Filament motions in magnetized plasmas

Abstract

Interchange motions of magnetized plasmas due to either a non-uniform magnetic field or a gravitational field lead to charge polarization within a filamentary structure and set up convection. In this project we have provided a clear derivation of the two-field model equations that describe these filament motions. We have also derived an energy theorem for small amplitude oscillations.

We have derived the electron temperature equation for interchange motions and also described the coupling between electron temperature and electrostatic potential due to sheath currents leading to spin of filament structures. The calculations showed that the existing two-field model can be extended to the tree-field model. We have also showed that that the temperature field extends an energy theorem, but the mechanism of the interchange motions remains the same. This thesis may be considered as a first step to the three-field description of the filament motions in plasma.

Velocity scaling laws were also derived. It was shown, that the maximal center-of-mass velocity scales as a square root of the density amplitude only if this amplitude is small in comparison with the background density, for the amplitudes are large, the velocity scales as unity. It was also shown that in case of the constant background density the maximum center-of-mass velocity scales as a square root of the temperature amplitude independently on the background temperature. These scaling laws were verified numerically by the two-dimensional advection-diffusion solver.