Jupiter's Innermost Radiation Belts from Juno Measurements
Abstract
The region inward of Europa's orbit shows the highest energetic ion intensities in Jupiter's magnetosphere and therefore offers a testbed to study transport and acceleration processes to high energies. These inner radiation belts have not been extensively sampled by earlier missions. Also with Juno, studying these belts remains challenging because the intensities are in parts too high to be measured reliably and also because Jupiter's complex and asymmetric magnetic field makes it difficult to map the measurements in a way different orbits can be compared fairly.
The JEDI and JADE instruments are able to sample the ion distribution in the innermost belt from the ionospheric population (showing at tens of eV due to the spacecraft motion) up to tens of MeV. The spectrum is a power law that is featureless at low energies but peaks in case of protons around 1 MeV, which is unusual, after which it cuts off. A phase space density analysis of the radial ion distribution suggests that there is either a local source process or that the distribution is not in steady state. We study the different candidate processes that may form the inner radiation belt (energetic neutral atom stripping and radial diffusive transport). As Jupiter's innermost belt is exposed to neutral material from Jupiter's exosphere and the ring halo inward of the main ring, losses resulting from the interaction with this material (energy loss and charge exchange) and their competition with the sources determine the shape and amplitude of the observed spectra. The results will be compared with the innermost radiation belt of Saturn that was found during the last phase of the Cassini mission. Also Saturn's innermost belt is continuously interacting with relatively high neutral material densities. The main difference is its source process (CRAND) that exclusively provides protons and electrons, while at Jupiter we also find oxygen and sulfur ions that are transported from the magnetosphere.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM33C3210K
- Keywords:
-
- 2756 Planetary magnetospheres;
- MAGNETOSPHERIC PHYSICS;
- 2774 Radiation belts;
- MAGNETOSPHERIC PHYSICS;
- 2780 Solar wind interactions with unmagnetized bodies;
- MAGNETOSPHERIC PHYSICS;
- 2784 Solar wind/magnetosphere interactions;
- MAGNETOSPHERIC PHYSICS