The intensity of heavy nuclei in the primary cosmic rays over Texas in March 1962 and the solar cycle modulation

Abstract

The intensities of heavy nuclei with Z ≥ 6 in the primary cosmic radiation were measured with a nuclear emulsion stack exposed in a balloon flight over Texas on March 26-27, 1962, and the intensities of M(6 ≤ Z ≤ 9) and H(Z ≥ 10) nuclei extrapolated to the top of the atmosphere were found to be 6.20 ± 0.46 and 2.02 ± 0.25 particles/m² ster sec, respectively. Results of this work and those of other investigations made during the last solar cycle (1954-1964) are used to study the long-term solar modulation of primary S nuclei (Z ≥ 6) of rigidity ≥ 4.8 bv. It is found that the lag between the primary intensity changes and the sunspot number is about one and one-half years during the increasing phase of solar activity and is very small during the declining phase of solar activity.