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Centro de Astrofísica da Universidade do Porto

Solar and stellar magnetism

Pascal Petit

Magnetic fields are involved in many aspects of stellar physics. They are key parameters in physical processes like accretion, mass-loss, diffusion, convection, rotation and can therefore deeply influence stellar evolution. If many issues related to stellar magnetism remain open today, our understanding of the origin and impact of magnetic fields in solar-type stars have benefited from important progresses during the last decade, thanks to combined breakthroughs in observing techniques and numerical simulations. In this course, I review some of the most striking advances achieved in this domain for the Sun itself and, in a broader context, for solar analogues.

Sessão 1: Lecture I -- The magnetic Sun
24 março 2004

I will detail our present observational knowledge of solar activity, which has been monitored for almost four centuries and is now investigated down to spatial scales of order of 150~km on the solar surface. I will also discuss how secular fluctuations of solar activity may affect the Earth's climate.

Sessão 2: Lecture II -- Solar and stellar dynamos
14 abril 2004

The complex and variable magnetic field of the Sun is thought to originate from a series of MHD mechanisms called dynamo processes. I will review the current status of solar dynamo theories, which can now be directly confronted to helioseismological observations unveiling the internal velocity field of the Sun. I will also detail the translation of dynamo models to the stellar case, and the so-called solar-stellar connexion.

Sessão 3: Lecture III -- Impact of magnetic fields on stellar evolution
28 abril 2004

In this last part, I will review some of the most significant effects of magnetic fields on the physics and evolution of solar-type stars. I will especially emphasize the role of stellar magnetism in early phases of stellar evolution, with magnetospheric accretion and magnetically-driven stellar spin-down.