Daniel Santos-Costa

Observations of MeV electrons in Jupiter's innermost radiation belts and polar regions by the Juno radiation monitoring investigation: Perijoves 1 and 3

Junos “Perijove 1” (27 August 2016) and “Perijove 3” (11 December 2016) flybys through the innermost region of Jupiters magnetosphere (radial distances 5xa0MeV and >10xa0MeV electron fluxes derived from these measurements provide valuable constraints for models of relativistic electron environments in the inner radiation belts. Several intense bursts of high-energy particle counts were also observed by the Advanced Stellar Compass in polar regions outside the radiation belts.

A Heavy Ion and Proton Radiation Belt Inside of Jupiter's Rings

Energetic charged particle measurements by the JEDI instrument onboard Juno have revealed a radiation belt of hundreds of keV ions up to the atomic mass of sulfur, located between Jupiterâs rings and atmosphere. Proton energy spectra display an unusual intensity increase above 300keV. We suggest that this is because charge exchange in Jupiterâs neutral environment does not efficiently remove ions at such high energies. Since this innermost belt includes heavy ions, it cannot be exclusively supplied by cosmic ray albedo neutron decay (CRAND), which is an important source at Earth and Saturn but only supplies protons and electrons. We find indications that the stripping of energetic neutral atoms (ENAs) in Jupiterâs high atmosphere might be the ion source. Since the stripped off electrons are of low energy, this hypothesis is consistent with observations of the ratio of energetic electrons to ions being much less than 1.

First look at Jupiter's synchrotron emission from Juno's perspective

Since August 2016, measurements of Jupiters microwave emissions at six wavelengths ranging from 1.3 cm to 50 cm have been made with the Juno Microwave Radiometer (MWR). In this paper, we introduce the first systematic set of in-situ observations of synchrotron radiation in a polar plane while describing the modeling approach we use to analyze this data (collected August 27th, 2016). Time series of brightness profiles at all six frequencies present similarities that are explained by the presence of known regions of intense synchrotron radiation. Our model predictions, though limited for now to the total intensity of the radiation, reproduce (qualitatively) the observation of temporal variations and allow to disentangle the synchrotron emission from the atmospheric emission. The discrepancies seen between the data and simulations confirm that physical conditions close to Jupiter affecting synchrotron emission (electron energy spectra, pitch-angle distributions, and the magnetic environment) are different than we anticipated.