Seismology and the Dynamo: History and Prospects

The rapid "advances" in our knowledge and understanding of solar and stellar dynamos that resulted from the development of mean-field dynamo theory were sent into even more rapid retreat in the 1980s by difficulties in explaining observed features of the solar cycle, and especially by the new helioseismically derived differential rotation profiles. The climb back out of the mire has been slow and uncertain. A promising-but by no means universally accepted-route is afforded by the resurrection of Babcock-Leighton (flux transport) models of the dynamo, where meridional circulation plays a dominant 'conveyor belt' role, aided and abetted by other near-surface flow patterns which disperse old flux poleward. In this brief overview, we review what helioseismology has told us about meridional and near-surface flows, and muse on the prospects for improved flow measurements in the future.