Asymmetric eigenmodes in a simple model plasmasphere

A theoretical plasma is supposed to be contained between two perfectly conducting cylinders. A magnetic field from a hypothetical line pole is postulated because the metric coefficients have similar properties to those of a dipole field. It is found, as expected, that the asymmetric hydromagnetic eigenmodes involve coupling of torsion and compression. Nevertheless the behaviour is found to be still roughly like that of a uniform field model. The modes are found to be either roughly torsional or roughly compressional, and the roughly torsional eigenfrequencies are found to be insensitive to the eigenmode structure across the field lines. It is therefore suggested that estimates of micropulsation spectra from the axisymmetric toroidal mode in the dipole field may be fairly valid whatever the true longitude distribution of the micropulsations.