EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-2050 In-Situ and Remote Observations of the Ring Current and Radiation Belt during JUICE Lunar Earth Gravity Assist Brandt Pontus C. https://orcid.org/0000-0002-4644-0306 1 Clark George 1 Mitchell Donald G. 1 Kollmann Peter https://orcid.org/0000-0002-4274-9760 1 Gkioulidou Matina 1 Regoli Leonardo https://orcid.org/0000-0002-7628-1510 1 Dialynas Kostas 2 Allegrini Frederic 3 Andre Nicolas 4 Jia Xianzhe https://orcid.org/0000-0002-8685-1484 5 Khurana Krishan https://orcid.org/0000-0002-2856-1171 6 Paty Carol https://orcid.org/0000-0001-8362-9880 7 Barabash Stanislav 8 Wurz Peter https://orcid.org/0000-0002-2603-1169 9 The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA Academy of Athens, Athens, Greece Southwest Research Institute, San Antonio, TX, USA Institut de Recherche en Astrophysique et PlanĂ©tologie, Toulouse, France University of Michigan, Ann Arbor, MI, USA University of California Los Angeles, Los Angeles, CA, USA University of Oregon, Eugene, OR, USA Swedish Institute of Space Physics, Kiruna, Sweden University of Bern, Bern, Switzerland 15 04 2026 2026 1 13 Copyright: © 2026 Pontus C. Brandt et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2050/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2050/egusphere-2026-2050.pdf

This report presents an overview of the observations and performance of the Jovian Energetic Neutrals and Ions (JENI) and the Jovian Energetic Electrons (JoEE) belonging to the Particle Environment Package (PEP) onboard the Jupiter Icy Moon Explorer (JUICE) during its Lunar-Earth Gravity Assist (LEGA) 19&ndash;23 August 2024. Observations from the Lunar and Earth flybys are presented and discussed. While the environment around the Moon was very quiet, the Earth flyby presented a characteristic, nearly symmetric recovery phase ring current with adiabatically increasing energies with decreasing distance to Earth, and butterfly pitch-angle distributions (PADs) at high L-shells transitioning to distributions rounded around 90&deg; pitch angle at lower L-shells. The electron radiational belt showed a double-structured outer zone, possibly from a fresh intensification, and the characteristic slot region created by loss through interactions with plasmaspheric hiss. On the outbound, JENI was operated as an Energetic Neutral Atom (ENA) camera and observed the energetic ions of the inner magnetosphere from 17.4 R<sub>E</sub> to 150 R<sub>E</sub>. During this period multiple intensifications were observed in the night side magnetosphere consistent with substorm injections. The LEGA observations provided useful data for further calibrating the sensors that overall showed a nominal performance.

 NASA Headquarters 80MSFC23F0077