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| Paper: |
Radioastronomy and the Study of Exoplanets |
| Volume: |
430, Pathways Towards Habitable Planets |
| Page: |
175 |
| Authors: |
Zarka, P. |
| Abstract: |
The relatively high contrast between planetary and solar low-frequency radio emissions suggests that the low-frequency radio range may be well adapted to the direct detection and study of exoplanets. Study of solar system planetary radio emissions (auroral as well as satellite induced) show that their primary engine is the interaction of a plasma flow with an obstacle in the presence of a strong magnetic field (of the flow or of the obstacle). A “radio–magnetic” scaling law has been derived that relates the emitted radio power to the magnetic energy flux convected onto the obstacle. An RS CVn magnetic binary for which both quantities are available is found to be consistent with this scaling law. Extrapolating it to the case of exoplanets and their plasma interaction with their parent star, it is found 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 hectodecameter range with intensity 103 to 106 times that of Jupiter (unless some unexpected “saturation” mechanism occurs). Corresponding flux densities should be detectable at the tens of parsecs range with modern radio arrays. Ongoing and future observational searches are briefly described, as well as the interests of direct radio detection, among which access to exoplanetary magnetic field measurements and comparative magnetospheric physics. |
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