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tokens: of the outer star forming rings in visually unbarred galaxies are shown in Fig. 1 . This figure presents a particular class of ring galaxies, those with accreted star forming rings in axisymmetric S0s which are especially suitable to host a dynamo process. The class is however far from being homogeneous. Figure 1 illustrates that the ring galaxies of interest can vary considerably in appearance. This is why we have to consider a variety of possible dynamo effects that might contribute to magnetic field formation in such scenarios and experiment with the dynamo numbers that estimate the strengths of the effects. A particular challenge is that NGC 4513, shown in the first panel of Fig. 1 , has a counter-rotating ring. IC 5285, UGC 5936, and UGC 9980 do not demonstrate observable radial gas velocities, thus ruling out a collisional origin for their rings ( Ilyina Sil’chenko 2011 ; Ilyina et al. 2014 ; Katkov et al. 2015 ). In fact, to discriminate between the origin scenarios for an outer ring in a particular galaxy, kinematical data are necessary, and 3D (two spatial coordinates on the plane of sky and one along the wavelength axis Courtes 1995 ); spectral data are especially useful ( Moiseev Bizyaev 2009 ). The collisional rings and OLR (Outer Lindblad Resonance) rings generate radial gas outflow while accreted gaseous rings rotate circularly, although sometimes outside the main galactic plane. In addition, the optical spectral data provide the possibility of determining the excitation mechanism for the ionized (warm) gas. The flux ratios of strong emission lines discriminate easily between the mechanisms of shock excitation and of ionization by UV radiation of young stars ( Baldwin et al. 1981 ; Veilleux Osterbrock 1987 ). To facilitate the action of a dynamo in magnetic-field generation, we need long-lived (order of Gyrs) rings; hence collisional rings, with their lifetimes of a few hundred Myr, are unlikely to be candidates; a supply of free electrons, hence an ionized state of the gas that can be provided and supported by continuous star formation in the rings; regular circular gas rotation in the main galactic planes, presumably with a flat rotation curve, to provide a differential character for the gas rotation. In some ways rings, generated by accretion may be be the most favourable for our investigation, with estimated lifetimes possibly approaching the Hubble time ( Buta Combes 1996 ). Based on the results of Ilyina Sil’chenko (2011) , Ilyina et al. (2014) and Katkov et al. (2015) we select a small sample with the properties mentioned above and present it in Fig. 1 . The typical properties of these galaxies will be used in the further theoretical consideration of the dynamo magnetic-field generation in ring galaxies. Some extension of the typical picture can be also considered, by taking into account possible cases of the outer gas counter-rotation, as in NGC 4513 ( Ilyina et al. 2014 ), or strong flaring of the gas layer in the