Probing Jupiter’s auroral radio sources with Juno

Jupiter is the major auroral radio source in our solar system, producing Jovian low-frequency radio emissions in a broad frequency range of 10 kHz to 40 MHz from both north and south polar regions of the planet. These sporadic nonthermal bursts have been monitored with the radio and plasma wave instrument (Waves) aboard the spinning Juno spacecraft in polar orbit about Jupiter since July 5, 2016. The Waves instrument is composed of one electric dipole antenna, one magnetic search coil sensor, and three on-board receivers that record the electric fields of waves from 50 Hz to 41 MHz and the magnetic fields of waves from 50 Hz to 20 kHz. Juno has three advantageous methods to determine the radio source locations and the beaming properties for the Jovian low-frequency radio emissions: (1) identifying emission frequency close to the local gyrofrequency at the source with in situ particle measurements through Juno's perijove surveys from pole to pole, (2) the spin-modulated spectral density recorded with Juno Waves to estimate the direction of arrival of incoming waves, and (3) with the aid of the Jovian radio beaming model, performing stereoscopic radio observations with Juno, Cassini, STEREO A, WIND, and Earth-based radio telescopes (e.g., LWA1 in New Mexico, USA, and NDA in Nançay, France) or investigating the statistical characteristics of Jovian radio occurrence by Juno. Because the three individual methods are self-consistent and complement each other, Juno observations are useful for determining the Jovian radio beam parameters and radio source locations, which can be traced along magnetic field lines onto Jupiter's atmosphere and further compared with the UV aurora taken by the Hubble Space Telescope. In this talk, we give a brief overview of early radio astronomy results from Juno, providing the recent results from these extended studies by means of the three methods.