Elsevier, Planetary and Space Science, 2(33), p. 147-157
DOI: 10.1016/0032-0633(85)90125-4
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The anisotropy of 35-1000 keV ions in two corotating particle events associated with high-speed solar wind streams at 1 AU is examined in terms of the diffusion-convection propagation model using data from the Energetic Proton Anisotropy Spectrometer on ISEE-3. The calculated diffusive anisotropy in the solar wind frame is found to be sunward and closely field-aligned, with a nearly energy-independent magnitude of about 40 percent. For one stream, using the Voyager 2 data of Decker et al. (1981), a positive gradient of about 100 percent/AU is found for greater than or equal to 50 keV ions between 1 and 4 AU. The observations do not appear to support the scatter-free propagation model and indicate that ions with energies as low as a few tens of keV may be in diffusive equilibrium with the solar wind in this class of events.