| The structure of rotational discontinuities of the magnetic field in a plasma is a subject of basic interest and importance. In this thesis multi-fluid model is developed to describe this phenomenon in a collision-free plasma. The conservation laws obtained in this work provide useful information about the electrostatic structure (the electric phase relation) of the discontinuity layer, and about the rotation rate and total rotation angle of the tangential magnetic field component, as well as the sense of polarization. The jump conditions given by the multi-fluid model contain the results obtained by Hudson and by Landau as special cases. To apply the general theory, various physical models are worked out. Electrostatic soliton solutions, which occur in layers of width comparable to the Debye length (lamda)(,D), provide a small magnetic field rotation angle, of the order (lamda)(,D)/(lamda)(,i). Shock-pair solutions give layers with thickness comparable to or greater than the ion inertial length and produce a substantial change of the angle of rotation of the magnetic field. Soliton trains, consisting of many single solitons, are also shown to be possible. Large deviations from charge neutrality occur in these models. The various physical quantities needed in the calculation, such as the density and the stress tensor, etc., are obtained approximately by using either an equation of state or a distribution function. The application of the rotational discontinuity structures found to the magnetopause, in the solar wind, and above the auroral zones are also mentioned briefly. |
