If you've seen one magnetosphere, you haven't seen them all: energetic particle observations in the Saturn magnetosphere
The Goddard Space Flight Center/University of New Hampshire Pioneer 11 Cosmic ray experiment, with its ability to measure precisely proton and electron energy spectra and angular distribution and to identify heavier ions, was especially well suited for studying Saturn's magnetosphere. Pioneer 11 passed through the subsolar and dawn magnetospheres while a solar cosmic ray event was in progress and the solar wind pressure was enhanced. Energetic electrons (>0.16 MeV) and protons (E>0.2 MeV) were identified as major magnetospheric constituents, along with trace amounts of alpha particles (>0.65 MeV/nuc) and possible heavier nuclei. Three distinct regions were found inside the magnetopause: (1) an outer magnetosphere between 7.5 Saturn radii (R/sub S/) and the magnetopause at 17.3 R/sub S/ inbound and 30 to 40 R/sub S/ outbound, (2) a slot region between 4 and 7.5 R/sub s/ which is dominated by the absorption due to three of Saturn's satellites and (3) an inner region with an intense proton and high-energy electron flux which stops abruptly at the outer edge of the A ring. The population in the outer magnetosphere consisted of solar cosmic rays (protons and alpha particles) and trapped protons and electrons. The access of solar cosmic rays to at least 9 R/sub S/ is interpreted in terms of an open magnetotial configuration. The phase space density shows that the trapped particles were diffusing inward, and the alpha-to-proton ratio at 0.65 MeV/nuc suggests that most of the protons must be of Saturn origin. The outer magnetosphere was found to be variable, presumably in response to changes in solar wind conditions. This variability was reflected not only in the particle fluxes, but most dramatically in changes of their pitch angle distributions. In the slot region the electron and proton fluxes are reduced by amounts that are strongly energy dependent.
- Research Organization:
- Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771
- OSTI ID:
- 6734657
- Journal Information:
- J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 85:A11; ISSN JGREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALPHA PARTICLES
ANGULAR DISTRIBUTION
ATMOSPHERES
BARYONS
CHARGED PARTICLES
DISTRIBUTION
ELECTRONS
ELEMENTARY PARTICLES
ENERGY SPECTRA
FERMIONS
HADRONS
LEPTONS
MAGNETOPAUSE
NUCLEONS
PARTICLE SOURCES
PIONEER SPACE PROBES
PLANETARY ATMOSPHERES
PLANETARY MAGNETOSPHERES
PLANETS
PROTONS
RADIATION SOURCES
SATURN PLANET
SOLAR ACTIVITY
SOLAR WIND
SPACE VEHICLES
SPECTRA
TRAPPED ELECTRONS
TRAPPED PROTONS
VEHICLES