Study of Cosmic Ray Produced Short-Lived P<sup>32</sup>, P<sup>33</sup>, Be<sup>7</sup>, and S<sup>35</sup> in Tropical Latitudes

Abstract

The fall-out rate of four short-lived isotopes P32, P33, Be7 and S35, produced in the collisions of cosmic ray particles with air nuclei, has been measured at a number of stations in India and compared with the calculated rate of production. In the case of Be7, the agreement between the calculated and measured values is good. The fall-out rates of P32 and P33 are not inconsistent with the calculated values; that of S35, however, is about five times higher than expected. The absolute concentrations of an individual isotope in various rain falls have been found to vary by more than a factor of forty; relative concentrations of the different isotopes, however, stayed within fairly narrow limits. The ratio of the concentration of the isotope Be7 to that of the isotope P32 in individual rain samples has been used to find out the periods for which various air masses had been irradiated in the interval between two successive precipitations. The mean period of irradiation is found to be about thirty-five days. Our results are consistent with the view that, in these tropical latitudes, intrusions of stratospheric air into the troposphere are either rare or weak in intensity. The method seems capable of further development as a tool for studying meteorological problems.