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Effects of particle drift on cosmic-ray transport. I - General properties, application to solar modulation
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1977
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Cosmic‑ray transport equations include gradient and curvature drifts, yet most solar‑modulation models ignore them, despite their potential importance. The authors explicitly calculate drift velocities in the Parker spiral magnetic field, showing they exceed the solar‑wind speed for particles above ~0.3 GV and demonstrate their impact on simple modulation models. These calculations reveal that drift effects dominate over solar‑wind advection for rigidities above ~0.3 GV and that omitting drifts in current models leads to an unfair comparison with observations, potentially underestimating net modulation. Published in The Astrophysical Journal (May 1977) by Jokipii, Levy, and Hubbard, DOI 10.1086/155218.
view Abstract Citations (411) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Effects of particle drift on cosmic-ray transport. I. General properties, application to solar modulation. Jokipii, J. R. ; Levy, E. H. ; Hubbard, W. B. Abstract Although gradient and curvature drifts are explicitly contained in the general equations of cosmic-ray transport, they have been almost universally neglected in applications of these equations. The drifts are evaluated explicitly for the Parker (1965) spiral magnetic field, and it is shown that for particles with rigidities greater than about 0.3 GV in the solar wind, they are larger than the solar-wind velocity over much of the heliosphere. Hence most current models of solar modulation and solar-flare particle events neglect terms which in many cases are as important as those retained. Calculations are presented which demonstrate the importance of the effects for simple modulation models. It is concluded that comparisons of presently available model calculations with observations do not provide a fair test of transport theory since they neglect drifts, which may substantially reduce the net modulation. Publication: The Astrophysical Journal Pub Date: May 1977 DOI: 10.1086/155218 Bibcode: 1977ApJ...213..861J Keywords: Particle Diffusion; Solar Cosmic Rays; Solar Flares; Solar Wind Velocity; Transport Properties; Adiabatic Conditions; Interplanetary Magnetic Fields; Particle Flux Density; Space Radiation full text sources ADS |