Galactic cosmic-ray intensity to a heliocentric distance of 18 AU. Progress report. [Pioneer 10 and 11]

Technical Report · Wed Aug 01 04:00:00 EDT 1979

OSTI ID:5150499

Van Allen, J A

An updated report is given of observations of galactic cosmic ray intensity to heliocentric radial distances of 8.6 and 18.4 AU with Pioneer 11 and Pioneer 10, respectively. Solar activity via the magnetic structure of the interplanetary medium continues to modulate the intensity out to the greatest distance reached thus far. During the period 1972-1979, aperiodic temporal variations of intensity by about a factor of two and on a time scale of the order of a year are observed as are quasi-persistent cyclic variations of 26-day period and amplitude of a few percent. The latter are associated with fast-slow solar wind streams, not with toward-away magnetic field sectors. For protons of energy E/sub P/ > 80 MeV, there is a fairly consistent heliocentric radial gradient of +2.1 (+- 0.3) percent per AU in intensity until April-May 1978, at which time a substantial disruption of the distribution of cosmic rays in the heliosphere occurred. The radius of the heliosphere is estimated to be of the order of 80 AU.

• Research Organization: Iowa Univ., Iowa City (USA). Dept. of Physics and Astronomy
• OSTI ID: 5150499
• Report Number(s): AD-A-076605
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
640104 -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BARYONS
COSMIC PROTONS
COSMIC RADIATION
COSMIC RAY FLUX
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRONS
INTERACTIONS
INTERPLANETARY MAGNETIC FIELDS
INTERPLANETARY SPACE
IONIZING RADIATIONS
MAGNETIC FIELDS
MEV RANGE
NUCLEONS
PIONEER SPACE PROBES
PRIMARY COSMIC RADIATION
PROTONS
RADIATION FLUX
RADIATIONS
SOLAR ACTIVITY
SOLAR WIND
SPACE
SPACE VEHICLES
VARIATIONS