Doppler Imaging of Stellar Magnetic Fields

Magnetic fields play very important role in the formation and evolution of stars. Magnetism is often invoked as an explanation of various phenomena, ranging from different types of stellar variability to the magnificent shapes of expanding envelopes of dying stars. Magnetic fields are also suggested to be responsible for creating and supporting other structures on stellar surfaces, such as chemical inhomogenities and temperature spots. This picture is based on direct analogy to dark spots associated with regions of strong magnetic fields on the solar surface. However, we cannot directly see the surfaces of distant stars and, until recently, stellar magnetic structures and their roles remained largely hypothetical. We suggest to change this unsatisfactory situation and derive accurate stellar magnetic maps using newly developed magnetic Doppler Imaging method. In this technique images of stellar surfaces are reconstructed using observations of changes in intensity and polarisation state of stellar radiation due to rotational modulation of the aspect at which stellar surface spots are observed from Earth. Together, new observations and new modelling approach would allow us to study stellar magnetic `geography` in such fine details which were possible before only for the sun. As a result of the project, we foresee a major improvement of our knowledge about magnetic fields on the surfaces of several types of stars. We will learn how the fields are organized, how they form, evolve and interact with the stellar matter. This work will constitute an important contribution to stellar astrophysics.