Energetic atomic and molecular ions in Saturn's magnetosphere

Journal Article · Mon Oct 31 23:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA088iA11p08905· OSTI ID:5015886

Hamilton, D C; Brown, D C; Gloeckler, G; Axford, W I

We present observations and anlysis of the composition, energy spectra and spatial distribution of energetic ions (> or approx. =0.2 MeV/nucleon) in Saturn's magnetosphere outside of approx.4 R/sub S/. Our results are based on data from the low-energy particle telescope (LEPT), one of the two sensors of the low-energy charged particle (LECP) experiment on Voyager 1 and 2. The major species, in order of abundance, are H, H/sub 2//sup +/, He, H/sub 3//sup +/, C, and O. The energy spectra of the magnetospheric ions are typically very soft (..gamma..approx.6-7), with an apparent cutoff in energy/charge at 1--2 MeV/e. From the abundance ratios we conclude that the energetic He, C, and O ions have a solar wind origin. The molecular hydrogen ions H/sub 2//sup +/, and H/sub 3//sup +/ probably originate from Saturn's upper ionosphere. The protons can originate from the solar wind, the ionosphere or the hydrogen atom torus in Saturn's outer magnetosphere. The local H/sup +/ sources apparently were dominant at the time of Voyager 1 encouter, but the solar wind may also have been an important source at the time of Voyager 2. To explain the fact that the energetic heavy ions (Z> or =6, E> or approx. =0.2 MeV/nucleon) are apparently of solar wind origin, an acceleration process that favors ions with small mass/charge ionized solar wind particles even though singly or doubly charged local ions (e.g. O/sup +/, O/sup + +/, N/sup +/, etc.) have been observed to be much more abundant in the low-energy magnetospheric plasma. Energization may involve a two-step process of electrostatic iacceleration in the tail region combined with inward radial diffusion. The fluxes of all species decreased inside the orbit of Dione and were nearlly wiped out in the ''slot'' region within the orbit of Tethys.

• Research Organization: Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742
• OSTI ID: 5015886
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:A11; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ATMOSPHERES
ATOMIC IONS
CHARGED PARTICLES
CHARGED-PARTICLE PRECIPITATION
ENERGY SPECTRA
ION DENSITY
IONIC COMPOSITION
IONS
MOLECULAR IONS
PLANETARY ATMOSPHERES
PLANETARY MAGNETOSPHERES
PLANETS
PLASMA ACCELERATION
SATURN PLANET
SOLAR ACTIVITY
SOLAR WIND
SPACE VEHICLES
SPECTRA
VEHICLES
VOYAGER SPACE PROBES