Atmospheric Effects on Cosmic Radiation, Air-mass Absorption and Meson Decay

The percentage variations of twenty-four hour means of C. R. in Stockholm (magn. lat 58°) amount to ± 5% of the mean value over a quiet period of two months' duration. The two atmospheric effects, the mass absorption due to ionisation and the meson decay, contribute ± 4%. The residual variations, in excess of statistical fluctuations of 0.1%, depend upon other factors, such as geomagnetic activity and solar influences.

The true absorption coefficient for zenith radiation (β) is calculated to have a value of 1.27 · 10^–3 cm²/g and the rate of decay (β′) is found to be about 0.060 pr km. The meson producing layer is attributed to the 200 mb surface, the highest level reached by the daily radiosonde ascents in Stockholm.

The most reliable decay value is obtained by considerations of the thermal structure of air-mass changes in travelling deep depressions.