[Haasbroek 1995 a]

Long-Term Cosmic-Ray Modulation along the Ulysses Trajectory:
A Numerical Simulation

L. J. Haasbroek, M. S. Potgieter und G. Wibberenz.
Long-Term Cosmic-Ray Modulation along the Ulysses Trajectory: A Numerical Simulation
Proceedings of the 24th International Cosmic Ray Conference 4, 768-771. 1995

Contents

The authors present different long-term modulation profiles for cosmic-ray protons along the Ulysses trajectory as given by a comprehensive modulation model that includes diffusion, convection, drifts and adiabatic energy losses. Scenarios for different radial and latitudinal dependences of the parallel and perpendicular diffusion coefficients are investigated. Taking into account recent Ulysses data, the autors make preliminary conclusions about the most probable spatial dependence for the above mentioned coefficients.
  1. Using diffusion coefficients proportional 1/Bm does not work. Even the strongest possible theoretically justifiable modifications to the interplanetary magnetic field seem inadequate.
  2. The R dependence for kparallel on the other hand, seems to be too strong. One should therefore consider a spatial dependence for kparallel between 1/Bm and R.
  3. Time-dependent variations should be super-imposed on the spatial variations to qualitatively explain the observed long-term profile.
  4. Generally speaking however, it is possible to obtain reasonable compatibility with data by only altering the assumptions the model is based on and not the basics of heliospheric cosmic-ray transport.

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