Galactic cosmic-ray intensity to a heliocentric distance of 18 AU
Abstract
The paper reports observations to heliocentric radial distances of 8.6 and 18.4 AU with Pioneer 11 and Pioneer 10 respectively. During a seven year period from March 1972 to March 1979, the galactic cosmic-ray intensity of greater than 80 MeV, as measured by detectors on Pioneers 10 and 11, exhibited aperiodic temporal variations by about a factor of 2 and on a time scale of the order of a year, and quasipersistent cyclic variations of a 26 day period and an amplitude of a few percent. For protons of an energy greater than 80 MeV, there is a fairly consistent heliocentric radial gradient of +2.1 (plus or minus 0.3%) per AU in integral intensity until 1978 April-May, at which time a substantial disruption of the distribution of cosmic rays in the heliosphere occurred.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1980
- DOI:
- 10.1086/158034
- Bibcode:
- 1980ApJ...238..763V
- Keywords:
-
- Cosmic Rays;
- Galactic Radiation;
- Interplanetary Medium;
- Radiant Flux Density;
- Radiation Distribution;
- Latitude;
- Pioneer 10 Space Probe;
- Pioneer 11 Space Probe;
- Spaceborne Astronomy;
- Spectroheliographs;
- Time Dependence;
- Space Radiation