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GEOPHYSICAL RESEARCH LETTERS, VOL. 22, NO. 4, PAGES 333–336, 1995

Measurement of Anomalous Cosmic Ray Oxygen at Heliolatitudes ∼25° to ∼64°

L. J. Lanzerotti

AT&T Bell Laboratories, Murray Hill, NJ.


C. G. Maclennan

AT&T Bell Laboratories, Murray Hill, NJ.


R. E. Gold

Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD.


T. P. Armstrong

Department of Physics, University of Kansas, Lawrence.


E. C. Roelof

Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD.


S. M. Krimigis

Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD.


G. M. Simnett

University of Birmingham, UK.


E. T. Sarris

University of Thrace, Xanthi, Greece.


K. A. Anderson

Space Sciences Laboratory, University of California, Berkeley.


M. Pick

Observatoire de Paris, Meudon, France.


R. P. Lin

Space Sciences Laboratory, University of California, Berkeley.


Abstract

We report measurements of the oxygen component (0.5 - 22 MeV/nucl) of the interplanetary cosmic ray flux as a function of heliolatitude. The measurements reported here were made with the Wart telescope of the HI-SCALE low energy particle instrument on the Ulysses spacecraft as the spacecraft climbed from ∼24° to ∼64° south solar heliolatitude during 1993 and early 1994. As a function of heliolatitude, the O abundance at 2-2.8 MeV/nucl drops sharply at latitudes above the heliospheric current sheet. The oxygen spectrum obtained above the current sheet has a broad peak centered at an energy of ∼2.5 MeV/nucl that is the anomalous O component at these latitudes. There is little evidence for a latitude dependence in the anomalous O fluxes as measured above the current sheet. Within the heliospheric current sheet, the O measurements are composed of both solar and anomalous origin particles.

Received 22 August 1994; accepted 2 November 1994.

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Citation: Lanzerotti, L. J., et al. (1995), Measurement of Anomalous Cosmic Ray Oxygen at Heliolatitudes ∼25° to ∼64°, Geophys. Res. Lett., 22(4), 333–336.