Energetic Neutral Atom (ENA) Imaging and In-Situ Energetic Particle Exploration of the Jovian Magnetosphere and Moon Environment from JUICE/PEP

Abstract

The Jovian Energetic Neutrals and Ions (JENI) Camera and the Jovian Energetic Electrons (JoEE) belong to the six-sensor suite Particle Environment Package (PEP) on board the JUICE mission. JENI is a combined ion and ENA camera with 90˚x120˚ Field-of-View and an energy range from a few keV to 110 keV for ENAs and 5 MeV for ions. Only one mission, Cassini, has captured ENA images of the Jovian system before during its distant flyby. Those images revealed emissions coming from the Europa neutral gas torus, but were too distant to resolve details on its spatial distribution and variability. The Juno mission has detected ENA emissions originating from both the Europa and also the Io torus, that indicate azimuthally asymmetric distributions. In ENA mode, JENI will image the Europa and Io tori, to investigate their spatial distribution and long-term variability providing global constraints to physical models of their sources. Although a predominant fraction of the ENAs from the tori originate from charge exchange between magnetospheric energetic ions and the neutral gas, a significant fraction may originate from charge exchange between the energetic ions and the ambient plasma in the tori. This opens up the intriguing possibility to also diagnose the plasma dynamics and distribution of the tori. JENI also targets the explosive recurrences of vast regions of heated plasma in the Jovian magnetotail (“injections”) that may be the engine behind the periodic radio emissions from rotating, magnetized planets, such as Saturn, Jupiter and perhaps even brown dwarfs. In ion mode, JENI will provide the detailed in-situ measurements of the energetic ion environment necessary to understand the physical heating and transport processes underlying the global context provided by the ENA images. JoEE is an electron spectrometer that near-simultaneously provide the energetic electron spectrum in multiple look directions over the energy range from 28 keV up to 2 MeV. JoEE’s prime objectives are to investigate the acceleration mechanisms of Jovian radiation belt electrons and their interaction with the Jovian moons. The Juno mission has recently made important electron measurements that provides useful guidance for deepening the JoEE objectives. In this presentation an overview is given of JENI and JoEE, with emphasis on the ENA observations and their expected science return. This includes imaging of the Europa and Io tori distribution and variability, quasi-periodic magnetospheric injections, and their relation to rotationally periodic radio emissions from planets and brown dwarfs.