nao.ac.jp (TW); shibata@sci.kj.yamagata-u.ac.jp (SS)

ABSTRACT

The main issue regarding the pulsar magnetosphere is how the rotation power is converted into both particle beams which cause pulsed emissions, and a highly relativistic wind of electron–positron plasmas which forms surrounding nebulae shining in X-rays and TeV γ-rays. As a sequel to our previous paper, we carried out a three-dimensional particle simulation for the axisymmetric global magnetosphere. We present the results of additional calculations, which are higher resolution models and higher pair creation rate cases, and a detailed analysis for the solution. We confined our work to demonstrating the cases of low pair creation rates, i.e. where the magnetic field is a fixed dipole. The radiation drag of the plasma was taken to be in a form with the curvature radius along the dipole magnetic field. The electrostatic interactions were calculated using a programmable special-purpose computer, GRAPE-DR. We found that once pair creation begins in the outer gaps, both positively and negatively charged particles begin to drift across the closed magnetic field due to radiation drag, and they create an outflow. Eventually, the steady magnetosphere has outer gaps, both positively and negatively charged outflow of plasma and a region in which the electric field is dominant extending from the equator. In the steady state, the magnetic field generated by the magnetospheric current is comparable to the dipole magnetic field outside several light radii from the star. In a much higher pair creation rate model, the effect of the modification of the magnetic field will bring about modification of the outflow of the plasma, requiring further study with a higher pair creation rate model in a subsequent paper.

Ancillary