ABSTRACT
In §2.2 and §2.3 we referred to the generation of large-scale magnetic-field structures by fluid motion and the high collimation of bipolar jets from an accretion disk. A useful tool for investigating these phenomena is the magnetohydrodynamic (MHD) approximation, specifically, the one-fluid approximation [2.24, 6.1]. In what follows, we shall give its brief account and refer to the limitation.
