Magnetic fields on Extrasolar Planets: From Radio Emission to High-Energy Cosmic Rays

Event though there is no firm evidence for their presence to date, a considerable fraction of extrasolar planets are expected to host a magnetic field. At the same time, the planetary magnetic field plays an important role in the evolution of a planet, determining the protection of its atmosphere against the stellar wind, against stellar coronal mass ejections (CMEs) and against cosmic rays. In view of the importance of exoplanetary magnetic fields, various attempts have been undertaken in order to predict their intensity. We will present different models for planetary magnetic fields and compare their results. We will also present a number of methods that have been suggested for the observations of exoplanetary magnetic fields, the most promising of which is the detection of planetary radio emission. We will also discuss the implications of the magnetic field on the planetary atmosphere via the effect of high-energy cosmic rays.