ABSTRACT
The single-fluid MHD models represent a radical generalisation of the one-component block models. However, as shown in the introduction, even the fundamental characteristic of the plasma – Langmuir frequency – can be derived only from the two-component block model. A suitable demonstration of the special features of plasma processes is the analysis of the fall of a plasma bar in the magnetic field, carried out within the framework of the two-component block model in chapter 1 (section 1.3.2). It was shown that the quasi-autonomous nature of the dynamics of every component results in the formation of a strong electrical field in the plasma volume. This field is highly sensitive to the external conditions, and an example of this is the situation with the toroidal drift discussed in section 1.7. The examples show that it is often necessary to transfer to the two-fluid plasma model. This model can be regarded as a result of dividing each of the two blocks into N→∞ quasi-autonomous ‘droplets’. The present chapter is concerned with the formulation of the two-fluid model on the basis of convincing ‘physical’ considerations and with also application of the model for calculating a number of plasma-dynamic structures. A strict scheme of the derivation of the equations for this model on the basis of the collisional kinetics will be described in chapter 5.
