Features of emission cone of Jovian decameter radiation and observation of Jupiter's magnetic field by JUNO
Résumé
A new magnetic field model for Jupiter, based on Juno's first nine orbits observations, JRM09, was recently proposed by Connerney et al. [Geophys. Res. Lett., 45, 2590-2596, 2018]. We use this model to 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, and we compare the results to those obtained several years ago using older models (O6, VIP4, VIT4 and VIPAL). The JRM09 model confirms the former results: the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. The same assumptions were made as in the previous studies: the Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI) in a plasma where B and ∇B are not parallel. As a consequence, the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. This flattening appears to be more important for the northern emission (34.8%) than for the southern emission (12.5%) probably due to the fact that the angle between the directions of B and ∇B is greater in the North (∼ 10∘) than in the South (∼ 4∘).