THREE-DIMENSIONAL RELATIVISTIC MAGNETOHYDRODYNAMIC SIMULATIONS OF CURRENT-DRIVEN INSTABILITY. II. RELAXATION OF PULSAR WIND NEBULA

Abstract

We have investigated the relaxation of a hydrostatic hot plasma column\ncontaining toroidal magnetic field by the Current-Driven (CD) kink instability\nas a model of pulsar wind nebulae. In our simulations the CD kink instability\nis excited by a small initial velocity perturbation and develops turbulent\nstructure inside the hot plasma column. We demonstrate that, as envisioned by\nBegelman, the hoop stress declines and the initial gas pressure excess near the\naxis decreases. The magnetization parameter \\sigma, the ratio of the Poynting\nto the kinetic energy flux, declines from an initial value of 0.3 to about 0.01\nwhen the CD kink instability saturates. Our simulations demonstrate that\naxisymmetric models strongly overestimate the elongation of the pulsar wind\nnebulae. Therefore, the previous requirement for an extremely low pulsar wind\nmagnetization can be abandoned. The observed structure of the pulsar wind\nnebulae do not contradict the natural assumption that the magnetic energy flux\nstill remains a good fraction of the total energy flux after dissipation of\nalternating fields.\n