The evaluation of the interplanetary diffusion coefficient for energetic particles employing real magnetic field data |
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| Authors: | X Moussas J J Quenby |
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| Institution: | (1) The Blackett Laboratory, Imperial College, London, England;(2) Present address: Astrophysics Laboratory, University of Athens, Panepistimiopolis, Athens, Greece |
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| Abstract: | A numerical simulation of energetic particle motion in the interplanetary medium is carried out using HEOS-2 magnetometer data in order to computeD( ), the pitch angle diffusion coefficient, where is cosine of pitch angle defined with respect to the local field. WhileD() exceeds that given by quasi-linear theory near 90° pitch angle, it is significantly less at higher values of , leading to a parallel transport coefficient in good accord with that given by experimental studies of solar proton propagation. In particular,   =0.031 AU at a particle magnetic rigidity of 455 MV, while experimental results range from 0.05 to 0.07 AU (+100%, –50%) in this rigidity region. Furthermore, observed approximately -dependent solar proton pitch angle distributions are consistent with the computed findingD()/(1 –
2)2 ~ constant.The validity of various analytical corrections to quasi-linear theory as  0 are also investigated numerically. |
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