Abstract
The nature of high energy nuclear interactions produced in photographic emulsions was investigated in the stratosphere. Examples are given, which were selected to show the principal modes of interactions, which lead to the emission of groups of particles with ionization energy losses corresponding to the minimum value for singly charged particles. For cases in which more than two particles of minimum ionization were emitted, the incident particle was found to be charged in nearly every case. The angular distribution of emitted minimum ionization tracks was measured as a function of the angle with the direction of the incident track. The zenith angle distribution of incident particles producing groups of minimum ionization tracks is given for two different altitudes in the stratosphere.