ATMOSPHERIC ELECTRICITY AT THE COLLEGE‐FAIRBANKS POLAR YEAR STATION

Abstract

The atmospheric‐electric program at College, Alaska, during the second International Polar Year extended from October 1, 1932, to August 31, 1933. (1) Continuous registration was made of air‐potential with a recording quadrant‐electrometer and a radioactive collector on a horizontal rod at the variation‐observatory and during most of the time also with a recording bifilar‐electrometer with radioactive collectors exposed by the stretched‐wire method for control at a standardization‐station. (2) Continuous registration was made of air‐conductivity due to both positive and negative ions, using semi‐portable apparatus in which the deflection is nearly proportional to the conductivity; in this apparatus the charge collected by the Gerdien condenser flows to earth through a resistance of about one electrostatic unit and the resulting voltage‐drop through this unit is recorded by a single‐fiber electrometer. (3) Determinations of the number of positive and negative small ions, usually made once each day, using a modified Ebert ion‐counter. (4) Determinations of the number of condensation‐nuclei, once daily from late in March through August, using an Aitken counter; during the cold weather the counter did not function satisfactorily.These data conform with those obtained in lower latitudes at stations on land that are relatively free from variable sources of pollution. The average gradient for all complete days for the eleven‐month period is 104 volts per meter with a maximum in January and a minimum in August. Harmonic analyses of the hourly values show that a 24‐hour component exists in gradient, in substantial agreement with Mauchly's findings. All complete days of positive and negative conductivity yield average values of 179 and 131 × 10−6 electrostatic unit, respectively. The variations are approximately the inverse of those in the gradient although their product—the electrical conduction current—shows regular daily and seasonal variations. The average number of positive small ions by months varied from a minimum of 620 per cc in July to a maximum of 980 in November. The number of negative small ions varied from 520 per cc in July to 660 in November and February. From the ion‐count and the corresponding values of conductivity a mean value of 1.56 cm2 volt−1 sec−1 for the mobility of both the positive and negative small ions was found, although different mobility‐groups are indicated by frequency‐curves. The average of 112 determinations of nuclei is 3760 per cc.The electrode‐effect appears to be quite important at this station. The ratio of positive to negative conductivity varies directly as the gradient, both in long‐period and short‐period changes. This and other features of the results are explicable on the basis of conditions as they would exist in quiet air. At times turbulence is effective in complicating the relations between the elements and so for a complete explanation of these results the effect of mixing must be considered in addition to conditions as they would exist in quiet air.