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Persistent Sunward Flow of ~1.6 MeV Protons at 1 AU

Marshall, F. E. and Stone, E. C. (1977) Persistent Sunward Flow of ~1.6 MeV Protons at 1 AU. Geophysical Research Letters, 4 (1). pp. 57-60. ISSN 0094-8276. doi:10.1029/GL004i001p00057.

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It has been found that except during the onset of prompt solar particle events the diffusive flow of 1.3 to 2.3 MeV protons at 1 AU is predominantly sunward. The anisotropy of the proton intensity has been measured with the Caltech Electron/Isotope Spectrometer aboard IMP-7 for periods between prompt solar particle events from 72/273 to 74/2. The diffusive anisotropy, which has been determined by subtracting the independently determined convective anisotropy from the observed anisotropy, is predominantly directed toward the sun with a mean radial component of 14%. This sunward diffusion is typical of intensities from 0.012 to 1.2 (cm^² sec sr MeV)^(−1) for 1.3 - 2.3 MeV protons and indicates that a positive radial gradient is characteristic of these modestly enhanced fluxes. The direction of the flow is opposite to that which would be produced by previously proposed models which involve a continuous solar source for the observed particles. A steady-state propagation model which includes adiabatic energy loss with particle injection beyond 1 AU produces the average observed anisotropy for κ_rr∼4 × 10^20 cm^² sec^(−1).

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Stone, E. C.0000-0002-2010-5462
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Additional Information:Copyright 1977 by the American Geophysical Union. (Received October 18, 1976; accepted November 11, 1976.) We are grateful to H. S. Bridge and J. D. Sullivan for providing IMP-7 plasma data prior to publication. We are also grateful to R. E. Vogt who has been intimately involved throughout the IMP-7 program. Significant contributions to this project have also been made by W. E. Althouse, G. J.Hurford, and R. A. Mewaldt. This work was supported in part by the National Aeronautics and Space Administration under Contract NAS5-11066 and Grant NGR 05-002-160. F. E. Marshall has received valuable sup port from an NDEA Fellowship.
Group:Space Radiation Laboratory
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NASANGR 05-002-160
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Space Radiation Laboratory1976-04
Issue or Number:1
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ID Code:44882
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Deposited On:11 Apr 2014 16:39
Last Modified:10 Nov 2021 16:57

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