The cosmic-ray equator and the Earth's magnetic field

The positions of the cosmic-ray intensity minimum off the west coast of Africa and in the Indian Ocean, respectively, have been determined from measurements obtained with a shipboard neutron monitor during two voyages between Scandinavia and Australia. The cosmic-ray equator is in accordance with the prediction based upon calculations of modified cutoff rigidities at the first location, but differs by 4° at the second. Contemporary observations of zero magnetic dip indicate that the cosmic-ray intensity minimum coincides with the dip equator at 14°W, but differs in geographic latitude by 2° in the vicinity of 60°E.