Ab Initio Solar Modulation of Cosmic Rays Using Improved Models of Perpendicular Diffusion and Heliospheric Turbulence

Details Ab Initio Solar Modulation of Cosmic Rays Using Improved Models of Perpendicular Diffusion and Heliospheric Turbulence Ab Initio Solar Modulation of Cosmic Rays Using Improved Models of Perpendicular Diffusion and Heliospheric Turbulence

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsh43a1096p&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #SH43A-1096

Other

2104 Cosmic Rays, 2114 Energetic Particles, Heliospheric (7514), 2134 Interplanetary Magnetic Fields, 2149 Mhd Waves And Turbulence, 2152 Pickup Ions

Scientific paper

A solar wind modulation model is discussed, implementing several recent advances, including a perpendicular diffusion coefficient computed from Nonlinear Guiding Center Theory (NLGC) [Matthaeus et al., ApJ, 590, L53, 2003], a turbulence model that includes cross helicity effects, and latitudinal variations of the boundary conditions for magnetic variance, correlation length, cross helicity and plasma temperature. The model spans from 0.3 AU to 100 AU. Also varied in this simulation are the observationally based latitudinal profiles of solar wind speed, mass flux density, and temperature [McComas et al., J. Geophys. Res., 105, 10419, 2000]. A simple model of pick-up ions is employed. In the ab initio modulation approach, the computed turbulence properties determine diffusion coefficients that appear in the numerical integration of the Parker's transport equation. A significant improvement in the cosmic ray latitudinal gradient is accomplished by using a numerical solution of the integral equation for the NLGC perpendicular diffusion coefficient. The run time for this calculation is lengthy. The modulation result thus obtained is tested with another version that implements an analytical approximation [Shalchi et al., ApJ, 604, 675, 2004] of the NLGC result. The latter implementation gives very similar results and takes significantly less time to run. Supported by NASA grant NNG04GF81G.

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