THREE DIMENSIONAL STUDY ON PULSAR MAGNETOSPHERE WHICH CREATES ELECTRON-POSITRON PAIRS

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Mechanism of particle acceleration in the pulsar magnetosphere is mostly studied in the axisymmetric case because analysis in non-axisymmetric case, i.e., in the case that the magnetic axis is inclined to the rotation axis, is tremendously difficult. This project callenges to this non-aligned case. Note the real pulsar system is indeed non-aligned completely three dimensional system. Although we have to deal with large numerical calculation, we overcome this problem by using a special porpouse computer. The use of a special porpouse computer makes this project distinctive to other works.(1) In the first step, we analytically study the formation of the field-aligned electric field, which accelerate particles on the polar caps. There are two kind of magnetic field lines : the field lines curving toward the rotation axis and those curving away the rotation axis. It was proposed that acceleration takes place only on the 'toward field lines'. However, I showed that particle acceleration takes place regardless of field line curvature if the current density is larger than a critical value. This acceleration is shown to be strong enough to cause electron-positron pair creation cascade. (Shibata 1997)(2) In the non-aligned case, there is an effect of the displacement current on the field structure. The convection current also contribute to the field structure. Including the both effects, we calculate the field structure of the perpendicular rotator in the force-free case. (Mestel and Shibata, 1998 in preparation)(3) I developed a particle-code for the three-dimensional magnetospheric model on the special porpouse computer Harp-3 (2.2Gflops). Hape-3 was original made for gravitationary interacting particles, but we use it for Coulomb interaction. This code will be used to study a electrosphere in which pair creation takes place. This is an important step for the future calculation for particle simulation of the magnetosphere with pair discharge.