We calculate the effect of a strong dipole magnetic field on non-axisymmetric oscillations for roAp stars, with a typical range of photospheric magnetic fields Bp [0.5-1.5] kG. As Dziembowski & Goode (1996), we find that the oscillations are strongly affected by such magnetic fields in two different ways. The first one concerns the stability of modes, which are damped due to dissipation by Alfv...

We present a perturbation theory for studying the instabilities of non-axisymmetric gaseous discs. We perturb the dynamical equations of self-gravitating fluids in the vicinity of a non-axisymmetric equilibrium, and expand the perturbed physical quantities in terms of a complete basis set and a small non-axisymmetry parameter ǫ. We then derive a linear eigenvalue problem in matrix form, and det...

In a recent important paper, Papaloizou & Pringle (1984) have investigated the dynamical stability of a thick, differentially rotating disc of uniform entropy and uniform specific angular momentum. They find a strong global non-axisymmetric instability which grows on a dynamical time-scale. Here we show that a similar instability exists even in thin discs of arbitrary specific angular momentum....

The dynamical effects of magnetic fields in models of radiative, Herbig-Haro (HH) jets have been studied in a number of papers. For example, magnetized, radiative jets from variable sources have been studied with axisymmetric and 3D numerical simulations. In this paper, we present an analytic model describing the effect of a toroidal magnetic field on the internal working surfaces that result f...