Theory of Magnetic-Field Turbulence in Disk Plasmas and Its Application to the Galaxy and Accretion Model of Compact X-Ray Binaries

Abstract

It has been recognized that the differential rotation and radial flow of plasmas in a disk geometry act to generate and amplify the magnetic-field fluctuations in it. The presence of such a magneto-hydrodynamic turbulence plays an essential part in the physical processes involved in various astrophysical objects, such as the Galaxy and the accretion model of compact X-ray sources (Prendergast and Burbidge 1968, Shakura and Sunyaev 1973, Eardley and Lightman 1975, and many others). In the former case the theory should be relevant directly to the question on the origin of the Galactic magnetic field; the spectral distribution of magnetic-field fluctuations may then be correlated with the observational data such as the energy dependence of the anisotropy and the total path length of the cosmic rays. In the latter case the flux of angular momentum carried away by the stress tensor of the magnetic field enables the matter to flow toward the accreting star ; the static and dynamic properties of such an accretion disk are vitally controlled by the rate of such an angular-momentum transfer in the plasma. In the cakes of accretion onto a magnetic neutron star, the disk’s inner boundary is determined by the pressure balance between the stellar magnetic field and the accreting plasma (the Alfvén. surface). The eventual fall of the plasma onto the stellar surface must he accounted for in terms of the theory of plasma diffusion across the Alfvén surface; the basic processes involved are the anomalous electric resistivity in the boundary domain caused by the presence of magnetic-field fluctuations in the disk (Ichimaru, to be published).