Dl. Hall et al., THE NORTH-SOUTH ANISOTROPY AND THE RADIAL DENSITY GRADIENT OF GALACTIC COSMIC-RAYS AT 1 AU, Publications of the Astronomical Society of Australia, 12(2), 1995, pp. 153-158
The radial density gradient (G(r)) of Galactic cosmic rays in the ecli
ptic plane points outward from the Sun. This indicates an increasing d
ensity of cosmic ray particles beyond the Earth's orbit. Due to this g
radient and the direction of the Sun's interplanetary magnetic field (
IMF) above and below the IMF wavy neutral sheet, there exists an aniso
tropic flow of cosmic ray particles approximately perpendicular to the
ecliptic plane (i.e. in the direction parallel to B-IMF X G(r)) This
effect is called the north-south anisotropy (zeta(NS)) and manifests a
s a diurnal variation in sidereal time in the particle intensity recor
ded by a cosmic ray detector. By analysing the yearly averaged siderea
l diurnal variation recorded by five neutron monitors and six muon tel
escopes from 1957 to 1990, we have deduced probable values of the aver
age rigidity spectrum and magnitude of zeta(NS). Furthermore, we have
used determined yearly amplitudes of zeta(NS) to infer the magnitude o
f G, for particles with rigidities in excess of 10 GV.