26Al and 53Mn produced by solar-flare particles in lunar rock and cosmic dust

With the use of the excitation functions for 26Al-producing reactions measured by us, the rates of 26Al production in interplanetary targets (lunar rocks 10017 and 12002 and cosmic dust) by solar-flare particles have been calculated. The same calculations have also been made for 53Mn with the estimated excitation functions. The energy spectrum of solar protons averaged over the 1956–1966 solar cycle was used as a guide for the unknown flux over the last few million years with the assumption that the ratio of H/He was 6. It is shown that the half-value of the average flux reproduces rather well the observed depth profiles of these nuclides in the lunar rocks and the observed limit of 26Al in marine sediment. A slight discrepancy between the calculated and the observed pattern of 53Mn at the top surface of lunar rocks is discussed in terms of surface erosion and other effects. The present calculations are compared with earlier ones.