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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 84 (1982), S. 519-533 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Numerical solutions of the well-known spherically-symmetric transport equation for interstellar cosmic rays in the interplanetary medium are presented. It is shown: (a) why nuclei and electron modulations differ, (b) that it is easy to read more in the model than it contains, (c) that the only significant parameter that determines the level of modulation is the product of the solar wind speed and the number of diffusion mean free paths between observer and boundary, and (d) that observations do exist which cannot be explained in terms of this simple model.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 83 (1998), S. 147-158 
    ISSN: 1572-9672
    Keywords: Cosmic rays ; modulation ; heliosphere ; solar activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Almost all theoretical and numerical models for the modulation of cosmic ray in the heliosphere are based on Parker's transport equation which contains all the important basic physical processes. The relative importance of the various mechanisms is however not established and may vary significantly over 22 years. The simultaneous measurements of solar wind parameters, heliospheric magnetic field properties and cosmic rays over a wide range of energies and positions in the heliosphere have brought the realization that modulation is much more complicated than what the original drift models predicted. In the process the sophistication of models based on solving Parker's equation has increased by orders of magnitude. A short review of the global modulation of cosmic rays is given from a theoretical and modelling point of view.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The global processes that determine cosmic ray modulation are reviewed. The essential elements of the theory which describes cosmic ray behavior in the heliosphere are summarized, and a series of discussions is presented which compare the expectations of this theory with observations of the spatial and temporal behavior of both galactic cosmic rays and the anomalous component; the behavior of cosmic ray electrons and ions; and the 26-day variations in cosmic rays as a function of heliographic latitude. The general conclusion is that the current theory is essentially correct. There is clear evidence, in solar minimum conditions, that the cosmic rays and the anomalous component behave as is expected from theory, with strong effects of gradient and curvature drifts. There is strong evidence of considerable latitude transport of the cosmic rays, at all energies, but the mechanism by which this occurs is unclear. Despite the apparent success of the theory, there is no single choice for the parameters which describe cosmic ray behavior, which can account for all of the observed temporal and spatial variations, spectra, and electron vs. ion behavior.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 72 (1995), S. 385-390 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Modulation models based on the numerical solution of Parker's transport equation for galactic cosmic rays in the heliosphere make clear predictions about modulation in the high latitude heliosphere. However, for these predictions certain assumptions have to be made, for example, what the heliospheric magnetic field (HMF) looks like above the solar poles and what the spatial dependence of the diffusion coefficients are. For this presentation the general predictions of a standard drift model for the modulation of cosmic rays in the high latitude heliosphere, in particular predictions for the Ulysses trajectory, are discussed and critically reviewed. Preliminary results from Ulysses show a significant increase in the solar wind speed towards higher latitudes. The effects of this strong latitudinal dependence together with different modifications of the HMF at these high latitudes on the apparently too large diffusion and drifts predicted by current models are also shown.
    Type of Medium: Electronic Resource
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