Mean free paths and diffusion coefficients for energetic protons at small heliodistances calculated using Helios 1 and 2 data |
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| Authors: | J F Valdés Galicia X Moussas J J Quenby F M Neubauer R Schwenn |
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| Institution: | (1) Instituto de Geofisica, UNAM, 04510 Mexico, D.F., Mexico;(2) Astrophysics Laboratory, Astrophysics Astronomy and Mechanics Unit, Dept. of Physics, National University of Athens, Panepistimopolis, GR 157 71 Athens, Greece;(3) Blackett Laboratory, Imperial College, SW7 2BZ London, UK;(4) Institut für Geophysik und Meteorologie der Universität Köln, D-500 Köln, F.R.G.;(5) Max-Planck-Institut für Aeronomie, Postfach 20, D-3411 Katlenburg-Lindau, F.R.G. |
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| Abstract: | Pitch angle scattering of energetic particles (100 MeV) in the interplanetary medium are studied using Helios 1 and 2 magnetometer and plasma data during 1976 near the minimum of solar activity. An IMF configuration was used in the computer experiments which allowed the pitch angle diffusion coefficient, D
 and hence the parallel mean free path, 
 to be determined. The radial mean free path was found to vary as
r  r
-0.9 between 0.4 and 1 AU, but between 0.3 and 0.4 AU it decreases significantly. To reconcile our value of
r at 1 AU, lying between 0.01 and 0.02 AU, with the average prompt solar proton event profile, an increasing value of
r at lower radial distances would be required. |
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