Jovian Synchrotron Observations From The Juno Microwave Radiometer

The Juno Microwave Radiometer (MWR) is in a unique position to measure the synchrotron emission from Jupiter’s inner radiation belts. Juno is a spinning spacecraft in a highly eccentric polar orbit about Jupiter, with perijoves at about 5000 km above the cloudtops. From this unique vantage point, the Juno Microwave Radiometer (MWR) has measured the radio emission in 6 channels, at wavelengths ranging from approximately 1.4 to 50 cm, with 100 ms sampling throughout each spin of the spacecraft, since the first science pass in August of 2016. Synchrotron emission is emitted in a narrow cone about the electron’s direction of motion, so Earth-based observations are limited by our equatorial vantage point. The Juno data set provides a remarkable view of the Jovian synchrotron emission over a wide range of viewing angles, from inside the radiation belts.  While the MWR synchrotron data set is unprecedented, the size and variety of the data set also make analysis complex. We have therefore begun by extracting a limited subset of the data. For each channel during each perijove pass, we have determined the peak emission observed in the equatorial lobe and in the high-latitude lobes.  Using these data, we determine the spectral index of the synchrotron emission as a function of frequency, from 0.6 GHz to 22 GHz.  Results will be compared with models to examine the energy distribution of electrons.