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Radial and Latitudinal Gradients of Anomalous Cosmic-Ray Oxygen and Helium and Galactic Cosmic Rays in the Outer Heliosphere

Cummings, A. C. and Stone, E. C. and McDonald, F. B. and Webber, W. R. and Lal, N. (1987) Radial and Latitudinal Gradients of Anomalous Cosmic-Ray Oxygen and Helium and Galactic Cosmic Rays in the Outer Heliosphere. In: Proceedings of the 21st International Cosmic Ray Conference. Vol.3. , Nakau, Russia, pp. 417-420.

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We have used measurements from instruments on Voyagers 1 and 2 and Pioneer 10 to derive simultaneous latitudinal and radial gradients of anomalous cosmic-ray helium and oxygen and galactic cosmic rays during the latter part of 1986. We find that the negative latitudinal gradients that first appeared in 1985 when Voyager 1 reached heliolatitudes in excess of the current sheet continue to be observed, with an increased magnitude probably related to the decreasing tilt of the current sheet. The sign of this gradient is opposite to that reported during the last solar cycle when the solar magnetic field polarity was reversed, as predicted by propagation models in which curvature and gradient drifts are important. Although during the 1985-1986 time period radial gradients in the outer heliosphere appeared to decrease, the ratios of the radial and latitudinal gradients remained similar for both anomalous and galactic particles as predicted by drift theory. These observations indicate that the particles move inward preferentially at low latitudes from the heliospheric boundary during the current phase of the solar cycle.

Item Type:Book Section
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URLURL TypeDescription
Cummings, A. C.0000-0002-3840-7696
Stone, E. C.0000-0002-2010-5462
Additional Information:© INR. Provided by the NASA Astrophysics Data System. This work was supported in part by NASA under contract NAS-7-918 and grant NGR-05-002-160.
Group:Space Radiation Laboratory
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Space Radiation Laboratory1987-11
Record Number:CaltechAUTHORS:20140512-142436514
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45700
Deposited By: Joy Painter
Deposited On:12 May 2014 21:29
Last Modified:20 Feb 2020 14:33

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