[en] A survey is made on the problems of the edge plasmas, to which the analyses based on the MHD theory have been successfully applied. Also discussed are the efforts to extend the model equation to more general (and important as well) problems such as H-mode physics. An overview is first made on the advantages of the MHD picture, and the necessary supplementary physics are examined. Next, one- and two-dimensional models of the spatial structure of the edge plasma is discussed. The results on the stationary structure, both analytical and numerical, are reviewed: Typical example as well as the scaling law are shown. The instabilities associated with edge plasma is next reviewed. The surface kink mode, ballooning mode, interchange mode, resistive interchange mode and thermal instability are discussed. Role of the geometry such as the location of the X-point is studied. Influences of the atomic processes, and those of the radial electric field are also discussed. The analysis of the H-mode transition physics is finally discussed. The boundary plasma is a nonlinear media which possesses the possibility for bifurcation in which the radial electric field plays a key role. The model of the ion viscosity is also studied. Transition physics is developed. Analysis on the self-generating oscillation is shown and the relation with ELMs is discussed. After reviewing these problems, several comments are made to what directions the study can be deepened. (author) 53 refs

[en] Presentations given in the IAEA technical committee meeting on impurity control (held in JAERI from 13 to 15 February, 1989) are summarized, putting the emphasis on the physics modelling of the plasma related to the impurity production and confinement. (author)

[en] A prospect of plasma physics at the turn of next century is discussed. The theme of this conference identifies the future direction of the research related with plasmas. Main issue is the potential and structure formation in plasmas; More specifically, structures which are realized through the interaction of electromagnetic fields, in particular that with electric fields, in non-equilibrium state. An emphasis is made to clarify the fundamental physics aspects of the plasma physics in fusion research as well as that in the basic research of plasmas. The plasma physics will give an important contribution to the solution of the historical enigma, i.e., all things flow. Having an impact on human recognition of nature and showing a beauty in a law, the plasma physics/science will demonstrate to be a leading science in the 21st century. (author)

[en] New model of the L/H transition in tokamak plasmas is presented. Nonambipolar particle losses determine the consistent radial electric field near the plasma periphery. ''Cusp type catastrophe'' in the space of the radial electric field, particle flux and edge gradients is found. At the transition condition, plasma loss can take multiple values for one profiles of density/temperature near the edge. Critical edge condition is obtained. (author)

[en] A new refined model of the L-mode and H-mode transition in tokamaks is presented based on the bifurcation of the radial electric field, E_r, near edge. The radial gradient of E_r is newly introduced to explain the sudden change of fluctuations as well as plasma fluxes at the onset of transition. This model predicts that the L-to H-mode transition is associated with the decrease of dE_r/dr causing reduction of particle and energy fluxes at critical gradient. (author)

[en] Finite amplitude solution of helical equilibria of current-carrying plasmas bounded by a perfectly conducting cylinder is obtained. The nonlinear saturation levels of the fixed boundary MHD modes are also obtained near the marginal stable points. It is shown that by shaping the current density profile the saturation levels can be suppressed. (auth.)

[en] By means of the neighbouring equilibrium method the saturation level of the kink instability of a current carrying plasma column is investigated. We obtain the helical equilibrium which is the stationary saturated stage of kink instability. The analysis is performed for the rounded current profile case and shows that the shell has very strong suppression effect on the saturation level. (auth.)

[en] Helical equilibria and criteria for the kink instability have been obtained numerically for various current distribution, including camel hump distribution. It is found that the unstable region expressed by q(a) is the largest in the case of uniform current. (auth.)

[en] An anomalous parallel current driven by radial flux in tokamak is discussed. Drift waves, which cause an anomalous cross field diffusion, can generate a parallel current in a sheared magnetic field, if the fluctuation level has radial dependence. (author)

[en] A new method to analyze the MHD kink instability in the cylindrical approximation is presented. Using the nonlinear equilibrium equation with the helical perturbation method, an expression for the growth rate of instability of a perturbation is obtained. For m=1 mode, the growth rate and the stability-instability criterion, q(a)=1, are calculated analytically for an arbitrary current distribution. The growth rate is also calculated in the case of a uniform current. (auth.)