Beaming Cone of Io-Controlled Jovian Decameter Radiation Derived From the JRMP9 Magnetic Field Model
Résumé
We investigate the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field B and its gradient ∇B in the source region. A previous study based on the O6 magnetic field model of Jupiter revealed that the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. The Jovian decameter radiation, like the other auroral radio emissions of the magnetized planets, is known to be produced by the cyclotron maser instability (CMI). In a plasma with axial symmetry, i.e., where B and ∇B are parallel, the maximum amplification of the waves is obtained for a particular value of the emergence angle relatively to the local magnetic field B. This angle is not constant anymore when B and ∇B are not parallel, so that the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. In this study, we use the new model of Jupiter's magnetic field based on Juno's first nine orbits, JRMP9, proposed by Connerney et al. [Geophys. Res. Lett., 45, 2590-2596, 2018], in order to analyze the geometry of the emission cone.