Condensation‐nuclei in the atmosphere at the Huancayo Magnetic Observatory, Peru, and their relation to atmospheric‐electric and meteorological observations

Measurements of condensation‐nuclei near the ground were made daily with an Aitken pocket counter from June 1, 1934, to December 31, 1936. Simultaneous observations were made of potential‐gradient and conductivity of the atmosphere, and daily records were kept of rainfall. The data are grouped in monthly means for discussion. In the dry season, when there are only a few days on which rain falls each month, the nuclei are numerous, averaging more than 20,000 per cc, while in the wet season, when there is some rain nearly every day, the average is less than 10,000 per cc. The conductivity of the atmosphere responds to the change in nuclei‐concentration, being conspicuously higher when nuclei are few than when they are numerous. Potential‐gradient shows less response than conductivity to changes in nuclei‐concentration, but in general shows a variation similar to that for nuclei. Computed values of air‐earth current show definite response to changes in nuclei‐content, being smallest when the nuclei are most numerous. This suggests that nuclei exist in sufficient quantities and to such heights above the Observatory as to significantly affect the total resistance of the atmosphere there. Detailed study of the daily observations in the dry month of June in all three years give added support to these conclusions. The data for the three June months are subjected to analysis on the basis of formulas proposed by F.J.W. Whipple and H.L. Wright for determining the size of the nucleus and the combining‐coefficients, η1 and η0, for charged and uncharged nuclei with small ions. The rate of production of small ions is assumed to be ten pairs per cc per second. The radius of the nucleus varies only between 1×10−6 and 3×10−6 cm when nuclei are more numerous than 10,000 per cc. For few nuclei, 1000 or 2000 per cc, the radius becomes 12×10−6 cm. These values of the radius are uncertain to 20 or 30 per cent, depending on the validity of various assumptions in the calculations. Values of η1 and η0 decrease rapidly with increase in nuclei up to 10,000 nuclei per cc. Thereafter η0 is comparatively small (less than 1×10−6) and η1 may be regarded as constant at about 2.5×10−6. Less than one‐fifth of the nuclei are charged, of one sign, when the concentration is greater than 10,000 per cc.