IQSY‐EQEX cosmic‐ray expedition to India

Traditionally, the study of cosmic radiation has involved problems in geographical distribution, and the studies carried out during the recent “EQEX” expedition are no exception. The necessity of such studies comes about since the primary cosmic radiation is a mixed radiation with a wide energy spectrum. If one wishes to study the effects of some one portion of this spectrum, it is possible to use the earth’s magnetic field as a magnetic spectrograph to sort out certain energy intervals of the radiation. By this means one can narrow down the energy‐intervals, at least to some extent. It has therefore been customary to make observations at various latitudes. The latitude of southern India is one which restricts the incident radiation to the band of incident primary energies in excess of about 15 GeV, the so‐called “Stoermer cutoff” here. Since the geomagnetic equator is north of the geographic equator at these longitudes, in India one is some eight or ten degrees further south geomagnetically than geographically.