Physics of the Sun
The Sun is an active and variable star. Well known signatures of the 11-year activity cycle are sunspots, flares, and coronal mass ejections. During solar flares an enormous amount of energy is released within a short time of some seconds to hours. The activity phenomena are determined by the solar magnetic field. Our work in the research group »Physics of the Sun« is focused on the observation and analysis of the magnetic activity in the solar atmosphere. That is done by optical and by radio astronomical methods. Due to its proximity the Sun can be well observed with high spatial and temporal resolution. Learning from the Sun to understand other stars – this is one aim of the research topic »Solar-Stellar Connection«. Our technical civilization is sensitive to the solar activity. This became apparent, e.g., during the sequence of strong flares in October/November 2003. The impact of solar activity on the terrestrial surroundings is summarized in the term »Space Weather«. The improved understanding of the solar activity is important for Astrophysics and for the human civilization.