THE NORTH-SOUTH ANISOTROPY AND THE RADIAL DENSITY GRADIENT OF GALACTIC COSMIC-RAYS AT 1 AU

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.