A source of very energetic oxygen located in Jupiter’s inner radiation belts

Abstract

A local charged particle source in Jupiter’s inner radiation belts generates oxygen ions of cosmic ray energies.

Ganymede's Radiation Cavity and Radiation Belts

“…Rising PSD means that the radiation belt cannot be simply supplied through steady inward transport of particles. If the belt is somewhat steady, local sources of some kind are needed to explain PSD (e.g., Roussos, 2022). If the belt is transient, it is possible that peak is a result of an initially falling profile that was eroded around L ≈ 1.6 (e.g., Kollmann, Clark, et al., 2021).…”

Pitch Angle Distribution of MeV Electrons in the Magnetosphere of Jupiter

“…True field‐aligned auroral beams likely show the signature of high‐latitude auroral acceleration mechanisms. A scattered beam may however be the signature of one of the 4 following physical phenomena in the middle and outer magnetosphere of Jupiter: A scattered beam can be a true auroral beam which has been scattered over time by an unknown process at the M‐shell where the auroral beam was produced, or may have been scattered and accelerated during adiabatic inward radial transport The pitch angle dependency of the loss rate associated with moon absorption can create field‐aligned distributions (Long et al., 2022), as seen for energetic ions close to Jupiter (Roussos et al., 2022) The loss or cooling of energetic electrons due to interaction with equatorial neutral gas or cold plasma populations may also create energetic electron field‐aligned distributions (Clark et al., 2014), although physics‐based modeling indicates that these processes are likely negligible for energetic electrons in the Jovian magnetosphere (Nénon et al., 2017) Outward adiabatic radial transport with conservation of the two first adiabatic invariants of energetic electrons can create field‐aligned distributions (e.g., Rymer et al., 2008). …”

“…A scattered beam can be a true auroral beam which has been scattered over time by an unknown process at the M-shell where the auroral beam was produced, or may have been scattered and accelerated during adiabatic inward radial transport 2. The pitch angle dependency of the loss rate associated with moon absorption can create field-aligned distributions (Long et al, 2022), as seen for energetic ions close to Jupiter (Roussos et al, 2022) 3. The loss or cooling of energetic electrons due to interaction with equatorial neutral gas or cold plasma populations may also create energetic electron field-aligned distributions (Clark et al, 2014), although physics-based modeling indicates that these processes are likely negligible for energetic electrons in the Jovian magnetosphere (Nénon et al, 2017) 4.…”

Comprehensive Observations of Magnetospheric Particle Acceleration, Sources, and Sinks (COMPASS): A Mission Concept to Jupiter’s Extreme Magnetosphere to Address Fundamental Mysteries in Heliophysics

“…However, basic questions still remain unanswered, e.g., the moons Io and Europa exhibit geologic activity (e.g., Roth et al, 2014), but it is unclear which of them is the major oxygen source for the radiation belts. In addition to the moons, the Jovian ring system might indirectly provide heavy ions when already existing radiation causes spallation of atomic nuclei (Roussos et al, 2022). While moons, their associated gas tori, and rings provide particles to the radiation belts, these objects also simultaneously remove particles through absorption or cool them through Coulomb collisions (Clark et al, 2014, Nénon et al, 2018.…”

“…Recent results underscore that the high energies found at Jupiter open the window to observe physics that is otherwise only accessible indirectly. Heavy ion distributions deep in the radiation belts reveal a local source of >50 MeV/nucleon oxygen (Roussos et al, 2022)-the physics of which cannot be studied in the Terrestrial magnetosphere but appear to have stronger parallels to stellar or astrophysical acceleration processes (e.g., Doyle et al, 2021). Finally, Jupiter is so massive that of all planets within our reach it is thought to accumulate the highest amounts of dark matter.…”