Relation of Frequency of Occurrence of Small Cosmic-Ray Bursts to Areas of Sunspots and Other Variables

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Abstract
This paper deals with the frequency of occurrence of small cosmic-ray bursts represented by 2.9 to 3.6 millions of pairs of ions in a heavily shielded chamber of 13.3 liters effective volume containing air at 160 atmospheres. An earlier investigation by Chree's method of superposed epochs had indicated 27-day recurrences in fluctuations of the frequency, somewhat comparable to the 28-day recurrences found in the cosmic-ray intensity as represented by the daily average ionization current in the same chamber corrected for bursts and for variations in atmospheric pressure. Here the analysis is continued to investigate the possibility of a dependence of the small-burst frequency upon terrestrial magnetic character and sunspot area comparable to that found for the C-R intensity, as well as the relation between the latter and the burst frequency. While some positive correlation between the burst frequency and the corrected ionization current is indicated, the relation does not appear to be intimate. Pulses in the burst frequency representing deviations of more than seven percent from the mean are found associated with the primary pulses in sunspot area, particularly the negative pulse, and roughly in phase opposition. No clear-cut relation to the magnetic character is indicated. A large negative barometric coefficient is found for the burst frequency, at least for the early months of the year, amounting to about -3 or -4 percent per mm Hg. An explanation of the observations is suggested in terms of the production of the small bursts and the (corrected) ionization in the shielded chamber through the agency of different types of radiation.