Instability. • Resonance of a circularely polarized wave with the gyration of the electrons at the cyclotron frequency. The polarization depends on the magnetic hemisphere • Emission frequency close to the cyclotron frequency, proportionnal to the magnetic field. The observed frequency tells the strength of the exoplanet magnetic field ! The emissions are modulated by the magnetic field Modulation with the exoplanet's rotation period ! What do these emissions looks like ?
the Jupiter's emissions. • The main radio emissions of Jupiter are due to its interaction with Io. • Short interaction => sources localized in longitude • Radio emissions appear as arcs in the time-frequency plane
• Can be modeled, with physical assumption on the beaming angle. • Online tool : ExPRES (Exoplanetary and Planetary Radio Emission Simulator). • We can model observation of exoplanetary radio emissions to derive physical parameters of the emitting exoplanet.
solar wind flow long duration (hours) and large scale (in longitude) Modulated with the planet period Interaction= combination of the solar wind flow and the corotation of the plasma. Most intense on the morning side, but modulated by the planet period Sub-corotating radio arcs are also observed [Lamy et al.,2008]
from exoplanet, we could derive : • The revolution period of the planet • The inclination of the exoplanet's orbit (Hence, the mass of the exoplanet) • The rotation period of the exoplanet (Only way to obtain it for gazeous planets) • The magnetic field of the planet (at least the dipole component) • Information about how the planet and its star interact. Published in : S. Hess, P. Zarka, Modeling of the radio signature of the exoplanets orbital parameters, Astronomy and Astrophysics, 2011