A pulsar wind is a relativistic outflow dominated by Poynting energy at its base. Based on the standard ideal magnetohydrodynamic (MHD) model of pulsar wind neb- ulae (PWNe) with the ordered magnetic field, the observed slow expansion vPWN ≤ c requires the wind to be dominated by kinetic energy at the upstream of its termina- tion shock, which conflicts with the pulsar wind theory (s-problem). In this paper, we extend the standard model of PWNe by phenomenologically taking into account conversion of the ordered to turbulent magnetic field and dissipation of the turbu- lent magnetic field. Disordering of the magnetic structure is inferred from the recent three-dimensional relativistic ideal MHD simulations, while magnetic dissipation is a non-ideal MHD effect requiring a finite resistivity. We apply this model to the Crab Nebula and find that the conversion effect is important for the flow deceleration, while the dissipation effect is not. Even for Poynting-dominated pulsar wind, we obtain the Crab Nebula's vPWN by adopting a finite conversion time-scale of ∼ 0.3 yr. Mag- netic dissipation primarily affects the synchrotron radiation properties. Any values of the pulsar wind magnetization σw are allowed within the present model of the PWN dynamics alone, and even a small termination shock radius of ≤ 0.1 pc reproduces the observed dynamical features of the Crab Nebula. In order to establish a high-sw model of PWNe, it is important to extend the present model by taking into account the broadband spectrum and its spacial profiles.
|Publication status||Published - 2018 May 21|
- ISM: Individual objects (Crab Nebula)
- Magnetic fields
- Radiation mechanisms: Non-thermal
- Sars: Individual (Crab pulsar)
ASJC Scopus subject areas