Cameron, R. H., Duvall , T. L, Jr., Schüssler, M., & Schunker, H.
Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany
The solar dynamo is a cycle where in one phase motions acting on poloidal magnetic flux generates toroidal flux, and in a subsequent phase motions act on the toroidal field to reverse the poloidal field. In Ref. 1, we determined the (azimuthally averaged) toroidal magnetic field at the solar surface using SOHO/MDI and WSO data using the method described in Ref. 2. We showed that the surface toroidal field corresponded to the presence of horizontal field in the photosphere during the emergence of active regions and ephemeral regions. The surface toroidal field can therefore be considered as a good proxy for the subsurface toroidal field of the global solar dynamo. Together with the observed surface poloidal field, which corresponds to the poloidal field relevant for the solar dynamo3, we then have observations of both the poloidal and toroidal fields relevant for the global solar dynamo for four solar cycles. Figure 1 shows the observed magnetic butterfly diagrams.
The basic features of the observations, over four cycles of both the poloidal and toroidal fields, can be reproduced by the updated Babcock-Leighton model1,4.
 R. H. Cameron, T. L. Duvall Jr., M. Schüssler, H. Schunker, 2018, A&A, 609, A56
 Duvall, Jr., T. L., Scherrer, P. H., Svalgaard, L., Wilcox, J. M. 1979, Sol. Phys., 61, 233
 R. H. Cameron, M. Schüssler, 2015, Science, 347, 1333
 R. H. Cameron, M. Schüssler, 2017, A&A, 559, A52