High Latitude Zones of GeV Heavy Ions at the Inner Edge of Jupiter's Relativistic Electron Belt. Issue 5 (25th May 2021)

• Record Type: Journal Article
• Authors: Becker, Heidi N.; Alexander, James W.; Connerney, John E. P.; Brennan, Martin J.; Guillaume, Alexandre; Adumitroaie, Virgil; Florence, Meghan M.; Kollmann, Peter; Mauk, Barry H.; Bolton, Scott J.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-25
• Subjects: heavy ion -- high energy -- Juno -- Jupiter -- ring -- stellar reference unit; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2020JE006772
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: Juno has discovered signatures of a high energy heavy ion population (>100 MeV/nucleon) within the inner edge of Jupiter's relativistic electron belt. The particles were detected in narrow zones in the high‐latitude lobes of the synchrotron emission region, a location never explored by prior spacecraft (∼31°–46° magnetic latitude; radial distances 1.12–1.41 Jovian radii, M‐shells 1.5–2.37). The population was revealed by extremely high signal ionization signatures seen in images collected by Juno's Stellar Reference Unit star camera (equivalent to 0.2–0.7 MeV of deposited energy per pixel). Signature morphology indicates a population of GeV ions ( Z > 1) with atomic mass as high as sulfur, although species with 2 ≤ Z ≤ 8 potentially account for all of the signatures. The detections have occurred while the spacecraft is magnetically connected to Jupiter's halo and gossamer rings, but not while it is connected to the main ring; similar to equatorial observations of GeV carbon and sulfur ions by the Galileo Probe. We find that the particles reside on magnetic drift shells that suggest they are stably trapped within Jupiter's magnetosphere. Because the cosmic ray albedo neutron decay mechanism can only produce protons and electrons, it cannot be the source of this trapped Z > 1 ion population; other galactic cosmic ray origins are suspected. Inward radial transport of tens of keV heavy ions from the outer magnetosphere is another potential source. Plain Language Summary: The Juno spacecraft orbits Jupiter closer than any prior spacecraft, skimming the inner edges of its severe radiation belts during science flybys. An unexpected population of ions has been found during Juno's brief high‐latitude encounters with the innermost electron belt. No other mission has explored this region. The population reveals itself as very bright noise signatures, like static on a television screen, in images from the spacecraft navigation camera. The ions are moving at close to light speed and may be composed of a combination of elements as light as helium or as heavy as sulfur. These are the highest energy particles detected by Juno. If encountered in great numbers, such ions are capable of causing spacecraft computer errors as well as damage to spacecraft electronics. Knowledge of the locations of these ion zones is important for the safe design of future missions to Jupiter and for understanding how radiation belts form around giant planets. Key Points: Juno is the first spacecraft to explore the inner edge of Jupiter's electron radiation belt at high latitudes Signatures of >100 MeV/nucleon ions with atomic mass heavier than hydrogen are observed in this region The ions are seen on magnetic field lines connected to Jupiter's halo and gossamer rings but not on field lines connected to the main ring