The Evolution of the Anomalous Cosmic Ray Oxygen Spectra From 1995 to 1998: Ulysses Observations |
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Authors: | B Heber E Keppler RG Marsden C Tranquille B Blake M Fränz |
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Institution: | (1) Max-Planck-Institute für Aeronomy, Katlenburg-Lindau, Germany;(2) Space Science Department of ESA, ESTEC, Noordwijk, The Netherlands;(3) The Aerospace Corporation, U.S.A;(4) Astronomy Unit, Queen Mary & Westfield College, U.K |
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Abstract: | Moraal and Steenberg (1999), showed that the peak energy in the anomalous cosmic ray spectra is independent of the radial
distance up to a few AU away from the termination shock but dependent on the solar wind speed, the radius of the termination
shock and the scattering strength. In this paper we will discuss the variation of the cosmic ray oxygen energy spectrum as
measured by the Ulysses EPAC and the COSPIN/LET on board Ulysses. We found that the peak energy decreased from ∼5 MeV nucl−1, when Ulysses was at high northern heliographic latitudes embedded in the fast solar wind to ∼3.5 MeV n−1, in the streamer belt. The shift towards lower energy might also be caused by changing modulation although Voyager measurements
indicate no variation of the ACR Oxygen spectrum at ∼60 AU.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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