摘要：1. Introduction The first wintering party of the Japanese Antarctic Research Expedition installed itself at Syowa Base in February 1957 and remained there until February 1958 when they departed from the base. Throughout the entire period, cosmic-ray observations were performed by using a Neher type ionization chamber. This simple and handy equipment had been prepared for use by the wintering team which had no properly trained cosmic-ray physicist. However, the data thereby obtained was sufficiently accurate to permit a study of certain characteristics of cosmic-ray behavior in the Antarctic region. In this report, atmospheric effects, diurnal variations and Forbush decrease of cosmic-ray intensities (cosmic-ray storm) are discussed. 2. Atmospheric effects The data of neutron components and upper atmospheric temperatures observed at Mawson Base were used in order to find out the pressure and temperature coefficients of meson component at Syowa Base. In this case, neutron components were used as a measure of time variations of primary cosmic-ray intensities. The value of the barometric pressure coefficient thus obtained was -0 .14 ± 0. 01 J;:;/ mb (Table 2). However, in the case of seeking a temperature coefficient, it must be noticed that the distributions of atmospheric temperature against the altitude in the Antarctic region are very different from those in lower latitudes (Figs. 2, 3). Analyzing the data, the correlation coefficient of cosmic-ray intensity with 100 mb level becomes much more suitable than that of other levels and the regression coefficient for a height of 100 mb also just coincides with the value in Tokyo (Figs. 4, 5). It needs further investigations whether the phenomena mentioned above will be explained by the decay effect of meson component, or the partial temperature effect only. 3. Diurnal variations In discussing the diurnal variation of cosmic-rays, it is impossible to neglect that of the atmospheric temperature. As shown in Fig. 6, the diurnal variation of surface temperature is negligibly small during Apr. - Aug., whereas very large during Sept. - Jan. at Syowa Base. The diurnal variations of cosmic-ray intensities for both periods were shown in Fig. 7 and Table 3. If the mean diurnal variation of cosmic-rays in the latter period was corrected for atmospheric temperature by assuming that the diurnal variation of upper temperature may be the same with the one of the surface temperature, 0. 07 in Table 3 becomes to O. 32, which is nearly equal to a value in the former period. Besides, from the results of neutron component observed at Mawson Base, it is likely that the same diurnal variations of the primary csmicrays exist for both periods. These facts mean that the diurnal variation of the upper temperature does not exist during Apr. - Aug. at Syowa Base. If it is true, it is important to observe the meson component there, because the ambiguity induced from the effect of atmospheric temperature becomes negligible. 4. Forbush decreases Five remarkable decreases of cosmic-ray intensities happened during the period observed. Three of them differ from the others for the spectrum of cosmic-ray storms. It was deduced from the fact that the regression coefficients of neutron component against meson component change for the different cosmic-ray storms (Figs. 8, 9 and Table 4). This fact was ascertained also by the latitude effects of cosmic-ray storms (Fig. 10 (A) and (B)). 5. Acknowledgement The authors express their hearty thanks to Dr. N. R. PARSONS, University of Tasmania, for his prompt supply of cosmic-ray and radiozonde data observed at l\fawson Base. The present observation was much indebted to members of the first wintering team.
