Asymptotic cones of acceptance of cosmic ray neutron monitors in a geomagnetic field distorted by the solar wind

Abstract

The concept of an asymptotic cone of acceptance of a cosmic ray neutron monitor has been widely used during the past few years for the study of spatial anisotropies in cosmic radiation in interplanetary space [Rose and Lapointe, 1961; McCracken, 1962; Rao et al., 1963; Lockwood and Razdan, 1963]. This cone is defined as the solid angle containing the asymptotic directions of approach of cosmic ray particles outside the influence of the geomagnetic field that significantly contribute to the counting of a ground detector [McCracken, 1959]. Knowing these cones at various stations, one can relate the intensity observed at a particular time to a direction in space outside the magnetosphere. So far, these cones have been calculated for the quiet geomagnetic field conditions for a simple dipole model of the earth [Lapointe and Rose, 1961] and for a high degree simulation of the geomagnetic field [McCracken, 1962; McCracken et al., 1962].