The Heavy Nuclei of the Primary Cosmic Radiation

Abstract

The atmospheric absorption of the flux of nuclei of charge \ensuremath{\ge}10 has been obtained at $\ensuremath{\lambda}=55$ N from a combination of flux measurements at different altitudes and at different zenith angles. The absorption, together with the collision cross section, gives an energy spectrum consistent with the one measured by stopping particles and the latitude effect. The cross section for collision of heavy nuclei is about three-fourths of the geometric cross section. The energy spectrum can be represented by $\mathrm{NE}>{E}_{0}\ensuremath{\propto}\frac{1}{E_{0}^{\ensuremath{\gamma}}}$, where $\ensuremath{\gamma}$ is 0.5 for energies above 0.8 Bev/nucleon. $N$ is the number of nuclei with an energy greater than ${E}_{0}$ per nucleon. The flux measured at $\ensuremath{\lambda}=30$ N gives an exponent $\ensuremath{\gamma}=0.5$. At energies below about 0.75 Bev/nucleon the spectrum seems to get steeper. The flux of heavy nuclei measured on two night flights shows no significant difference from the day flux. Solar activity resulting in flares of importance 1 and 2 shows no measurable correlation with flux of heavy nuclei.