Interaction of pulsar winds with interstellar medium: numerical simulation

A time-dependent numerical simulation of relativistic wind interaction with interstellar medium was performed. The winds are ejected from the magnetosphere of rotation-powered pulsars. The particle flux in the winds is isotropic while the energy flux is strongly anisotropic. Pure hydrodynamical winds and magnetized winds with magnetization in the range 3 x 10(-3)-10(-1) were modelled. The numerical solutions reproduce the most spectacular features observed in the central part of the plerions: toroidal structure and jet-like features. A comparison of the solutions with the observations confirms that magnetization of the wind from a pulsar in the Crab nebula is of the order of 3 x 10(-3). The plasma flow in the nebula is variable. The variability has different time-scales. Non-periodic 2-3 yr scale variations are superimposed on the quasi-periodical variations with period similar to 40 yr. An increase of the wind's magnetization results in a decrease of the size of the synchrotron nebula. The size of the Vela nebula can be reproduced provided that the wind from Vela is more highly magnetized then the wind from Crab. Nevertheless, the magnetization of the wind from the Vela pulsar is most likely below 0.1..