Method of the Particle-in-cell simulation for the Y-Point in the pulsar magnetosphere

Abstract

Recent observations in the X-ray and Gamma-ray suggest that the emission region of the pulsar magnetosphere can be multifold. In particular, the open-close boundary of the magnetic field, so-called the Y-point, can be a new candidate place where magnetic field energy converts into plasma heat and/or flow energy. Here, we present a new Particle-in-Cell code, which can be applied to the Y-point of the pulsar magnetosphere in axisymmetric geometry. The electromagnetic solver is used in two-dimensional grid points with cylindrical coordinates (R, z), while the particle solver operates in three-dimensional Cartesian coordinates (x, y, z), where the Buneman-Boris method is used. The particle motion is treated in special relativity. The inner boundary conditions are set up to generate rotation of the magnetosphere by use of the force-free semi-analytic solution given by Uzdensky (2003, ApJ, 598,446). The code has been verified by dispersion relations of all wave modes in electron-positron plasmas. The initial test run is also presented to demonstrate the Y-shaped structure at the top of the dead zone on the light cylinder. We suggest that the structure is variable with quasi-periodicity with magnetic reconnection, and mat plasma will be accelerated and/or heated. In a time-averaged point of view, the break up of the ideal-MHD (magneto-hydrodynamics) condition takes place in the vicinity of the Y-point. © 2010. Astronomical Society of Japan.