Showing papers by "Roger Blandford published in 1983"
206 citations
TL;DR: The resonant character of magnetic field damping by moving magnetic monopoles allows the field to survive indefinitely when the monopole plasma frequency is sufficiently large, even if the field is immersed in a conducting plasma.
Abstract: The resonant character of magnetic field damping by moving magnetic monopoles allows the field to survive indefinitely when the monopole plasma frequency is sufficiently large, even if the field is immersed in a conducting plasma. Dynamo growth of galactic field can still occur on time scales \ensuremath{\sim}${10}^{7}$-${10}^{8}$ yr in the presence of a halo composed of monopoles. A linear stability analysis suggests that a monopole's mass is $m\ensuremath{\sim}{10}^{18}$ GeV/${\mathit{c}}^{2}$ and that the monopoles should have an anisotropic flux \ensuremath{\sim}1 ${\mathrm{m}}^{\ensuremath{-}2}$ ${\mathrm{yr}}^{\ensuremath{-}1}$ ${\mathrm{sr}}^{\ensuremath{-}1}$.
22 citations
TL;DR: In this article, it was shown that a sufficient overpressure with respect to the ambient interstellar medium can be achieved if the radius of the jet is reduced by a factor 10-100, and the converging flow becomes dissipative.
Abstract: There has been much theoretical discussion of the confinement of the radio jets associated with extragalactic radio sources. There are now several examples of sources where the minimum pressure inferred in the jets appears to exceed the external gas pressure, which suggests that magnetic pinching may be playing an important part in the confinement. This issue has been highlighted by recent remarkable observations, using the Very Large Array, of the radio lobes associated with the galactic X-ray source Sco X-1 by Fomalont et al. We argue here that these results necessitate magnetic focusing and that this also strengthens the case for magnetic focusing in the extragalactic sources. We show that a sufficient overpressure with respect to the ambient interstellar medium can be achieved if the radius of the jet is reduced by a factor 10–100, and the converging flow becomes dissipative. The radio lobes which form at that point quickly die out again due to electron expansion losses in the now rapidly diverging jet. On the basis of this model it is predicted that the Faraday rotation changes sign across the radio lobes, and that the shape of the lobes should be conical with the apex pointing towards Sco X-1.
20 citations
TL;DR: In this article, it is proposed that the jet which has been observed protruding from the northern rim of the Crab Nebula is a tubular trail of material lost by the presupernova star during its red giant phase.
Abstract: It is proposed that the jet which has been observed protruding from the northern rim of the Crab Nebula is a tubular trail of material lost by the presupernova star during its red giant phase. The movement of the red giant's stellar wind is analyzed to show that the mass profile downstream should be concentrated within a narrow cylinder. The parameters of the tube predicted by this model are presented and an observational test of the model based on the hydrogen-to-helium abundance ratio in the jet and in the Nebula as a whole is suggested; the model predicts that the ratio in the jet should be larger.
16 citations