Radial and latitudinal intensity gradients of galactic and anomalous cosmic rays in the outer heliosphere

Abstract

The basic one~@~Sdimensional transport model gives the equation, gr=CVSW/~Zrr where C is the Compton-Getting factor, VSW is the solar wind velocity and ~Zrr is thee radial diffusion coefficient. In the inner heliosphere near the ecliptic plane ~Zrr iss dominated by the parallel diffusion with transition to perpendicular diffusion at near 10 AU in the outer heliosphere. In an accompanying paper we measure in detail the gradients in the inner heliosphere. In this paper we focus on the radial and latitudinal intensity gradients near the ecliptic plane in the outer heliosphere, where the perpendicular diffusion dominates, to study in more detail the gradients throughout the inner and outer heliosphere together. We assumed the radial gradients to be dependent on heliocentric radial distance r with a functional form of gr=dJ/Jdr=G0rα and the latitudinal gradients Gλ constant in heliolatitude, and measured the gradients in detail, using the combined data set observed in the solar activity minima of 1977/1997 (qA>0). The obtained gradients are discussed in comparison with those of the 1987 solar minimum(qA<0) and of 1980-81 and 1990 solar maxima.