Dynamo of the Sun and Solar-Type Stars

Laboratoire d'Astrophysique, Observatoire de Grenoble, CNRS/Université Joseph Fourier, BP. 53, 38041 Grenoble Cedex, France

Abstract

The objective of this paper is to give a review of solar and stellar activity, from the observationnal constraints to dynamo models. I first review solar observations and insist on the various scales. Then I describe the photospheric magnetic structures (from spots and plages to the magnetic network and internetwork magnetic fields) and the energetic events in the chromosphere and corona, such as prominences, flares and coronal mass ejections. It is mostly photospheric observations (in addition to the results obtained with helioseismolohy concerning the internal rotation) which are providing the important constraints for dynamo models, that are reviewed. However the energetic events can also be used as tracers of solar activity and have a significant impact on earth. Stellar activity is then reviewed, including results on differential rotation. I insist on the comparison with solar properties. I then come back on the constraints these stellar observations bring to dynamo models.