ÃÛÌÒTV

Pulsar wind nebulae (PWN) - with the Crab nebula as prime example - provide a unique test-bed for the study of highly relativistic processes right at our astronomical doorstep. In this presentation I will show results from 3D relativistic MHD simulations of PWN. Of key interest to our study is the long standing "sigma-problem" that challenges MHD models of pulsars and their nebulae now for 3 decades. Earlier 2D MHD models are limited to a purely toroidal field geometry which leads to an exaggerated compression of the termination shock and polar jet - in contrast to the observations. In three dimensions, the toroidal field structure is susceptible to current driven instabilities and a turbulent cascade develops in the nebula. Kink instability and turbulent magnetic dissipation govern the dynamics of the nebula flow. I will demonstrate how these additional processes lead to a resolution of the sigma-problem.

In addition, I will present polarized synchrotron maps and animations constructed from the 3D simulations, showing a remarkable resemblance with the available observations of Crab nebula.