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Published February 15, 1995 | Published
Journal Article Open

Anomalous Cosmic Ray Oxygen Gradients Throughout the Heliosphere

Abstract

We have used data from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), Ulysses, Voyager 1, Voyager 2, and Pioneer 10 spacecraft to determine the radial and latitudinal gradients of anomalous cosmic ray oxygen at 10 MeV/nuc during the last half of 1993. These five spacecraft cover radial distances from 1 AU (SAMPEX) to 58 AU (P10) and latitudes to 41 deg S (Ulysses) and 32 deg N (V1). We find that the radial gradient is a decreasing function of radial distance, approximately r-n, with n = 1.7 +/- 0.7. The large-scale radial gradient between the inner and outer heliosphere is much smaller than it was during the last solar minimum period in approximately 1987. The latitudinal gradient is small and positive, 1.3 +/- 0.4 %/deg, as opposed to the large and negative latitudinal gradients found during 1987, but similar to the small positive latitudinal gradient measured during 1976 for anomalous cosmic ray helium. These observations confirm that effects of curvature and gradient drift in the large scale magnetic field of the Sun are important for establishing the three-dimensional intensity distributions of these particles in the heliosphere during periods of solar minimum conditions

Additional Information

© 1995 American Geophysical Union. Paper number 9401GL03343. This work was supported by NASA under contracts NAS7-918, NAS5-30704, JPL contract 958748, and Agreement 26979B. This work was also supported by the MPG and BMFT under grant numbers Ol0Nl990, 500N87037, 500C90021, and 500N91050.

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August 20, 2023
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