Heliospheric intensity gradients of the anomalous He/sup 4/ and the galactic cosmic-ray components

Journal Article · Tue Jun 01 04:00:00 EDT 1982 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/183805· OSTI ID:5027923

McKibben, R B; Pyle, K R; Simpson, J A

Measurements with the Pioneer 10 and 11 spacecraft over the radial range from 1 to approx.25 AU during the period 1972--1981 show that at solar minimum (1972--1977) the radial gradient for the anomalous helium component (He(A)) in the energy range from 11 to 20 MeV n/sup -1/ is approx.14% AU/sup -1/, significantly smaller than predicted for either charge state (He/sup +/(A) or He/sup + +/(A)) of the component based on the observed spectrum and the assumptions of conventional solar modulation for particles propagating inward from the heliospheric boundary. It is shown that, although the He(A) dissapeared at 1 AU by 1979 as a result of increasing solar modulation, it remained present in the outer solar system (R> or approx. =20 AU) into 1980, when the solar polar magnetic fields were observed to reverse and solar activity was near its maximum levels. By 1981, He(A) had essentially dissapeared at Pioneer 10 (Rroughly-equal24 AU) and the radial gradient had decreased to levels consistent with those expected for galactic helium with a normal modulated spectrum.

• Research Organization: Enrico Fermi Institute, University of Chicago
• OSTI ID: 5027923
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Journal Name: Astrophys. J., Lett. Ed.; (United States) Vol. 257:1; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
BARYONS
COSMIC NUCLEI
COSMIC PROTONS
COSMIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FLUIDS
GASES
HADRONS
HELIUM
IONIZING RADIATIONS
NONMETALS
NUCLEI
NUCLEONS
PIONEER SPACE PROBES
PROTONS
RADIATIONS
RARE GASES
SPACE VEHICLES
VEHICLES