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Energetic Oxygen and Sulfur Ions in the Jovian Magnetosphere


Gehrels, Neil (1982) Energetic Oxygen and Sulfur Ions in the Jovian Magnetosphere. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/QBH7-KH81.


Observations of 1 to 20 MeV/nuc oxygen, sodium, and sulfur ions in the Jovian magnetosphere are reported. Measurements made by the Cosmic Ray Subsystem on Voyager 1 and 2 are used to calculate abundances and energy spectra in the region from 5 to 20 Jovian radii (RJ). The phase space density of the oxygen ions calculated from the spectra has a positive radial gradient between 6 and 17 RJ, indicating an inward diffusive flow. The diffusion coefficient upper limit at 9 RJ is ~10-5s-1. This limit, combined with the analysis of Voyager plasma observations by Siscoe et al. [1981], implies an upper limit to the mass loading rate near Io of ~1028 ions/s.

The energetic oxygen lifetime is within an order of magnitude of the strong pitch-angle diffusion lifetime in this region, with the largest total number of particles lost between 7.5 and 12.5 RJ. It is shown that the losses are not due to geometric absorption by Io, absorption by dust grains, or energy loss in the plasma of the inner magnetosphere, and it is therefore postulated that the primary loss mechanism is pitch-angle scattering into the loss cone.

The power delivered to the Jovian atmosphere by oxygen and sulfur ions with magnetic moments greater than 70 MeV/nuc-G (E≳0.3 MeV/nuc at 10 RJ, scattered into the loss cone between 6 and 17 RJ, is ~5x1012 W; a power comparable to the ~1.2x1013 W required to produce the auroral emission observed by the ultraviolet spectrometer on Voyager [Broadfoot et al., 1981]. The measured dependence of the input power on magnetic moment threshold indicates that additional power is contributed by oxygen and sulfur ions with magnetic moments less than 70 MeV/nuc-G. Since most of the particles are lost between 7.5 and 12.5 RJ, the latitudinal zone in which the most energy is deposited in the atmosphere is ~67° to ~71°.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Jupiter; Magnetosphere
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Awards:Caltech Distinguished Alumni Award, 2016
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Stone, Edward C.
Group:Space Radiation Laboratory, Caltech Distinguished Alumni Award
Thesis Committee:
  • Stone, Edward C. (chair)
  • Pine, Jerome
  • Barnes, Charles A.
  • Yung, Yuk L.
Defense Date:11 September 1981
Non-Caltech Author Email:neil.gehrels (AT)
Funding AgencyGrant Number
Record Number:CaltechETD:etd-04142009-144756
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1389
Deposited By: Imported from ETD-db
Deposited On:15 Apr 2009
Last Modified:22 Jul 2021 18:14

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