Physics
Scientific paper
May 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agusmsh31a..05p&link_type=abstract
American Geophysical Union, Spring Meeting 2002, abstract #SH31A-05
Physics
7843 Numerical Simulation Studies, 2104 Cosmic Rays
Scientific paper
It is a difficult task to construct a theory of modulation using a diffusion tensor based upon ab initio turbulence and scattering theories. We employ direct numerical solutions of the steady state cosmic ray trnsport equation to examine important factors which affect modulation. Both observational and physical issues concerning scattering and turbulence enter into the calculation. Introducing a new perpendicular diffusion formalism which smoothly varies between the field line random walk limit and a recent treatment based upon the Taylor--Green--Kubo equation, we study whether modulation is dominated, in a relatve sense, by drift or diffusion. There seems to evolve a pattern governing such trend when magnetic correlation length or an outer scale of turbulence, the ``ultrascale", is appropriately changed. The effects of ultrascale in inner and outer heliosphere are also discussed. Comparison is made with latest observational data from Voyager, Ulysses and IMP for radial profiles of 200 MeV protons in the equatorial plane and latitudinal gradient. Though there is a good fit with radial profile it becomes difficult to fit both radial profile and latitudinal gradient data to the same degree of accuracy. The simulation suggests that there is very little perpendicular diffusion in outer heliosphere consistent with the observation.
Bieber John W.
Burger R. A.
Matthaeus William H.
Parhi S.
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