Comparison of the Past Two Solar Minima from the Perspective of the Interior Dynamics and Dynamo of the Sun

Solar cycle 23 behaved differently than cycle 22 in many ways. Certain properties, namely the long minimum at the end of cycle 23, weakening of polar fields, shrinking of polar coronal holes, reduction in the terrestrial atmospheric neutral density layer, have been identified as unusual compared to several past cycles. The origin of these differences most likely lies in the ways the dynamo has operated that led to distinctly different generation and evolution of the large-scale magnetic fields in cycles 22 and 23. Certain differences in the properties of Galactic-Cosmic Rays during cycles 22 and 23 have recently been explained by the differences in evolutionary pattern of coronal holes, which are linked to the dynamo-generated large-scale magnetic fields. In this paper, I will discuss the differences in the solar interior dynamics, particularly the properties of flow fields and their influence in governing the evolution of dynamo-generated magnetic fields during cycles 22 and 23, respectively.     

Flux-Transport Solar Dynamos

Large-scale solar dynamo models were first built by Parker (1955). Over the past half a century these models have evolved significantly. We discuss here the development of a class of large-scale dynamo models which include, along with the α-effect and Ω-effect, an important third process, flux transport by meridional circulation. We present the properties of this ‘flux-transport’ dynamo, including the crucial role meridional circulation plays in giving this dynamo predictive power.