Radial diffusion in the Uranian radiation belts: inferences from satellite absorption loss models

Journal Article · Tue Oct 31 23:00:00 EST 1989 · Journal of Geophysical Research; (USA)

DOI:https://doi.org/10.1029/JA094iA11p15077· OSTI ID:6990801

Hood, L L ^[1]

---

1. Lunar and Planetary Laboratory, University of Arizona, Tucson (US)

Phase space density profiles for protons and electrons with first invariants {mu}{le}100 MeV/G (integral invariants {ital K}=0.3 and 0.6 G{sup 1/2} {ital R}{sub {ital U}}) previously derived from measurements by the low energy charged particle (LECP) detector on Voyager 2 during the 1986 Uranus encounter are analyzed using solutions of the time-averaged radial diffusion equation in a dipolar magnetic field. These profiles are selected for their consistency with an absence of local sources of particles. A loss model consisting of absorption by the major inner satellites Miranda, Ariel, and Umbriel is assumed and the corresponding form of the time-averaged radial diffusion coefficient {ital D}({ital L}) (taken to be of the form {ital D}({ital L})={ital D}{sub 0}{ital L}{sup {ital n}}, where {ital n} is an integer) is determined by a minimum-variance fit to the phase space density profiles. Satellite macrosignatures present in the experimentally derived profiles are approximately reproduced in several cases lending credence to the loss model and indicating that magnetospheric distributed losses are not as rapid as satellite absorption near the minimum satellite {ital L} shells for these particles. The latter inference implies an upper limit of approximately 10 cm{sup {minus}3} for the neutral hydrogen number density near the orbit of Ariel, based on a comparison of charge exchange lifetimes with the calculated satellite absorption lifetimes. The preferred forms for {ital D}({ital L}) are characterized by a low-order {ital L} dependence ({similar to}{ital L}{sup 3}{minus}{ital L4}) and an amplitude ({ital D}{sub 0}{congruent}10{sup {minus}11}--10{sup {minus}10} {ital R}{sup 2}{sub {ital U}} {sup {minus}1}). The inferred {ital L} dependence is least consistent with terrestrial-type diffusion mechanisms including magnetic impulses and electrostatic field fluctuations of purely magnetospheric origin.

• OSTI ID: 6990801
• Journal Information: Journal of Geophysical Research; (USA), Journal Name: Journal of Geophysical Research; (USA) Vol. 94:A11; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
BARYONS
DIFFUSION
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HADRONS
HYDROGEN
INSTABILITY
LEPTONS
NONMETALS
NUCLEONS
PLANETARY ATMOSPHERES
PLANETARY IONOSPHERES
PLANETARY MAGNETOSPHERES
PLANETS
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PROTONS
RADIATION BELTS
SATELLITES
TRAPPED-PARTICLE INSTABILITY
URANUS PLANET