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Planet–star plasma interactions

Published online by Cambridge University Press:  06 January 2010

T. Montmerle ,
D. Ehrenreich ,
A.-M. Lagrange  and
P. Zarka
P. Zarka*
Affiliation:
LESIA, Observatoire de Paris–CNRS–UPMC–Univ. Paris Diderot, 92190 Meudon, France
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Abstract

Planet–star plasma interactions can be described as the interaction of a plasma flow with an obstacle, each being possibly magnetized. Examples of the 4 possible situations are found in our solar system, with intense radio emissions produced in 3 cases out of 4, when either the flow or the obstacle is strongly magnetized. Scaling laws are derived that relate the emitted radio power to the power dissipated in the various corresponding flow–obstacle interactions. They are generalized as a “radio–magnetic” scaling law between the output radio power and the magnetic energy flux convected onto the obstacle. Extrapolating it to the case of exoplanets, we find that hot Jupiters may produce very intense radio emissions due to planetary magnetospheric interaction with a strong stellar wind, reconnection between planetary and stellar magnetic fields, or unipolar interaction between the planet and a magnetic star (or strongly magnetized regions of the stellar surface). Emitted radio power is expected in the hecto–decameter range with intensity 103 to 106 times that of Jupiter (unless some “saturation” mechanism occurs). Corresponding flux densities should be detectable at tens of parsecs range with modern radio arrays. We briefly discuss ongoing observational searches as well as the interests of direct radio detection.

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 41: Physics and Astrophysics of Planetary Systems , 2010 , pp. 441 - 454
Copyright
© EAS, EDP Sciences, 2010

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