Effective Geomagnetic Equator for Cosmic Radiation

Abstract

The distribution of the geomagnetic field extending far from the surface of the earth is investigated by using cosmic-ray particles as probes. Since for any longitude the cosmic-ray intensity reaches a minimum at the effective geomagnetic equator of this outer field, a series of determinations of the minimum intensity at several longitudes defines its effective equatorial plane. Measurements using the neutron intensity from the nucleonic component prove that large discrepancies exist between experimental observations and the presently accepted geomagnetic coordinates derived from surface magnetic field measurements. It is also found that meson intensity data from the past 20 years or more may be used to determine minima at other longitudes.