Loss of Energetic Ions Comprising the Ring Current Populations of Jupiter's Middle and Inner Magnetosphere

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Abstract

The low-altitude, polar orbit of the Juno mission allows the Jupiter Energetic Particle Detector Instrument to view into, and resolve, the loss cone of energetic ions comprising the low-altitude extension of Jupiter's ring current ions. For regions mapping from just inside Ganymede's orbit to well beyond Ganymede's orbit, energetic ions (>50 keV H+ and >130 keV Oxygen and Sulfur ions) are strongly scattered into the loss cone and lost to the magnetosphere at the “strong diffusion limit” at essentially all times. We conclude, by arguing against magnetic curvature scattering, that the cause is waves, perhaps associated with Alfvénic variations previously documented in this equatorial region. Scattering is generally weak or nonexistent near the orbits of the moons Europa and Io, except for the regions just downstream of the corotating plasmas. For Io, we sometimes observe moderate, but not saturated, scattering within roughly 60° downstream. Significantly, scattering is weak or nonexistent just upstream of Io's position, an asymmetry echoed in some previous wave observations. A preliminary accounting of the total (longitude-averaged) scattering losses near Io's orbit yields loss rates of order 4%–5% of the strong diffusion limit for H+ and 5%–7% for heavy ions (O + S). We conclude that near Io's orbit, charge exchange losses likely dominate over scattering losses for heavy ions and for the lower energy H+ ions (roughly <200 keV).

Original languageEnglish (US)
Article numbere2022JA030293
JournalJournal of Geophysical Research: Space Physics
Volume127
Issue number5
DOIs
StatePublished - May 2022

Bibliographical note

Funding Information:
We are grateful to NASA and contributing institutions that played critical roles in making the Juno mission possible, and particularly those numerous individuals at The Johns Hopkins University Applied Physics Laboratory (JHU/APL) who developed the JEDI instrument. We are grateful for Lead Engineer Charles E Schlemm and David B. LaVallee for their continued support of JEDI operations. We are grateful to JHU/APL's Lawrence E. Brown and James M. Peachey for their roles in developing and maintaining the data flow and display software used here. NASA's New Frontiers Program funded much of this work for Juno via subcontract with the Southwest Research Institute. The work of M. Imai was supported by the JSPS KAKENHI Grant No. JP20K22371. Q. Nénon acknowledges support from the European Space Agency (ESA) as an ESA Research Fellow.

Funding Information:
We are grateful to NASA and contributing institutions that played critical roles in making the Juno mission possible, and particularly those numerous individuals at The Johns Hopkins University Applied Physics Laboratory (JHU/APL) who developed the JEDI instrument. We are grateful for Lead Engineer Charles E Schlemm and David B. LaVallee for their continued support of JEDI operations. We are grateful to JHU/APL's Lawrence E. Brown and James M. Peachey for their roles in developing and maintaining the data flow and display software used here. NASA's New Frontiers Program funded much of this work for Juno via subcontract with the Southwest Research Institute. The work of M. Imai was supported by the JSPS KAKENHI Grant No. JP20K22371. Q. Nénon acknowledges support from the European Space Agency (ESA) as an ESA Research Fellow.

Publisher Copyright:
© 2022 The Johns Hopkins University Applied Physics Laboratory. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Keywords

  • Jupiter
  • energetic particles
  • losses
  • magnetosphere
  • precipitation
  • ring current

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