  The interesting possibility of measuring the masses of high energy cosmic ray
particles by observing pairs of extensive air showers arriving at the earth
nearly simultaneously was proposed some years ago by Gerasimova and Zatsepin
(1960). Such showers would be created by the nuclear fragments originating as a
result of the photodisintegration of massive nuclei interacting with the solar
radiation field. In this paper we re-visit this possibility in the context of
existing and proposed detectors of high and ultra-high energy cosmic rays
considering a simple, yet realistic, model of the interplanetary magnetic
field. The possibilty of observing the mass fragmentation of cosmic rays
directly, however, remains challenging.
