Magnetically-driven planetary radio emissions and application to extrasolar planets

At least six intense nonthermal planetary radio emissions are known in our solar system: the auroral radio emissions from the Earth, Jupiter, Saturn, Uranus and Neptune, and the radio bursts from the Io-Jupiter flux tube. The former are thought to be driven by the solar wind flow pressure or energy flux on the magnetospheric cross-section, while the latter is a consequence of the Io-Jupiter electrodynamic interaction. Although in the solar wind, the flow ram pressure largely dominates the magnetic one, we suggest that t he incident magnetic energy flux is the driving factor for all these six ra dio emissions, and that it can be estimated in the same way in all cases. C onsequences for the possible radio emission from extrasolar planets are exa mined. 'Hot Jupiters', if they are magnetized, might possess a radio emissi on several orders of magnitude stronger than the Jovian one, detectable wit h large ground-based low-frequency arrays. On the other hand, 'giants' anal ogous to the Io-Jupiter interaction in the form of a pair star/hot-Jupiter are unlikely to produce intense radio emissions, unless the star is very st rongly magnetized.