Acceleration of protons at 32 Jovian radii in the outer magnetosphere of jupiter

Journal Article · Wed Mar 01 04:00:00 EST 1978 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA083iA03p01104· OSTI ID:7276648

Schardt, A W; McDonald, F B; Trainor, J H

During the inbound pass of Pioneer 10 A rapid tensold increase of the 0.2- to 5-MeV proton flux was observed at 32 R/sub j/ (Jovian radii). The total event lasted for 30 min and was made up of a number of superimposed individual events. At the time the spacecraft was in the outer magnetosphere about 7 R/sub j/ below the magnetic equator. Before and after the event the proton flux was characteristic of the low flux level normally encountered between crossings of the magnetic equator. Flux changes at different energies were coherent within 1 min, a time comparable to the time resolution of the data. Differential travel time would have led to a greater time difference if the sources had been further than 5-10 R/sub j/ from the spacecraft. The angular distributions were highly anisotropic with protons streaming toward Jupiter. A field-aligned dumbbell distribution was observed initially, and a pancake distribution just before the flux decayed to its preevent value. The alpha particle flux changes as rapidly as the proton flux but peaked at different times. The energetic electron flux behaved differently; it increased gradually throughout the period. This acceleration event was associated with a double crossing of a current sheet, most of the acceleration being coincident with the first crossing. The average shape of the proton energy spectrum (0.3-5 MeV) remained unchanged during the event and resembled the spectrum observed in the magnetodisk. A superposition of acceleration processes of this type is probably responsible for maintaining the energetic particle population around 30 R/sub j/ in the magnetosphere. Random fluctuations in the occurrence of acceleration events would explain the 10-50% flux changes during less than 15 min which were observed most of the time the Pioneer 10 and 11 spacecraft were in the outer Jovian magnetosphere.

• Research Organization: Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771
• OSTI ID: 7276648
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 83:A3; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ALPHA PARTICLES
ANGULAR DISTRIBUTION
ATMOSPHERES
BARYONS
CHARGED PARTICLES
DISTRIBUTION
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
ENERGY SPECTRA
FERMIONS
HADRONS
INTERPLANETARY MAGNETIC FIELDS
JUPITER PLANET
LEPTONS
MAGNETIC FIELDS
MEV RANGE
NUCLEONS
PLANETARY ATMOSPHERES
PLANETARY MAGNETOSPHERES
PLANETS
PLASMA ACCELERATION
PROTONS
SPECTRA