Low-frequency electron temperature and density oscillations in a cylindrical magnetoplasma are analysed numerically. Special attention is attached to the case of electron temperature and density gradients of opposite sign, which appear in RF-ring discharges. To guarantee best possible description of experimental findings, the analysis includes ambipolar electric fields, ion inertia and radial phase shifts of the perturbed plasma quantities, as a consequence of which spiral structures appear. The formalism is restricted neither to magnetized nor to cold ions.