Cosmic-ray perpendicular diffusion coefficient computed using Voyager data at 15 AU |
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| Authors: | J F Valdes-Galacia J J Quenby X Moussas |
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| Institution: | (1) Instituto de Geofisica, UNAM, 04510 Mexico D.F., Mexico;(2) Imperial College, SW7 2BZ London, UK;(3) Astrophysics Lab. University of Athens, GR 15783 Panepistimiopolis, Athens, Greece |
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| Abstract: | Perpendicular diffusion due to either field line wandering or random gradient and curvature effects makes a substantial contribution to the radial transport of particles at distances of about 5 AU and beyond when lines of the interplanetary magnetic field (IMF) become almost azimuthal. Here test particle trajectories are followed in a field model which uses a magnetic field sample taken by Voyager 2 at 14.8 AU. Techniques previously developed (Moussas et al., 1982a) are employed to calculate the perpendicular diffusion coefficient for 100 MeV protons and arising from random gradient and curvature effects. The result K =(2.8±0.9)×1021 cm2 s–1 shows a substantial increase above the value determined previously at 5 AU and, assuming a power law radial dependence K r
 , implies  0.8–1.1. This result is consistent with observations of the cosmic-ray radial gradient. |
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