Interrelationship of cosmic-ray anisotropies and the interplanetary magnetic field

Abstract

The direction of the cosmic ray anisotropy during solar proton events and the concurrent direction of the interplanetary magnetic field vector a r e compared using data obtained in 1966 by the Pioneer VI spacecraft. It is shown that the non-equilibrium cosmic ray anisotropy (normally observed t o exhibit an amplitude in the range 20-50%) is field aligned, while the equilibrium anisotropy (normally observed to exhibit an amplitude in the range 5-15%) is independent of the direction of the magnetic field vector. Two anomalous proton events during which pronounced anisotropies were observed with their maximum cosmic ray fluxes directed towards the sun a r e discussed. It is shown that during these proton events there were synchronous reversals of 180 in the direction of the magnetic field vector, and the cosmic ray anisotropy direction, in association with the passage of a magnetic sector boundary past the spacecraft. These observations a r e interpreted as possible evidence for their being a complex loop in the magnetic field.